{"collection":"philosophy-ethics","full_text_available":true,"graph_url":"https://unchartedknowledge.5gfusion.net/v2/api/page/gutenberg_65699/graph","html_url":"https://unchartedknowledge.5gfusion.net/v2/page/gutenberg_65699","id":"gutenberg_65699","license":"Public Domain (US)","rights_basis":"gutenberg_metadata_copyright_false","source":"gutenberg","source_url":"https://www.gutenberg.org/ebooks/65699","summary":null,"tags":["Category: Philosophy & Ethics","Category: Science - Biology","Life (Biology)"],"text":"Transcriber\u2019s Notes\n\nObvious typographical errors have been silently corrected. Variations\nin hyphenation and accents have been standardised but all other\nspelling and punctuation remains unchanged.\n\nIn the section on The Instinct of Life, fifth paragraph \u201cand Flourens\nhas reduced the ratio to that of 5:1, which would still give us 120\nyears.\u201d the 120 has been corrected to 100.\n\nIn Book V, Chapter III, Chemical Changes, \u201cand at the same time would\ntransform an amido-group into an amido-group.\u201d is as printed.\n\nItalics are represented thus _italic_, superscripts thus y^ and\nsubscripts thus y\u2304.\n\n\n\n\n LIFE AND DEATH.\n\n\n\n\n LIFE AND DEATH\n\n BY\n\n A. DASTRE,\n PROFESSOR OF PHYSIOLOGY AT THE SORBONNE.\n\n TRANSLATED BY\n W. J. GREENSTREET, M.A., F.R.A.S.\n\n THE WALTER SCOTT PUBLISHING CO., LTD.,\n PATERNOSTER SQUARE, LONDON, E.C.\n CHARLES SCRIBNER\u2019S SONS,\n 153-157 FIFTH AVENUE, NEW YORK.\n 1911\n\n\n\n\n PREFACE.\n\n\nThe educated and inquiring public of the present day addresses to the\nexperts who have specialized in every imaginable subject the question\nthat was asked in olden times of Euclid by King Ptolemy Philadelphus,\nProtector of Letters. Recoiling in dismay from the difficulties\npresented by the study of mathematics and annoyed at his slow progress,\nhe inquired of the celebrated geometer if there was not some royal\nroad, could he not learn geometry more easily than by studying the\nElements. The learned Greek replied, \u201cThere is no royal road.\u201d These\nroyal roads making every branch of science accessible to the cultivated\nmind did not exist in the days of Ptolemy and Euclid. But they do exist\nto-day. These roads form what we call Scientific Philosophy.\n\nScientific philosophy opens a path through the hitherto inextricable\nmedley of natural phenomena. It throws light on facts, it lays bare\nprinciples, it replaces contingent details by essential facts. And\nthus it makes science accessible and communicable. Intellectually it\nperforms a very lofty function.\n\nThere is virtually a philosophy of every science. There is therefore\na philosophy of the science which deals with the phenomena of life\nand death\u2014_i.e._, of physiology. I have endeavoured to give a summary\nof this philosophy in this volume. I have had in view two classes of\nreaders. In the first place there are readers of general culture who\nare desirous of knowing something of the trend of ideas in biology.\nThey already form quite a large section of the great public.\n\nThese scholars and inquirers, with Bacon, believe that the only science\nis general science. What they want to know is not what instruments we\nuse, our processes, our technique, and the thousand and one details of\nthe experiments on which we spend our lives in the laboratory. What\nthey are interested in are the general truths we have acquired, the\nproblems we are trying to solve, the principles of our methods, the\nprogress of our science in the past, its state in the present, its\nprobable course in the future.\n\nBut I venture to think that this book is also addressed to another\nclass of readers, to those whose professional study is physiology.\nTo them it is dedicated. They have been initiated into the mysteries\nof the science. They are learning it by practice. That is the right\nmethod. Practice makes perfect. Claude Bernard used to say that in\norder to be an expert in experimental science you must first be \u201ca\nlaboratory rat.\u201d And among us there are many such \u201claboratory rats.\u201d\nThey are guided in the daily task of investigation by a dim instinct\nof the path and of the direction of contemporary physiology. Perhaps\nit may be of assistance to them to find their more or less unconscious\nideas here expressed in an explicit form.\n\n A. DASTRE.\n\n\n\n\n CONTENTS.\n\n\n BOOK I.\n\n THE FRONTIERS OF SCIENCE. GENERAL THEORIES OF\n LIFE AND DEATH. THEIR SUCCESSIVE TRANSFORMATIONS.\n\n CHAP. PAGE\n\n I. EARLY THEORIES 1\n\n II. ANIMISM 5\n\n III. VITALISM 15\n\n IV. THE MONISTIC THEORY 34\n\n V. THE EMANCIPATION OF SCIENTIFIC RESEARCH FROM\n THE YOKE OF PHILOSOPHICAL DOCTRINE 42\n\n\n BOOK II.\n\n THE DOCTRINE OF ENERGY AND THE LIVING WORLD.\n GENERAL IDEAS OF LIFE. ALIMENTARY LIFE.\n\n I. ENERGY IN GENERAL 57\n\n II. ENERGY IN BIOLOGY 97\n\n III. ALIMENTARY ENERGETICS 116\n\n\n BOOK III.\n\n THE CHARACTERS COMMON TO LIVING BEINGS.\n\n I. DOCTRINE OF VITAL UNITY 146\n\n II. MORPHOLOGICAL UNITY OF LIVING BEINGS 157\n\n III. CHEMICAL UNITY OF LIVING BEINGS 173\n\n IV. TWOFOLD CONDITIONS OF VITAL PHENOMENA.\n IRRITABILITY 188\n\n V. THE SPECIFIC FORM: ITS ACQUISITION, ITS REPARATION 199\n\n VI. NUTRITION. FUNCTIONAL ASSIMILATION. FUNCTIONAL\n DISTRIBUTION. ASSIMILATING SYNTHESIS 209\n\n\n BOOK IV.\n\n THE LIFE OF MATTER.\n\n I. UNIVERSAL LIFE (OPINIONS OF THE PHILOSOPHERS\n AND POETS). CONTINUITY BETWEEN BRUTE BODIES\n AND LIVING BODIES. ORIGIN OF THE PRINCIPLE OF\n CONTINUITY 239\n\n II. ORIGIN OF LIVING MATTER IN BRUTE MATTER 249\n\n III. ORGANIZATION AND CHEMICAL COMPOSITION OF LIVING\n MATTER AND BRUTE MATTER 255\n\n IV. EVOLUTION AND MUTABILITY OF LIVING MATTER AND\n BRUTE MATTER 259\n\n V. THE COMPOSITION OF THE SPECIFIC FORM. LIVING\n BODIES AND CRYSTALS. CICATRIZATION 281\n\n VI. NUTRITION IN THE LIVING BEING AND IN THE\n CRYSTAL 290\n\n VII. GENERATION IN BRUTE BODIES AND LIVING BODIES.\n SPONTANEOUS GENERATION 294\n\n\n BOOK V.\n\n SENESCENCE AND DEATH.\n\n I. THE DIFFERENT POINTS OF VIEW FROM WHICH DEATH\n MAY BE REGARDED 307\n\n II. CONSTITUTION OF THE ORGANISMS. PARTIAL DEATH.\n COLLECTIVE DEATHS 312\n\n III. PHYSICAL AND CHEMICAL CHARACTERISTICS OF\n CELLULAR DEATHS. NECROBIOSIS 321\n\n IV. APPARENT PERRENNITY OF COMPLEX INDIVIDUALS 330\n\n V. IMMORTALITY OF THE PROTOZOA AND OF SLIGHTLY\n DIFFERENTIATED CELLS 334\n\n VI. LETHALITY OF THE METAZOA AND OF DIFFERENTIATED\n CELLS 340\n\n VII. MAN. THE INSTINCT OF LIFE AND THE INSTINCT OF\n DEATH 345\n\n INDEX 361\n\n\n\n\n LIFE AND DEATH.\n\n BOOK I.\n\n THE FRONTIERS OF SCIENCE\u2014GENERAL THEORIES OF LIFE AND DEATH\u2014THEIR\n SUCCESSIVE TRANSFORMATIONS.\n\n Chapter I. Early Theories.\u2014II. Animism.\u2014III. Vitalism.\u2014IV. Monism.\u2014V.\n Emancipation of Scientific Research from the Yoke of Philosophy.\n\n\n CHAPTER I.\n\n EARLY THEORIES.\n\n Animism\u2014Vitalism\u2014The Physico-Chemical Theory\u2014Their Survival and\n Transformations.\n\n\nThe fundamental theories of science are but the expression of its\nmost general results. What, then, is the most general result of the\ndevelopment of physiology or biology\u2014that is to say, of that department\nof science which has life as its object? What glimpse do we get of the\nfruit of all our efforts? The answer is evidently the response to that\nessential question\u2014What is Life?\n\nThere are beings which we call living beings; there are bodies which\nhave never been alive\u2014inanimate bodies; and there are bodies which are\nno longer alive\u2014dead bodies. The fact that we use these terms implies\nthe idea of a common attribute, of a _quid proprium_, life, which\nexists in the first, has never existed in the second, and has ceased\nto exist in the last. Is this idea correct? Suppose for a moment that\nthis is so, that this implicit supposition has a foundation, and that\nthere really is something which corresponds to the word \u201c_life_.\u201d Must\nwe then wait for the last days of physiology, and in a measure for its\nlast word before we know what is hidden behind this word, \u201clife\u201d?\n\nYes, no doubt positive science should be precluded from dealing with\nquestions of this kind, which are far too general. It should be limited\nto the study of second causes. But, as a matter of fact, scientific men\nin no age have entirely conformed to this provisional or definitive\nantagonism. As the human mind cannot rest satisfied with indefinite\nattempts, or with ignorance pure and simple, it has always asked, and\neven now asks, from the spirit of system the solution which science\nrefuses. It appeals to philosophical speculation. Now, philosophy, in\norder to explain life and death, offers us hypotheses. It offers us\nthe hypotheses of thirty, of a hundred, or two thousand years ago.\nIt offers us animism; vitalism in its two forms, unitary vitalism\nor the doctrine of vital force, and dismembered vitalism or the\ndoctrine of vital properties; and finally, materialism, a mechanical\ntheory, unicism or monism,\u2014to give it all its names\u2014_i.e._, the\nphysico-chemical doctrine of life. There are, therefore, at the present\nday, in biology, representatives of these three systems which have\nnever agreed on the explanation of vital phenomena\u2014namely, animists,\nvitalists, and monists. But it is pretty clear that there must have\nbeen some change between yesterday and to-day. Not in vain has general\nscience and biology itself made the progress which we know has been\nmade since the Renaissance, and especially during the course of the\nnineteenth century. The old theories have been compelled to take new\nshape, such parts as have become obsolete have been cut away, another\nlanguage is spoken\u2014in a word, the theories have become rejuvenated. The\nneo-animists of our day, Chauffard in 1878, von Bunge in 1889, and more\nrecently Rindfleisch, do not hold exactly the same views as Aristotle,\nSt. Thomas Aquinas, or Stahl. Contemporary neo-vitalists, physiologists\nlike Heidenhain, chemists like Armand Gautier, or botanists like Reinke\ndo not between 1880 and 1900 hold the same views as Paracelsus in\nthe fifteenth century and Van Helmont in the seventeenth, as Barthez\nand Bordeu at the end of the eighteenth, or as Cuvier and Bichat at\nthe beginning of the nineteenth century. Finally, the mechanicians\nthemselves, whether they be disciples of Darwin and Haeckel, as\nmost biologists of our own time, or disciples of Lavoisier, as most\nphysiologists of the present day, have passed far beyond the ideas of\nDescartes. They would reject the coarse materialism of the celebrated\nphilosopher. They would no longer consider the living organism as a\nmachine, composed of nothing but wheels, springs, levers, presses,\nsieves, pipes, and valves; or again of matrasses, retorts, or alembics,\nas the iatro-mechanicians and would-be chemists of other days believed.\n\nAll that is changed, at any rate in form. If we look back only thirty\nor forty years we see that the old doctrines have undergone more or\nless profound modifications. The changes of form, which have been\nmade necessary by the acquisitions of contemporary science, enable us\nto appreciate its progress. They enable us to give an account of the\nprogress of biology, and for this reason they deserve to be examined\nwith some attention. It is into this examination that I ask my readers\nto accompany me.\n\n\n\n\n CHAPTER II.\n\n ANIMISM.\n\n The Common Characteristic of Animism and Vitalism: the Human\n Statue\u2014Primitive Animism\u2014Stahl\u2019s Animism\u2014First Objection with\n Reference to the Relation between Soul and Body\u2014Second Objection: the\n Unconscious Character of Vital Operations\u2014Twofold Modality of the\n Soul\u2014Continuity of the Soul and Life.\n\n\nChildren are taught that there are three kingdoms in Nature\u2014the mineral\nkingdom and the two living kingdoms, animal and vegetable. This is the\nwhole of the sensible world. Then above all that is placed the world of\nthe soul. School-boys therefore have no doubts on the doctrines that we\ndiscuss here. They have the solution. To them there are three distinct\nspheres, three separate worlds\u2014matter, life, and thought.\n\nIt is this preconceived idea that we are about to examine. Current\nopinion solves _a priori_ the question of the fundamental homogeneity\nor lack of resemblance of these three orders of phenomena\u2014the phenomena\nof inanimate nature, of living nature, and of the thinking soul.\n_Animism_, _vitalism_, and _monism_ are, in reality, different ways of\nlooking at them. They are the different answers to this question:\u2014Are\nvital, psychic, and physico-chemical manifestations essentially\ndistinct? Vitalists distinguish between life and thought, animists\nidentify them. In the opposite camp mechanicians, materialists, or\nmonists make the same mistake as the animists, but to that mistake they\nadd another: they assimilate the forces at play in animals and plants\nto the general forces of the universe; they confuse all three\u2014soul,\nlife, inanimate nature.\n\nThese problems belong on many sides to metaphysical speculation. They\nhave been discussed by philosophers; they have been solved from time\nimmemorial in different ways, for reasons and by arguments which it is\nnot our purpose to examine here, and which, moreover, have not changed.\nBut on some sides they belong to science, and must be tested in the\nlight of its progress. Cuvier and Bichat, for example, considered that\nthe forces in action in living beings were not only different from\nphysico-mechanical forces, but were utterly opposed to them. We now\nknow that this antagonism does not exist.\n\nThe preceding doctrines, therefore, depend up to a certain point on\nexperiment and observation. They are subject to the test of experiment\nand observation in proportion as the latter can give us information\non the degree of difference or analogy presented by psychic, vital,\nand physico-chemical facts. Now, scientific investigations have thrown\nlight on these points. There is no doubt that the analogies and the\nresemblances of these three orders of manifestations have appeared more\nand more numerous and striking as our knowledge has advanced. Hence it\nis that animism can count to-day but very few advocates in biological\nscience. Vitalism in its different forms counts more supporters, but\nthe great majority have adopted the physico-chemical theory.\n\nBoth animism and vitalism separate from matter a directing principle\nwhich guides it. At bottom they are mythological theories somewhat\nsimilar to the paganism of old. The fable of Prometheus or the story\nof Pygmalion contains all that is essential. An immaterial principle,\ndivine, stolen by the Titan from Jupiter, or obtained from Venus by\nthe Cypriot sculptor, descends from Olympus and animates the form,\ntill then inert, which has been carved in the marble or modelled in\nthe clay. In a word, there is a human statue. It receives a breath of\nheavenly fire, a vital force, a divine spark, a soul, and behold! it is\nalive. But this breath can also leave it. An accident happens, a clot\nin a vein, a grain of lead in the brain\u2014the life escapes, and all that\nis left is a corpse. A single instant has proved sufficient to destroy\nits fascination. This is how all men picture to their minds the scene\nof death. The breath escapes; something flies away, or flows away with\nthe blood. The happy genius of the Greeks conceived a graceful image\nof this, for they represented the life or the soul in the form of a\nbutterfly (Psyche) leaving the body, an ethereal butterfly, as it were,\nopening its sapphire wings.\n\nBut what is this subtle and transient guest of the human statue, this\npassing stranger which makes of the living body an inhabited house?\nAccording to the animists it is the soul itself, in the sense in which\nthe word is understood by philosophers; the immortal and reasoning\nsoul. To the vitalists it is an inferior, subordinate soul; a soul, as\nit were, of secondary majesty, the vital force, or in a word, life.\n\n_Primitive Animism._\u2014Animism is the oldest and most primitive of the\nconceptions presented to the human mind. But in so far as it is a\nco-ordinated doctrine, it is the most recent. In fact it only received\nits definitive expression in the eighteenth century, from Stahl, the\nphilosopher-physician and chemist.\n\nAccording to Tylor, one of the first speculations of primitive man, of\nthe savage, is as to the difference between the living body and the\ncorpse. The former is an inhabited house, the latter is empty. To such\nrudimentary intellects the mysterious inhabitant is a kind of _double_\nor duplicate of the human form. It is only revealed by the shadow\nwhich follows the body when illuminated by the sun, by the image of\nits reflection in the water, by the echo which repeats the voice. It\nis only seen in a dream, and the figures which people and animate our\ndreams are nothing but these doubled, impalpable beings. Some savages\nbelieve that at the moment of death the double, or the soul, takes up\nits residence in another body. Sometimes each individual possesses, not\none of these souls, but several. According to Maspero, the Egyptians\ncounted at least five, of which the principle, the _ka_ or _double_,\nwould be the aeriform or vaporous image of the living form. Space is\npeopled by souls on their travels, which leave one set of bodies to\noccupy another set. After having been the cause of life in the bodies\nwhich they animated, they react from without on other beings, and are\nthe cause of all sorts of unexpected events. They are benevolent or\nmalevolent spirits.\n\nAnalogy inevitably leads simple minds to extend the same ideas to\nanimals and plants; in a word, to attribute souls to everything alive,\nsouls more or less nomadic, wandering, or interchangeable, as is\ntaught in the doctrine of metempsychosis. Mons. L. Errera points out\nthat this primitive, co-ordinated, hierarchized doctrine\u2014meet subject\nfor the poet\u2019s art\u2014is the basis of all ancient mythologies.\n\n_The Animism of Stahl._\u2014Modern animism was much more narrow in scope.\nIt was a medical theory\u2014_i.e._ almost exclusive to man. Stahl had\nadopted it in a kind of reaction against the exaggerations of the\nmechanical school of his time. According to him, the life of the body\nis due to the intelligent and reasoning soul. It governs the corporeal\nsubstance and directs it towards an assigned end. The organs are its\ninstruments. It acts on them directly, without intermediaries. It\nmakes the heart beat, the muscles contract, the glands secrete, and\nall the organs perform their functions. Nay more, it is itself the\narchitectonic soul, which has constructed and which maintains the body\nwhich it rules. It is the _mens agitat molem_ of Virgil.\n\nIt is remarkable that these ideas, so excessively and exaggeratedly\nspiritualistic, should have been brought forward by a chemist and a\nphysician, while ideas completely opposed to these were admitted by\nphilosophers like Descartes and Leibniz, who were decided believers\nin the spirituality of the soul. Stahl had been Professor of Medicine\nat the University of Halle, physician to the Duke of Saxe-Weimar,\nand later to the King of Prussia. He left an important medical and\nchemical work, both theoretical and practical. He is the author of the\ncelebrated theory of phlogiston, which held its ground in chemistry up\nto the time of Lavoisier. He died about 1734.\n\nAnimism survived him for some time, maintained by the zeal of a few\nfaithful disciples. But after the witty mockery of Bordeu,[1] in 1742,\nit began to decay. We must, however, point out that an attempt to\nrevive this theory was made in 1878 by a well-known doctor of the last\ngeneration, E. Chauffard. While preserving the essential features of\nthe theory, this learned physician proposed to bring it into harmony\nwith modern science, and to free it from all the reproaches which had\nbeen levelled at it.\n\n [1] In a thesis presented in 1742 at Montpellier, Bordeu, then only\n twenty years of age, made game of the tasks imposed by animists on\n the Soul, \u201cwhich has to moisten the lips when required;\u201d or, \u201cwhose\n anger produces the symptoms of certain diseases;\u201d or again, \u201cwhich\n is prevented by the consequences of original sin from guiding and\n directing the body.\u201d\n\n_The Animism of E. Chauffard._\u2014These reproaches were numerous. The\nmost serious is of a philosophic nature. It rises from the difficulty\nof conceiving a direct and immediate action of the soul, considered as\na spiritual principle, upon the matter of the body. There is such an\nabyss\u2014hewn by the philosophic mind itself\u2014between soul and body, that\nit is impossible to imagine any relation between them. We can only get\na glimpse of how the soul might become an instrument of action.\n\nThis was the problem which sorely tried the genius of Leibniz.\nDescartes, in earlier days, attacked it vigorously, like an Alexander\ncutting the Gordian knot. He separated the soul from the body, and\nmade of the latter a pure machine in the government of which the soul\nhad no part. He attributed all the known manifestations of vital\nactivity to inanimate forces. Leibniz, also, was compelled to reject\nall action, all contact, all direct relation, every real bond between\nsoul and body, and to imagine between them a purely metaphysical\nrelation\u2014pre-established harmony:\u2014\u201cSoul and body agree in virtue of\nthis harmony, the harmony pre-established since the creation, and\nin no way by a mutual, actual, physical influence. Everything that\ntakes place in the soul takes place as if there were no body, and so\neverything takes place in the body as if there were no soul.\u201d At this\npoint we almost reach a scientific materialism. It is easy for the\nmaterialist to break this frail tie of pre-established harmony which so\nloosely unites body and soul, and to exhibit the organism as under the\nsole control of universal mechanics and physics.\n\nThus the weak point of Stahl\u2019s animism was the supposition of a\ndirect action exercised on the organism by a distinct, heterogeneous,\nspiritual principle.\n\nChauffard has endeavoured to avoid this pitfall. In conformity with\nmodern ideas, he has brought together what the ancient philosophers\nand Stahl himself separated\u2014the activity of matter and the activity of\nthe soul. \u201cThought, action, function, are embraced in an indissoluble\nunion.\u201d This is the classical but not very lucid theory which has been\nso often reproduced\u2014_Homo factus est anima vivens_\u2014which Bossuet has\nexpressed in the celebrated formula: \u201cSoul and body form a natural\nwhole.\u201d\n\nA second objection raised against animism is that the soul acts\nconsciously, with reflection, and with volition, and that its essential\nattributes are not found in most physiological phenomena, which, on the\ncontrary are automatic, involuntary, and unconscious. The contradictory\nnature of these characteristics has obliged vitalists to conceive of\na vital principle distinct from thought. Chauffard, agreeing here\nwith Boullieu, Tissot, and Stahl himself, does not accept this\ndistinction; he refuses to shatter the unity of the vivifying and\nthinking principle. He prefers to attribute to the soul two modes of\naction: the one which is exercised on the acts of thought, and hence\nit proceeds consciously, with reflection, and with volition; the other\nexercising control over the physiological phenomena which it governs,\n\u201cby unconscious impressions, and by instinctive determinations, obeying\nprimordial laws.\u201d This soul is hardly in keeping with his definition of\na conscious, reflecting, and voluntary principle; it is a new soul, a\nsomatic soul, singularly akin to that _rachidian soul_ which, according\nto Pfl\u00fcger, a well-known German physiologist, resides in each segment\nof the spinal marrow, and is responsible for reflex movements.\n\n_Twofold Modality of the Soul._\u2014This twofold modality of the soul, this\nduality admitted by Stahl and his disciples, was repugnant to many\nthinkers, and it is this repugnance that gave rise to the vitalistic\nschool. It appeared to them to be a heresy tainted by materialism\u2014and\nso it was. In this lay the strength and the weakness of animism. It\nadmits of a unique animating principle for all the manifestations of\nthe living being, for the higher facts in the realm of thought, and for\nthe lower facts connected with the body. It throws down the barriers\nwhich separate them. It fills up the gap between the different forms of\nhuman activity, and assimilates them the one to the other.\n\nNow this is precisely what materialism does. It, too, reduces to\na single order the psychical and physiological phenomena, between\nwhich it no longer recognizes anything but a difference of degree,\nthought being only a maximum of the vital movement, or life a minimum\nof thought. In truth, the aims of the two schools are diametrically\nopposed; the one claims to raise corporeal activity to the dignity\nof thinking activity, and to spiritualize the vital fact; the other\nlowers the former to the level of the latter and materializes the\npsychic fact. But, though the intentions are different, the result is\nidentical. Spiritualistic monism inclines towards materialistic monism.\nOne step more, and the soul, confused with life, will be confused with\nphysical forces.\n\nOn the other hand, twofold modality has this advantage, that it\nescapes the objection drawn from the existence of so many living\nbeings to which a thinking soul cannot be attributed; an anencephalous\nf\u0153tus, the young of the higher animals, the lower animals and plants,\nliving without thought, or with a minimum of real, conscious thought.\nThe advocate of animism replies that this physiological activity\nis still a soul, but one which is barely aware of its existence\u2014a\ngleam of consciousness. In this theory, the knowledge of self, the\nconsciousness, is of all degrees. On the other hand, in the eyes of the\nvitalist, it is an absolute fact which allows of no attenuation, of no\nmiddle course between the being and the non-being.\n\nIt is this conception of the continuity of the soul and life, it is\nthe affirmation of a possible lowering of the complete consciousness\ndown to a mere gleam of knowledge, and finally down to unconscious\nvital activity, which saved animism from complete shipwreck. That is\nwhy this ancient doctrine finds, even in the present day, a few rare\nsupporters. An able German scientist, G. von Bunge, well known for\nhis researches in physiological chemistry, professes animistic views\nin a work which appeared in 1889. He attributes to organized beings a\nguiding principle, a kind of vital soul. A distinguished naturalist,\nRindfleisch, of L\u00fcbeck, has likewise taken his place among the\nadvocates of what we may call neo-animism.\n\n\n\n\n CHAPTER III.\n\n VITALISM.\n\n Its Extreme Forms\u2014Early Vitalism, and Modern Neo-vitalism\u2014Advantage\n of distinguishing between Soul and Life\u2014\u00a7 1. _The Vitalism of\n Barthez_\u2014Its Extension\u2014The Seat of the Vital Principle\u2014The Vital\n Knot\u2014The Vital Tripod\u2014Decentralisation of the Vital Principle\u2014\u00a7 2.\n _The Doctrine of Vital Properties_\u2014Galen, Van Helmont, Xavier Bichat,\n and Cuvier\u2014Vital and Physical Properties antagonistic\u2014\u00a7 3. _Scientific\n Neo-vitalism_\u2014Heidenhain\u2014\u00a7 4. _Philosophical Neo-vitalism_\u2014Reinke.\n\n\n_Extreme Forms: Early Vitalism and Modern Neo-vitalism._\u2014Contemporary\nneo-vitalism has weakened primitive vitalism in some important points.\nThe latter made of the vital fact something quite specific, irreducible\neither to the phenomena of general physics or to those of thought.\nIt absolutely isolated life, separating it above from the soul, and\nbelow from inanimate matter. This sequestration is nowadays much less\nrigorous. On the psychical side the barrier remains, but it is lowered\non the material side. The neo-vitalists of to-day recognize that the\nlaws of physics and chemistry are observed within, as well as without,\nthe living body; the same natural forces intervene in both, only they\nare \u201cotherwise directed.\u201d\n\nThe vital principle of early times was a kind of anthromorphic, pagan\ndivinity. To Aristotle, this force, the _anima_, _the Psyche_, worked,\nso to speak, with human hands. According to the well-known expression,\nits situation in the human body corresponds to that of a pilot on a\nvessel, or to that of a sculptor or his assistant before the marble or\nclay. And, in fact, we have no other clear image of a cause external\nto the object. We have no other representation of a force external to\nmatter than that which is offered by the craftsman making an object, or\nin general by the human being with his activity, free, or supposed to\nbe free, and directed towards an end to be realized.\n\nPersonifications of this kind, the mythological entities, the imaginary\nbeings, the ontological fictions, which ever filled the stage in the\nmind of our predecessors, have definitely disappeared; no longer\nhave they a place in the scientific explanations of our time. The\nneo-vitalists replace them by _the idea of direction_, which is another\nform of the same idea of finality. The series of second causes in the\nliving being seems to be regulated in conformity with a plan, and\ndirected with a view to carrying it out. The tendency which exists\nin every being to carry out this plan,\u2014that is to say, the tendency\ntowards its end,\u2014gives the impulse that is necessary to carry it out.\nNeo-vitalists claim that vital force directs the phenomena which it\ndoes not produce, and which are in reality carried out by the general\nforces of physics and chemistry.\n\nThus, the directing impulse, _considered as really active_, is the last\nconcession of modern vitalism. If we go further, and if we refuse to\nthe directing idea executive power and efficient activity, the vital\nprinciple is weakened, and we abandon the doctrine. We can no longer\ninvoke it. We cease to be vitalists if the part played by the vital\nprinciple is thus far restricted. At first it was both the author of\nthe plan and the universal architect of the organic edifice; it is\nnow only the architect directing his workmen, and they are physical\nand chemical agents. It is now reduced to the plan of the work, and\neven this plan has no objective existence; it is now only an _idea_. It\nhas only a shadow of reality. To this it has been reduced by certain\nbiologists. For this we may thank Claude Bernard; and he has thereby\nplaced himself outside and beyond the weakest form of vitalism. He\ndid not consider the _idea of direction_ as a real principle. The\nconnection of phenomena, their harmony, their conformity to a plan\ngrasped by the intellect, their fitness for a purpose known to the\nintellect, are to him but a mental necessity, a metaphysical concept.\nThe plan which is carried out has only a subjective existence; the\ndirecting force has no efficient virtue, no executive power; it does\nnot emerge from the intellectual domain in which it took its rise, and\ndoes not \u201creact on the phenomena which enabled the mind to create it.\u201d\n\nIt is between these two extreme incarnations of the vital principle, on\nthe one hand an executive agent, on the other a simple directing plan,\nthat the motley procession of vitalist doctrines passes on its way.\nAt the point of departure we have a vital force, personified, acting,\nas we have stated, as if with human hands fashioning obedient matter;\nthis is the pure and primitive form of the theory. At the other extreme\nwe have a vital force which is now only a directing idea, without\nobjective existence, and without an executive r\u00f4le; a mere concept\nby which the mind gathers together and conceives of a succession of\nphysico-chemical phenomena. On this side we are brought into touch with\nmonism.\n\n_The Reasons given by the Vitalists for distinguishing Soul from\nLife._\u2014It is, in particular, on the opposite side, in the psychical\nworld, that the early vitalists professed to entrench themselves.\nWe have just seen that their doctrines were not so subtle as those\nof to-day; the vital principle to them was a real agent, and not an\nideal plan in the process of being carried out. But they distinguished\nthis spiritual principle from another co-existent with it in superior\nliving beings\u2014at any rate, in man: the thinking soul. They boldly\ndistinguished between them, because the activity of the one is\nmanifested by knowledge and volition, while on the contrary, the\nmanifestations of the other for the most part escape both consciousness\nand volition.\n\nIn fact, we know nothing of what goes on in the normal state of our\norgans. Their perfect performance of their functions is translated to\nus solely by an obscure feeling of comfort. We do not feel the beating\nof the heart, the periodic dilations of the arteries, the movements of\nthe lungs or intestine, the glands at their work of secretion, or the\nthousand reflex manifestations of our nervous system. The soul, which\nis conscious of itself, is nevertheless ignorant of all this vital\nmovement, and is therefore external to it.\n\nThis is the view of all the philosophers of antiquity. Pythagoras\ndistinguished the real soul, the thinking soul, the _Nous_, the\nintelligent and immortal principle, characterized by the attributes of\nconsciousness and volition, from the vital principle, the _Psyche_,\nwhich gives breath and animation to the body, and which is a soul of\nsecondary majesty, active, transient, and mortal. Aristotle did the\nsame. On the one side he placed the soul properly so called, the _Nous_\nor intellect\u2014that is to say, the understanding with its rational\nintelligence; on the other side was the directing principle of life,\nthe irrational and vegetative Psyche.\n\nThis distinction agrees with the fact of the diffusion of life. Life\ndoes not belong to the superior animals alone, and to the man in whom\nwe can recognize a reasoning soul. It is extended to the vast multitude\nof humbler beings to which such lofty faculties cannot be attributed,\nthe invertebrates, microscopic animals, and plants. The advantage is\ncompensated for by the inconvenience of breaking down all continuity\nbetween the soul and life; a continuity which is the principle of the\ntwo other doctrines, animism and monism, and which is, we may say, the\nvery aim and the unquestionable tendency of science.\n\nAs for classical philosophy, it satisfies the necessity of establishing\nthe unity of the living being,\u2014_i.e._, of bringing into harmony soul\nand body,\u2014but in a manner which we need not here discuss. It attributes\nto the soul several modalities, several distinct powers: powers of\nthe vegetative life, powers of the sensitive life, and powers of the\nintellectual life. And this other solution of the problem would be, in\nthe opinion of M. Gardair, in complete agreement with the doctrines of\nSt. Thomas Aquinas.\n\n\n \u00a7 1. THE VITALISM OF BARTHEZ: ITS EXTENSION.\n\n\nVitalism reached its most perfect expression in the second half\nof the eighteenth century in the hands of the representatives of\nthe Montpellier school\u2014Bordeu, Grimaud, and Barthez. The last, in\nparticular, contributed to the prevalence of the doctrine in medical\ncircles. A man of profound erudition, a collaborates with d\u2019Alembert\nin the _Encyclop\u00e6dia_, he exercised quite a preponderant influence\non the medicine of his day. Stationed at Paris during part of his\ncareer, physician to the King and the Duke of Orleans, we may say\nthat he supported his theories by every imaginable influence which\nmight contribute to their success. In consequence of this, the medical\nschools taught that vital phenomena are the immediate effects of a\nforce which has no analogues outside the living body. This conception\nreigned unchallenged up to the days of Bichat.\n\nAfter Bichat, the vitalism of Barthez, more or less modified by the\nideas of the celebrated anatomist, continued to hold its own in all the\nschools of Europe until about the middle of the nineteenth century.\nJohannes M\u00fcller, the founder of physiology in Germany, admitted, about\n1833, the existence of a unique vital force \u201caware of all the secrets\nof the forces of physics and chemistry, but continually in conflict\nwith them, as the supreme cause and regulator of all phenomena.\u201d When\ndeath came, this principle disappeared and left no trace behind. One\nof the founders of biological chemistry, Justus Liebig, who died in\n1873, shared these ideas. The celebrated botanist, Candolle, who lived\nup to 1893, taught at the beginning of his career that the vital\nforce was one of the four forces ruling in nature, the other three\nbeing\u2014attraction, affinity, and intellectual force. Flourens, in\nFrance, made the vital principle one of the five properties of forces\nresiding in the nervous system. Another contemporary, Dressel, in 1883,\nendeavoured to bring back into fashion this rather primitive, monistic,\nand efficient vitalism.\n\n_The Seat of the Vital Principle._\u2014Meanwhile, another question was\nasked with reference to this vital principle. It was a question of\nascertaining its seat: or, in other words, of finding its place in\nthe organism. Is it spread throughout the organism, or is it situated\nin some particular spot from which it acts upon every part of the\nbody? Van Helmont, a celebrated scientist at the end of the sixteenth\ncentury, who was both physician and alchemist, gave the first and\nrather quaint solution of this difficulty. The vital principle,\naccording to him, was situated in the stomach, or rather in the opening\nof the pylorus. It was the _concierge_, so to speak, of the stomach.\nThe Hebrew idea was more reasonable. The life was connected with the\nblood, and was circulated with it by means of all the veins of the\norganism. It escaped from a wound at the same time as the liquid blood.\nIt is clear that in this belief we see why the Jews were forbidden to\neat meat which had not been bled.\n\n_The Vital Knot._\u2014In 1748 a doctor named Lorry found that a very small\nwound in a certain region of the spinal marrow brought on sudden\ndeath. The position of this remarkable point was ascertained in 1812\nby Legallois, and more accurately still by Flourens in 1827. It is\nsituated in the rachidian bulb, at the level of the junction of the\nneck and the head; or more precisely, on the floor of the fourth\nventricle, near the origin of the eighth pair of cranial nerves. This\nis what was called the _vital knot_. Upon the integrity of this spot,\nwhich is no bigger than the head of a pin, depends the life of the\nanimal. Those who believed in a localisation of the vital principle\nthought that they had found the seat desired; but for that to be so the\ndestruction of this spot must be irremediable, and must necessarily\ncause death. But if the _vital knot_ be destroyed, and respiration be\nartificially induced by means of a bellows, the animal resists: it\ncontinues to live. It is only the nervous stimulating mechanism of the\nrespiratory movements which has been attacked in one of its essential\nparts.\n\nLife, therefore, resides no more in this point than it does in the\nblood or in the stomach. Later experiment has shown that it resides\neverywhere, that each organ enjoys an independent life. Each part of\nthe body is, to use Bordeu\u2019s strong expression, \u201c_an animal in an\nanimal_\u201d; or to adopt the phrase due to Bichat, \u201c_a particular machine\nwithin the general machine_.\u201d\n\n_The Vital Tripod._\u2014What then is life, or, in other words, what is the\nbiological activity of the individual, of the animal, of man? It is\nclearly the sum total, or rather, the harmony of these partial lives\nof the different organs. But in this harmony it seems that there are\ncertain instruments which dominate and sustain the others. There are\nsome whose integrity is more necessary to the preservation of existence\nand health, and of which any lesion makes death more inevitable. They\nare the lungs, the heart, and the brain. Death always ensues, said\nthe early doctors, if any one of these three organs be injured. Life\ndepends, therefore, on them, as if upon a three-legged support. Hence\nthe idea of the _vital tripod_. It is no longer a single seat for\nthe vital principle, but a kind of throne on three-supports. Life is\ndecentralized.\n\nThis was only the first step, very soon followed by many others, in the\ndirection of vital decentralization. Experiment showed, in fact, that\nevery organ separated from the body will continue to live if provided\nwith the proper conditions. And here, it is not only a question of\ninferior beings; of plants that are propagated by slips; of the _hydra_\nwhich Trembley cut into pieces, each of which generated a complete\nhydra; of the _na\u00efs_ which C. Bonnet cut up into sections, each of\nwhich reconstituted a complete annelid. There is no exception to the\nrule.\n\n_Decentralization of the Vital Principle._\u2014The result is the same in\nthe higher vertebrates, only the experiment is much more difficult. At\nthe Physiological Congress of Turin in 1901, Locke showed the heart\nof a hare, extracted from the body of the animal, and beating for\nhours as energetically and as regularly as if it were in its place.\nHe suspended it in the air of a room at the normal temperature, the\nsole condition being that it was irrigated with a liquid composed of\ncertain constituents. The animal had been dead some time. More recently\nKuliabko has shown in the same way the heart of a man still beating,\nalthough the man had been dead some eighteen hours. The same experiment\nis repeated in any physiological laboratory, in a much easier manner,\nwith the heart of a tortoise. This organ, extracted from the body,\nfitted up with rubber tubes to represent its arteries and veins, and\nfilled with the defibrinated blood of a horse or an ox taken from the\nslaughter-house, works for hours and days pumping the liquid blood into\nits rubber aorta, just as if it were pumping it into the living aorta.\n\nBut it is unnecessary to multiply examples. Every organ can be made\nto live for a longer or shorter period even though removed from its\nnatural position; muscles, nerves, glands, and even the brain itself.\nEach organ, each tissue therefore enjoys an independent existence;\nit lives and works for itself. No doubt it shares in the activity of\nthe whole, but it may be separated therefrom without being thereby\nplaced in the category of dead substances. For each aliquot part of the\norganism there is a partial life and a partial death.\n\nThis decentralization of the vital activity is finally extended in\ncomplex beings from the organs to the tissues, and from the tissues\nto the anatomical elements\u2014the cells. The idea of decentralization\nhas given birth to the second form of vitalism, a softened down and\nweakened form\u2014namely, pluri-vitalism, or the theory of vital properties.\n\n\n \u00a7 2. THE THEORY OF VITAL PROPERTIES.\n\n\nThe advocates of the theory of vital properties have cut up into\nfragments the monistic and indivisible guiding principle of Bordeu and\nBarthez. They have given it new currency\u2014pluri-vitalism. This theory\nmaintains the existence of spiritual powers of a lower order, which\ncontrol phenomena more intimately than the vital principle did. These\npowers, less lofty in their dignity than the rational soul of the\nanimists, or the soul of secondary majesty of the unitarian vitalists,\nare eventually incorporated in the living matter of which they will\nthen be no longer more than the properties. Brought into closer\nconnection therefore with the sensible world, they will be more in\nharmony with the spirit of research and with scientific progress.\n\nThe defect of the earlier conceptions, their common illusion, rose from\ntheir seeking the cause outside the object, from their demanding an\nexplanation of vital phenomena from a principle external to living,\nimmaterial, and unsubstantial matter. Here this defect is less marked.\nThe pluri-vitalists will in turn appeal to the vital properties as\nmodes of activity, inherent in the living substance in which and by\nwhich they are manifested, and derived from the arrangement of the\nmolecules of this substance\u2014that is to say, from its organization. This\nis almost the conception of the present day.\n\nBut this progress will only be realized at the end of the evolution\nof the pluri-vitalist theory. At the outset this theory seems an\nexaggeration of its predecessor, and a still more exaggerated form of\nthe mythological paganism with which it was reproached. The archeus,\nthe blas, the properties, the spirits\u2014all have at first the effect\nof the genii or of the gods imagined by the ancients to preside over\nnatural phenomena, of Neptune stirring up the waters of the sea, and\nof Eolus unchaining the winds. These divinities of the ancient world,\nthe nymphs, the dryads, and the sylvan gods, seem to be transported to\nthe Middle Ages, to that age of argument, that philosophical period of\nthe history of humanity, and there metamorphosed into occult causes,\nimmaterial powers, and personified forces.\n\n_Galen._\u2014The first of the pluri-vitalists was Galen, the physician of\nMarcus Aurelius, the celebrated author of an Encyclop\u00e6dia of which the\ngreater part has been lost, and of which the one book preserved held\nits own as the anatomical oracle and breviary throughout the Middle\nAges. According to Galen the human machine is guided by three kinds\nof spirits: _animal spirits_, presiding over the activity of the\nnervous system; _vital spirits_ governing most of the other functions;\nand finally, _natural spirits_ regulating the liver and susceptible\nof incorporation in the blood. In the sixteenth century, in the time\nof Paracelsus, Galen\u2019s spirits became _Olympic spirits_. They still\npresided over the functional activity of the organs, the liver, heart,\nand brain, but they also existed in all the bodies of nature.\n\n_Van Helmont._\u2014Finally, the theory was laid down by Van Helmont,\nphysician, chemist, experimentalist, and philosopher, endowed with\na rare and penetrating intellect. Here we find many profound truths\ncombined with fantastic dreams. Refusing to admit the direct action of\nan immaterial agent, such as the soul, on inert matter, on the body, he\nfilled up the abyss which separated them by creating a whole hierarchy\nof immaterial principles which played the part of mediators and\nexecutive agents. At the head of this hierarchy was placed the thinking\nand immortal soul; below was the sensitive and mortal soul, having for\nits minister the _principal archeus_, the _aura vitalis_, a kind of\nincorporeal agent, which is remarkably like the vital principle, and\nwhich had its seat at the orifice of the stomach. Below again were the\nsubordinate agents, the _blas_, or _vulcans_ placed in each organ, and\nintelligently directing its mechanism like skillful workmen.\n\nThese chimerical ideas are not, however, so far astray as the theory\nof vital properties. When we see a muscle contract, we say that this\nphenomenon is due to a vital property\u2014_i.e._, a property without any\nanalogue in the physical world, namely _contractility_, in the same\nway the nerve possesses two vital properties, _excitability_ and\n_conductibility_, which Vulpian proposed to blend into one, calling it\n_neurility_. These are mere names, serving as a kind of shorthand; but\nto those who believe that there is something real in it, this something\nis not very far from the _blas_ of Van Helmont. _Vulcans_, hidden in\nthe muscle or the nerve, are here detected by attraction, there by\nthe production and the propagation of the nervous influx; that is to\nsay, by phenomena of which we as yet know no analogues in the physical\nworld, but of which we cannot say that they do not exist.\n\n_X. Bichat and G. Cuvier: Vital and Physical Properties\nAntagonistic._\u2014The archeus and the blas of Van Helmont were but a\nfirst rough outline of vital properties. Xavier Bichat, the founder of\ngeneral anatomy, wearied of all these incorporeal entities, of these\nunsubstantial principles with which biology was encumbered, undertook\nto get rid of them by the methods of the physicist and the chemist. The\nphysics and the chemistry of his day referred phenomenal manifestations\nto the properties of matter, gravity, capillarity, magnetism, etc.\nBichat did the same. He referred vital manifestations to the properties\nof living tissues, if not, indeed, of living matter. Of these\nproperties as yet but very few were known: the irritability described\nby Glisson, which is the excitability of current physiology; and the\nirritability of Haller, which is nothing but muscular contractility.\nOthers had to be discovered.\n\nThere is no need to recall the mistake made by Bichat and followed\nby most scientific men of his time, such as Cuvier in France, and J.\nM\u00fcller in Germany, for the story has been told by Claude Bernard. His\nmistake was in considering the vital properties not only as distinct\nfrom physical properties but even as opposed to them. The one\npreserve the body, the others tend to destroy it. They are always in\nconflict. Life is the victory of the one; death is the triumph of the\nother. Hence the celebrated definition given by Bichat: \u201cLife is the\nsum total of functions which resist death,\u201d or the definition of the\nEncyclop\u00e6dia: \u201cLife is the contrary of death.\u201d\n\nCuvier has illustrated this conception by a graphic picture. He\nrepresents a young woman in all the health and strength of youth\nsuddenly stricken by death. The sculptural forms collapse and show the\nangularities of the bones; the eyes so lately sparkling become dull;\nthe flesh tint gives place to a livid pallor; the graceful suppleness\nof the body is now rigidity, \u201cand it will not be long before more\nhorrible changes ensue; the flesh becomes blue, green, black, one part\nflows away in putrid poison, and another part evaporates in infectious\nemanations. Finally, nothing is left but saline or earthy mineral\nprinciples, all the rest has vanished.\u201d Now, according to Cuvier, what\nhas happened?\n\nThese alterations are the effect of external agents, air, humidity, and\nheat. They have acted on the corpse just as they used to act on the\nliving being; but before death their assault had no effect, because it\nwas repelled by the vital properties. Now that life has disappeared\nthe assault is successful. We know now that external agents are not\nthe cause of these disorders. They are caused by the microbes of\nputrefaction. It is against _them_ that the organs were struggling, and\nnot against physical forces.\n\nThe mistake made by Bichat and Cuvier was inexcusable, even in their\nday. They were wrong not to attach the importance they deserved to\nLavoisier\u2019s researches. He had asserted, apropos of animal heat and\nrespiration, the identity of the action of physical agents in the\nliving body and in the external world. On the other hand, Bichat, by a\nflash of genius, decentralized life, dispersing the vital properties\nin the tissues, or, as we should now say, in the living matter. It was\nfrom the comparison between the constitution and the properties of\nliving matter and those of inanimate matter that light was to come.\n\n\n \u00a7 3. SCIENTIFIC NEO-VITALISM.\n\n\nWe can now understand the nature of modern neo-vitalism. It borrows\nfrom its predecessor its fundamental principle\u2014namely, the specificity\nof the _vital fact_. But this specificity is no longer _essential_, it\nis only _formal_. The difference between it and the physical fact grows\nless and almost vanishes. It consists of a diversity of mechanisms or\nexecutive agents. For example, digestion transforms the alimentary\nstarch in the intestines into sugar; the chemist does the same in his\nlaboratory, only he employs acids, while the organism employs special\nagents, ferments, in this case a diastase. It is a particular form of\nchemistry, but still it is a chemistry. That is how Claude Bernard\nlooked at it. The vital fact was not fundamentally distinguished from\nthe physico-chemical fact, but only in form.\n\nThis expurgated and accommodated vitalism (Claude Bernard pushed his\nconcessions so far as to call his doctrine \u201cphysico-chemical vitalism\u201d)\nwas revived a few years ago by Chr. Bohr and Heidenhain.\n\nOther biologists, instead of attributing the difference between the\nphenomena of the two orders to the manner of their occurrence, seem to\nadmit the complete identity of the mechanisms. It is no longer then in\nitself, individually, that the vital act is particularized, but in the\nmanner in which it is linked to others. The vital order is a series of\nphysico-chemical acts realizing an ideal plan.\n\nNeo-vitalism has therefore assumed two forms, one the more scientific\nand the other the more philosophical.\n\n_Chr. Bohr and Heidenhain._\u2014Its scientific form was given to it by\nChr. Bohr, an able physiologist at Copenhagen, and by Heidenhain,\na professor at Breslau, who was one of the lights of contemporary\nGerman physiology. The course of their researches led these two\nexperimentalists, working independently, to submit to fresh\ninvestigation the ideas of Lavoisier and those of Bichat, on the\nrelation of physico-chemical forces to the vital forces.\n\nIt was by no means a question of a general inquiry, deliberately\ninstituted with the object of discovering the part played respectively\nby physical and physiological factors in the performance of the various\nfunctions. Such an investigation would have taken several generations\nto complete. No; the question had only come up incidentally. Chr. Bohr\nhad studied with the utmost care the gaseous exchanges which take place\nbetween the air and the blood in the lungs. The gaseous mixture and\nthe liquid blood are face to face; they are separated by thin membrane\nformed of living cells. Will this membrane behave as an inert membrane\ndeprived of vitality, and therefore obeying the physical laws of the\ndiffusion of gases? Well! no. It does not so behave. The most careful\nmeasurements of pressures and of solubilities leave no doubt in this\nrespect. The living elements of the pulmonary membrane must therefore\nintervene in order to disturb the physical phenomenon. Things happen\nas if the exchanged gases were subjected not to a simple diffusion,\na physical fact obeying certain rules, but to a real secretion, a\nphysiological or vital phenomenon, obeying laws which are also fixed,\nbut different from the former.\n\nOn the other hand, Heidenhain was led about the same time to analogous\nconclusions with respect to the liquid exchanges which take place\nwithin the tissues, between the liquids (lymphs) which bathe the\nblood-vessels externally and the blood which those vessels contain.\nThe phenomenon is very important because it is the prologue of the\nactions of nutrition and assimilation. Here again, the two factors of\nexchange are brought into relation through a thin wall, the wall of\nthe blood-vessel. The physical laws of diffusion, of osmosis, and of\ndialysis, enable us to foretell what would take place if the vitality\nof the elements of the wall did not intervene. Heidenhain thought he\nobserved that things took place otherwise. The passage of the liquids\nis disturbed by the fact that the cellular elements are alive. It\nassumes the characteristics of a physiological act, and no longer\nthose of a physical act. Let us add that the interpretation of these\nexperiments is difficult, and it has given rise to controversies which\nstill persist.\n\nThese two examples, around which others might be grouped, have led\ncertain physiologists to diminish the importance of the physical\nfactors in the functional activity of the living being to the advantage\nof the physiological factors. It would therefore seem that the vital\nforce, to use a rather questionable form of language, withdraws in\na certain measure the organized being from the realm of physical\nforces\u2014and this conclusion is one form of contemporary neo-vitalism.\n\n\n \u00a7 4. PHILOSOPHICAL NEO-VITALISM.\n\n\nContemporary neo-vitalism has assumed another form, more philosophical\nthan scientific, by which it is brought closer to vitalism, properly\nso called. We should like to mention the experiment of Reinke,[2] in\nGermany. Reinke is a botanist of distinction, who distinguishes the\nspeculative from the positive domain of science, and cultivates both\nwith success.\n\n [2] Reinke, _Die Welt als That_; Berlin, 1899.\n\nHis ideas are analogous to those of A. Gautier, of Chevreul, and of\nClaude Bernard himself. He thinks, with these masters, that the mystery\nof life is not to be found in the nature of the forces that it brings\ninto play, but in the direction that it gives them. All these thinkers\nare struck by the order and the direction impressed upon the phenomena\nwhich take place in the living being, by their interconnection, by\ntheir apparent adaptation to an end, by the kind of impression that\nthey give of a plan which is being carried out. All these reflections\nlead Reinke to attach great weight to the idea of a \u201cdirecting force.\u201d\n\nThe physico-chemical energies are no doubt the only ones which are\nmanifested in the organized being, but they are directed as a blind man\nis by his guide. It seems as if a _double_ accompanies them like a\nshadow. This intelligent guide of blind, material force is what Reinke\ncalls a _dominant_. Nothing could be more like the blas and the archeus\nof Van Helmont. Material energies would thus be paired off with their\nblas, their dominants, in the living organisms. In them there would\ntherefore be two categories of force: \u201cmaterial forces,\u201d or rather,\nmaterial energies obeying the laws of universal energetics; and in the\nsecond place, intelligent \u201cspiritual forces,\u201d the dominants. When the\nsculptor is working his marble, in every blow which elicits a spark\nthere is something more than the strong force of the hammer. There is\nthought, the volition of the artist, which is realizing a plan. In a\nmachine there is more than machinery. Behind the wheels is the object\nwhich the author had in view when he adjusted them for a determined\nend. The energies spent in action are regulated by the adjustment\u2014that\nis to say, by the dominants due to the intellect of the constructor.\n\nThus it is in the living machine. The dominants in this case are the\nguardians of the plan, the agents of the aim in view. Some regulate\nthe functional activity of the living body, and some regulate its\ndevelopment and its construction. Such is the second form, the\nphilosophical form, extreme and teleological, of contemporary\nneo-vitalism.\n\n\n\n\n CHAPTER IV.\n\n THE MONISTIC THEORY.\n\n Physico-chemical Theory of Life.\u2014Iatro-mechanism.\u2014Descartes,\n Borelli.\u2014Iatro-chemistry.\u2014Sylvius le Bo\u00eb.\u2014The Physico-chemical Theory\n of Life.\u2014Matter and Energy.\u2014Heterogeneity is merely the result of the\n arrangement or combination of homogeneous bodies.\u2014Reservation relative\n to the world of thought.\u2014The Kinetic Theory.\n\n\nThe unicist or monistic doctrine gives us a third way of conceiving\nthe functional activity of the living being, by levelling and\nblending its three forms of activity\u2014spiritual, vital, and material.\nIt was expressed in the seventeenth and eighteenth centuries in\n\u201ciatro-mechanism\u201d and \u201ciatro-chemistry,\u201d conceptions to which have more\nrecently succeeded the physico-chemical doctrine of life, and finally\n\u201ccurrent materialism.\u201d\n\nMaterialism is not only a biological interpretation; it is a universal\ninterpretation applicable to the whole of nature, because it is\nbased on a determinate conception of matter. Here we find ourselves\nconfronted by the eternal enigma discussed by philosophers relative\nto this fundamental problem of force and matter. We know what\nanswers were given to the problem by the Ionic philosophers\u2014Thales,\nDemocritus, Heraclitus, and Anaxagoras, who discarded the agency of\nevery spiritual power external to matter. The explanation of the\nworld, the explanation of life, were reduced to the play of physical\nor mechanical forces. Epicurus, a little later, maintained that the\nknowledge of matter and its different forms accounts for all phenomena,\nand therefore for those of life.\n\nDescartes, sharply separating the metaphysical world\u2014that is to say,\nthe soul defined by its attribute, thought\u2014from the physical or\nmaterial world characterized by extension, practically came to the same\nconclusions as the materialists of antiquity. To him, as to them, the\nliving body was a mere machine.\n\n_Iatro-mechanism. Descartes. Borelli._\u2014This, then, is the theory of the\niatro-mechanicians, of which we may consider Descartes the founder,\ninstead of the Greek philosophers. These ideas held their own for two\ncenturies, and were productive of such fruitful results in the hands of\nBorelli, Pitcairn, Hales, Bernoulli, and Boerhaave, as to justify the\njest of Bacon that \u201cthe philosophy of Epicurus had done less harm to\nscience than that of Plato.\u201d The iatro-mechanic school tenaciously held\nits own until Bichat came upon the scene.\n\n_Iatro-chemistry. Sylvius le Bo\u00eb._\u2014It was from a reaction against their\nexaggerations that Stahl created animism, and the Montpellier school\ncreated vitalism. We gather some idea of the extravagant character\nof their explanations by reading Boerhaave. To this celebrated\ndoctor the muscles were springs, the heart was a pump, the kidneys\na sieve, and the secretions of the glandular juices were produced\nby pressure; the heat of the body was the result of the friction of\nthe globules of blood against the walls of the blood-vessels; it was\ngreater in the lungs because the vessels of the lungs were supposed\nto be narrower than those of other organs. The inadequacy of these\nexplanations suggested the idea of completing them by the aid of\nthe chemistry which was then springing into being. This chemistry,\nrudimentary as it was, longed for a share in the government of living\nbodies and in the explanation of their phenomena. Distillations,\nfermentations, and effervescences are now seen to play their r\u00f4le, a\nr\u00f4le which was premature and carried to excess. Iatro-chemistry from\nthe general point of view is only an aspect of iatro-mechanics; but it\nis also an auxiliary. Sylvius le Bo\u00eb and Willis were its most eminent\nrepresentatives. This theory remained in the background until chemistry\nmade its great advance\u2014that is to say, in the days of Lavoisier. After\nthat, its importance has gradually increased, particularly in the\npresent day. Nowadays, the general tendency is to regard the organic\nfunctional activity, or even morphogeny\u2014_i.e._, whatever there is\nthat is most peculiar to and characteristic of living beings\u2014as a\nconsequence of the chemical composition of their substance. This is a\npoint of capital importance, and to it we must recur.\n\n_The Physico-chemical Theory of Life._\u2014Contemporary biological schools\nhave made many efforts to secure themselves from any slips on the\nphilosophical side. They have avoided in most cases the psychological\nproblem; they have deliberately refrained from penetrating into the\nworld of the soul. Hence, _the physico-chemical theory_ of life has\nbeen built up free from spiritualistic difficulties and objections.\nBut this prudence did not exclude the tendency. And there is no doubt,\nas Armand Gautier said, that \u201creal science can affirm nothing, but\nit also can deny nothing outside observable facts;\u201d and again, that\n\u201conly a science progressing backwards can venture to assert that matter\nalone exists, and that its laws alone govern the world.\u201d It is none the\nless true that by establishing the continuity between inert matter and\nliving matter, we thereby render probable the continuity between the\nworld of life and the world of thought.\n\n_Matter and Energy._\u2014Besides, and without any wish to enter into\nthis burning controversy, it is only too evident that there is no\nagreement as to the terms that are used, and in particular as to\n\u201cmatter\u201d and \u201claws of matter.\u201d It is not necessary to repeat that the\ngeometrical mould in which Descartes cast his philosophy has long\nsince been broken. The celebrated philosopher, in defining matter by\none attribute\u2014extension, does not enable us to grasp its activity, an\nactivity revealed by all natural facts; and in defining the soul by\nthought alone, prevents us from seeking in it the principle of this\nmaterial activity. This purely passive matter, consisting of extension\nalone, this _bare matter_ was to Leibniz a pure concept. A philosopher\nof our own time, M. Magy, has called it a sensorial illusion. The\nbodies of nature exhibit to us _matter clad_ with energy, formed by\nthe indissoluble union of extension with an inseparable dynamical\nprinciple. The Stoics declared that matter is mobile and not immobile,\nactive and not inert. Leibniz also had this in his mind when he\nassociated it indissolubly with an active principle, an \u201centelechy.\u201d\nOthers have said that matter is \u201can assemblage of forces,\u201d or with P.\nBoscovitch, \u201ca system of indivisible points without extension, centres\nof force, in fact.\u201d Space would be the geometrical locus of these\npoints.\n\nIn this conception the materialistic school finds the explanation of\nall phenomenality. Physical properties, vital phenomena, psychical\nfacts, all have their foundation in this immanent activity. Material\nactivity is a minimum of soul or thought which, by continuous gradation\nand progressive complexity, without solution of continuity, without\nan abrupt transition from the homogeneous to the heterogeneous, rises\nthrough the series of living beings to the dignity of the human soul.\nThe observation of the transitions, an imperfect tracing of the\ngeometrical method of limits, thus enables us to pass from material to\nvital, and from thence to psychical activity.\n\n_Apparent Heterogeneity is the Result of the Arrangement or the\nCombination of Homogeneous Bodies._\u2014In this system, material energy,\nlife, soul would only be more and more complex combinations of the\nconsubstantial activity with material atoms. Life appears distinct from\nphysical force, and thought from life, because the analysis has not yet\nadvanced far enough. Thus, glass would appear to the ancient Chaldeans\ndistinct from the sand and salt of which they made it. In the same way,\nagain, water, to modern eyes, is distinct from its constituents, oxygen\nand hydrogen. The whole difficulty is that of explaining what this\n\u201carrangement\u201d of the elements can introduce that is new in the aspect\nof the compound. We must know what novelty and apparent homogeneity\nthe variety of the combinations, which are only special arrangements\nof the elementary parts, may produce in the phenomena. But we do\nnot know, and it is this ignorance which leads us to consider them\nas heterogeneous, irreducible, and distinct in principle. The vital\nphenomenon, the complexus of physico-chemical facts, thus appears to us\nessentially different from those facts, and that is why we picture to\nourselves \u201cdominants\u201d and \u201cdirecting forces\u201d more or less analogous to\nthe sidereal guiding principle of Kepler, which, before the discovery\nof universal attraction, regulated the harmony of the movements of the\nplanets.\n\n_A Reservation relative to the Psychical Order._\u2014The scientific mind\nhas shown in every age a real predilection towards the mechanical or\nmaterialistic theory. Contemporary scientists as a whole have accepted\nit in so far as it blends the vital and the physical orders. Objections\nand contradictions are only offered in the realm of psychology. A.\nGautier, for example, has contested with infinite originality and\nvigour the claims of the materialists who would reduce the phenomenon\nof thought to a material phenomenon. The most general characteristic\nof material phenomenality is\u2014as we shall later see\u2014that it may be\nconsidered as a mutation of energy\u2014_i.e._, it obeys the laws of\nenergetics. Now thought, says A. Gautier, is not a form of material\nenergy. Thought, comparison, volition, are not acts of material\nphenomenality; they are states. They are realities; they have no\nmass; they have no physical existence. They respond to adjustments,\narrangements, and concerted groupings of material manifestations of\nchemical molecules. They escape the laws of energetics.\n\n_Kinetic Theory._\u2014We shall lay aside for a moment this serious problem\nrelative to the limits of the world of conscious thought and of the\nworld of life. It is on the other side, on the frontiers of living and\ninanimate nature, that the mechanical view triumphs. It has furnished a\nuniversal conception agreeing with phenomena of every kind\u2014viz., the\nkinetic theory, which ascribes everything in nature to the movements of\nparticles, molecules, or atoms.\n\nThe living and the physical orders are here reduced to one unique\norder, because all the phenomena of the sensible universe are\nthemselves reduced to one and the same mechanics, and are represented\nby means of the atom and of motion. This conception of the world,\nwhich was that of the philosophers of the Ionic school in the remotest\nantiquity, which was modified later by Descartes and Leibniz, has\npassed into modern science under the name of the kinetic theory. The\nmechanics of atoms ponderable or imponderable, would contain the\nexplanation of all phenomenality. If it were a question of physical\nproperties or vital manifestations, the objective world in final\nanalysis would offer us nothing but motion. Every phenomenon would be\nexpressed by an atomistic integral, and that is the inner reason of\nthe majestic unity which reigns in modern physics. The forces which\nare brought into play by Life are no longer to be distinguished in\nthis ultimate analysis from other natural forces. All are blended in\nmolecular mechanics.\n\nThe philosophical value of this theory is undeniable. It has exercised\non physical science an influence which is justified by the discoveries\nwhich it has suggested. But to biology, on the other hand, it has lent\nno aid. It is precisely because it descends too deeply into things, and\nanalyzes them to the uttermost, that it ceases to throw any light upon\nthem. The distance between the hypothetical atom and the apparent and\nconcrete fact is too great for the one to be able to throw light on the\nother. The vital phenomenon vanishes with its individual aspect; its\nfeatures can no longer be distinguished.\n\nBesides, a whole school of contemporary physicists (Ostwald of Leipzig,\nMach of Vienna) is beginning to cast some doubt on the utility of the\nkinetic hypothesis in the future of physics itself, and is inclined to\npropose to substitute for it the theory of energetics. We shall see,\nin every case, that this other conception, as universal as the kinetic\ntheory, _the theory of Energy_, causes a vivid light to penetrate into\nthe depths of the most difficult problems in physiology.\n\nSuch are, with their successive transformations, the three principal\ntheories, the three great currents between which biology has been\ntossed to and fro. They are sufficiently indicative of the state of\npositive science in each age, but one is astonished that they are not\nmore so; and this is due to the fact that these conceptions are too\ngeneral. They soar too high above reality. More characteristic in this\nrespect will be particular theories of the principal manifestations of\nliving matter, of its perpetuity by generation, of the development by\nwhich it acquires its individual form, on heredity. It is here that it\nis of importance to grasp the progressive march of science\u2014that is to\nsay, the design and the plan of the building which is being erected,\n\u201cblindly, so to speak,\u201d by the efforts of an army of workers, an army\nbecoming more numerous day by day.\n\n\n\n\n CHAPTER V.\n\nTHE EMANCIPATION OF SCIENTIFIC RESEARCH FROM THE YOKE OF PHILOSOPHICAL\n THEORIES.\n\n The excessive use of Hypothetical Agents in Physiological\n Explanations\u2014\u00a7 1. _Vital Phenomena in Fully-constituted\n Organisms_\u2014Provisory Exclusion of the Morphogenic idea\u2014The Realm\n of the Morphogenic Idea as the Sanctuary of Vital Force\u2014\u00a7 2. _The\n Physiological Domain properly so called_\u2014Harmony and Connection\n of Phenomena\u2014Directive Forces\u2014Claude Bernard\u2019s Work\u2014Exclusion\n of Vital Force, of Final Cause, of the \u201cCaprice\u201d of Living\n Nature\u2014Determinism\u2014The Comparative Method\u2014Generality of Vital\n Phenomena\u2014Views of Pasteur.\n\n\nThe theories whose history we have just sketched in broad outline long\ndominated science and exercised their influence on its progress.\n\nThis domination has ceased to exist. Physiology has emancipated itself\nfrom their sway, and this, perhaps, is the most important revolution\nin the whole history of biology. Animism, vitalism, materialism,\nhave ceased to exercise their tyranny on scientific research. These\nconceptions have passed from the laboratory to the study; from being\nphysiological, they have become philosophical.\n\nThis result is the work of the physiologists of sixty years ago. It\nis also the consequence of the general march of science and of the\nprogress of the scientific spirit, which shows a more and more marked\ntendency to separate completely the domain of facts from the domain of\nhypotheses.\n\n_Excessive Use of Hypothetical Agents in Physiological\nExplanations._\u2014It may be said that in the early part of the nineteenth\ncentury, in spite of the efforts of a few real experimenters from\nHarvey to Spallanzani, Hales, Laplace, Lavoisier, and Magendie, the\nscience of the phenomena of life had not followed the progress of\nthe other natural sciences. It remained in the fog of scholasticism.\nHypotheses were mingled with facts, and imaginary agents carried out\nreal acts, in inexpressible confusion. The soul (_animism_), the vital\nforce (_vitalism_), and the final cause (_finalism_, _teleology_)\nserved to explain everything.\n\nIn truth, it was also at this time that physical agents, electric and\nmagnetic fluids, or, again, chemical affinity, played an analogous\npart in the science of inanimate nature. But there was at least this\ndifference in favour of physicists and chemists, that when they had\nattributed some new property or aptitude to their hypothetical agents\nthey respected what they attributed. The physiological physicians\nrespected no law, they were subject to no restraint. Their vital force\nwas capricious; its spontaneity made anticipation impossible; it acted\narbitrarily in the healthy body; it acted more arbitrarily still in the\ndiseased body. All the subtlety of medical genius was called into play\nto divine the fantastic behaviour of the spirit of disease. If we speak\nhere of physiologists and doctors alone and do not quote biologists, it\nis because the latter had not yet made their appearance as authorities;\ntheir science had remained purely descriptive, and they had not yet\nbegun to explain phenomena.\n\nSuch was the state of things during the first years of the nineteenth\ncentury. It lasted, thanks to the founders of contemporary\nphysiology\u2014Claude Bernard in France, and Br\u00fccke, Dubois-Reymond,\nHelmholtz, and Ludwig in Germany\u2014until a separation took place between\nbiological research and philosophical theories. This delimitation\noperated in physiology properly so called\u2014_i.e._ in a branch of the\nbiological domain in which as yet joint tenancy had been the rule. An\nimportant revolution fixed the respective divisions of experimental\nscience and philosophical interpretation. It was understood that the\none ends where the other begins, that the one follows the other,\nthat one may not cross the other\u2019s path. There is between them only\none doubtful region about which there is dispute, and this uncertain\nfrontier is constantly being shifted and science daily gains what\nphilosophy loses.\n\n\n \u00a7 1. VITAL PHENOMENA IN CONSTITUTED ORGANISMS.\n\n\nA displacement of this kind had taken place at the time of which we\nspeak. It was agreed, that as far as concerns the phenomena which take\nplace in _a constructed and constituted living organism_, it would\nno longer be permissible to allow to intervene in their explanation\nforces or energies other than those which are brought into play in\ninanimate nature. Just as when explaining the working of a clock, the\nphysicist will not invoke the volition or the art of the maker, or\nthe design that he had in view, but only the connection of causes and\neffects which he has utilized; so, for the living machine, whether\nthe most complex, such as the human body, or the most elementary,\nsuch as the cell, we may not invoke a final cause, a vital force,\nexternal to that organism and acting on it from without, but only the\nconnections and the fluctuations of effects which are the sole actual\nand efficient causes. In other words Ludwig, and Claude Bernard in\nparticular, expelled from the domain of active phenomenality the three\nchimeras\u2014Vital Force, Final Cause, and the \u201cCaprice\u201d of Living Nature.\n\nBut the living being is not only a _completely constructed and\ncompletely constituted_ organism. It is not a finished clock. It is a\nclock which is making itself, a mechanism which is constructing and\nperpetuating itself. Nothing of the kind is known to us in inanimate\nnature. Physiology has found\u2014in what is called morphogeny\u2014its temporary\nlimit. It is beyond this limit, it is in the study of phenomena by\nwhich the organism is constructed and perpetuated, it is in the region\nof the functions of generation and development, that philosophical\ndoctrines expand and flourish. This is the present frontier of these\ntwo powers, philosophy and science. We shall presently delimit them\nmore precisely. W. K\u00fchne, a well-known scientist whose death is\ndeplored, not in Germany alone, amused himself by studying the division\nof biological doctrines among the members of learned societies and in\nthe world of academies. He summed up this kind of statistical inquiry\nby saying in 1898 at the Cambridge Congress, that physiologists were\nnearly all advocates of the physico-chemical doctrine of life, and that\nthe majority of naturalists were advocates of vital force, and of the\ntheory of final causes.\n\n_Domain of the Morphogenic Idea as the Last Sanctuary of Vital\nForce._\u2014We see the reason for this. Physiology, in fact, has taken\nup its position in the explanation of the functional activity of\nthe constituted organism\u2014_i.e._, on a ground where intervene, as we\nshall show further on, no energies and no matter other than universal\nenergies and matter. Naturalists, on the other hand, have more\nespecially considered\u2014and from the descriptive point of view alone,\nat least up to the times of Lamarck and Darwin\u2014the functions, the\ngeneration, the development and the evolution of species. Now these\nfunctions are most refractory and inaccessible to physico-chemical\nexplanations. So, when the time came to give an account of what they\nhad done, the zoologists had substituted for executive agents nothing\nbut vital force under its different names. To Aristotle it is the vital\nforce itself which, as soon as it is introduced into the body of the\nchild, moulds its flesh and fashions it in the human form. Contemporary\nnaturalists, the Americans C. O. Whitman and C. Philpotts, for example,\ntake the same line of argument. Others, such as Blumenbach and Needham,\nin the eighteenth century, invoked the same division under another\nname, that of the _nisus formativus_. Finally, others play with words;\nthey talk of heredity, of adaptation, of atavism, as if these were\nreal, active, and efficient beings; while they are only appellations,\nnames applied to collections of facts.\n\nThis region was therefore eminently favourable to the rapid increase of\nhypotheses, and so they abounded. There were the theories of Buffon,\nof Lamarck, of Darwin, of Herbert Spencer, of E. Haeckel, of His, of\nWeismann, of De Vries, and of W. Roux. Each biologist of any mark\nhad his own, and the list is endless. But here already this domain of\ntheoretical speculation is checked on various sides by experiment.\nJ. Loeb, a pure physiologist, has recently given his researches a\ndirection in which zoology believes may be found the explanation of\nthe mysterious part played by the male element in fecundation. On\nthe other hand, the first experiment of the artificial division of\nthe living cell (_merotomy_), with its light upon the part played by\nthe nucleus in the preservation and regeneration of the living form,\nis also the work of a physiological experimenter. It dates back to\n1852, and is due to Augustus Waller. This experiment was made on the\nsensitive nervous cell of the spinal ganglions and on the motor cell\nof the anterior cornua of the spinal cord. The effects were correctly\ninterpreted twelve or fifteen years later. All that zoologists have\ndone is to repeat, perhaps unconsciously, this celebrated experiment\nand to confirm the result.\n\nThus we see that the attack upon the vitalist sanctuary has commenced.\nBut it would be a grave mistake to suppose that final cause and vital\nforce are on the point of being dislodged from their entrenchments.\nPhilosophical speculation has an ample field before it. Its frontiers\nmay recede. For a long time yet there will be room for a more or less\nmodernized vitalism.\n\n\n \u00a7 2. THE PHYSIOLOGICAL DOMAIN PROPERLY SO CALLED.\n\n\nVitalism is even found installed in the region of physiology, although\nfor the moment this science limits its ambition to the consideration\nof the completely constructed organized being, perfected in its form.\nThe explanation of the working of this constituted machine cannot be\ncomplete until we take into account the harmony and the adjustment of\nits parts.\n\n_Harmony and Connection of Parts: Directive Forces._\u2014These constituent\nparts are the cells. We know that the progress of anatomy has resulted\nin the cellular doctrine\u2014_i.e._, in the two-fold affirmation that the\nmost complicated organism is composed of microscopic elements, the\ncells, all similar, true stones of the living building, and that it\nderives its origin from a single cell, egg, or spore, the sexual cell,\nor cell of germination. The phenomena of life, looked at from the point\nof view of the formed individual, are therefore harmonized in space;\njust as, regarded from the point of view of the individual in formation\nand in the species, they are connected in time. This harmony and this\nconnection are in the eyes of the majority of men of science the most\ncharacteristic properties of the living being. This is the domain of\n_vital specificity_, of the _directive forces_ of Claude Bernard and A.\nGautier, and of the _dominants_ of Reinke. It is not certain, however,\nthat this order of facts is more specific than the other. Generation\nand development have been considered by many physiologists, and quite\nrecently by Le Dantec, as simple aspects or modalities of nutrition or\nassimilation, the common and fundamental property of every living cell.\n\n_The Work of Claude Bernard. Exclusion of Vital Force, of Vital Cause,\nof the \u201cCaprice\u201d of Living Nature._\u2014It is not, however, a slight\nadvance or inconsiderable advantage to have eliminated vitalistic\nhypotheses from almost the whole domain of present-day physiology, and\nto have them, as it were, thrown back into its hinterland. This is the\nwork of the scientific men of the first half of the nineteenth century,\nand particularly of Claude Bernard, who has thereby won the name of\nthe founder or lawgiver of physiology. They found in the old medical\nschool an obstinate adversary glorying in its sterile traditions. In\nvain was it proved that vital force cannot be an efficient cause; that\nit was a creation of the brain, an insubstantial phantom introduced\ninto the anatomical marionette and moving it by strings at the will of\nany one\u2014its adepts having only to confer upon it a new kind of activity\nto account for the new act. All that had been shown with the utmost\nclearness by Bonnet of Geneva, and by many others. It had also been\nsaid that the teleological explanation is equally futile, since it\nassigns to the present, which exists, an inaccessible, and evidently\nultimately inadequate cause, which does not yet exist. These objections\nwere in vain.\n\n_Determinism._\u2014And so it was not by theoretical arguments that the\ncelebrated physiologist dealt with his adversaries, but by a kind of\nlesson on things. In fact he was continually showing by examples that\nvitalism and the theory of final causes were idle errors which led\nastray experimental investigation; that they had prevented the progress\nof research and the discovery of the truth in every case and on every\npoint in which they had been invoked. He laid down the principle of\n_biological determinism_, which is nothing but the negation of the\n\u201ccaprice\u201d of living nature. This postulate, so evident that there was\nno need to enunciate it in the physical sciences, had to be shouted\nfrom the housetops for the benefit of supporters of vital spontaneity.\nIt is the statement that, under determined circumstances materially\nidentical, the same vital phenomena will be identically reproduced.\n\n_Comparative Method._\u2014Claude Bernard completed this critical work by\nlaying down the laws of experiment on living beings. He commended as\nthe rational method of research the _comparative method_. This should\nbe, and is in fact, the daily instrument of all those who work in\nphysiology. It compels the investigator in every research bearing\non organized beings to institute a series of tests, such that the\nconditions which are unknown and impossible to know may be regarded\nas identical from one test to another; and when we are certain that a\nsingle condition is variable, it compels him to discover the character\nof the condition we are dealing with, and to learn to appreciate, and\nto measure its influence. It is safe to say that the errors which are\ndaily committed in biological work have their cause in some infraction\nof this golden rule. In physical science the obligation to follow\nthe comparative method is much less felt. In most cases the _witness\ntest_[3] is useless. In physiology the witness test is indispensable.\n\n [3] In an article on the experimental method recently published in the\n _Dictionnaire de Physiologie_, M. Ch. Richet writes as follows:\u2014\u201cWe\n must therefore never cease to carry out comparative experiments.\n I do not hesitate to say that this comparison is the basis of the\n experimental method.\u201d It is in fact what was taught by Claude\n Bernard in maxim and by example. It is no exaggeration to assert\n that nine-tenths of the errors which take place in research work\n are imputable to some breach of this method. When an investigator\n makes a mistake, save in the case of material error, it is almost\n certainly due to the fact that he has neglected to carry out one\n of the comparative tests required in the problem before him. The\n following is an instance which happened since the above pages were\n written:\u2014Several years ago a chemist announced the existence in the\n blood serum of a ferment, lipase, capable of saponifying fats\u2014that is\n to say, of extracting from them the fatty acid. From this he deduced\n many consequences relative to the mechanism of fermentations. But on\n the other hand, it has been since shown (April 1902) that this lipase\n of the serum does not exist. How did the error arise? The author in\n question had mixed normally obtained serum with oil, and he had noted\n the acidification of the mixture; he assured himself of the fact by\n adding carbonate of soda. He saw the alkalinity of the mixture, serum\n + oil + carbonate of soda, diminish, and he drew the conclusion that\n the acid came from the saponified oil. He did not make the comparative\n test, serum + carbonate of soda. If he had done so, he would have\n ascertained that it also succeeded, and that therefore as the acid did\n not come from the saponification of the oil, since there was none, its\n production could not prove the existence of a lipase.\n\n_Generality of Vital Phenomena._\u2014If we add that Claude Bernard opposed\nthe narrow opinion, so dear to early medicine, which limited the\nconsideration of vitality to man, and the contrary notion of the\nessential generality of the phenomena of life from man to the animal,\nand from the animal to the plant, we shall have given very briefly an\nidea of the kind of revolution which was accomplished about the year\n1864, the date of the appearance of the celebrated _l\u2019Introduction \u00e0 la\nm\u00e9decine exp\u00e9rimentale_.\n\nThe ideas we have just recalled seem to be as evident as they are\nsimple. These principles appear so well founded that in a measure they\nform an integral part of contemporary mentality. What scientist would\nnowadays deliberately venture to explain some biological fact by the\nintervention of the evidently inadequate vital force or final cause?\nAnd who, to account for the apparent inconsistency of the result,\nwould bring forward the \u201ccaprice\u201d of living nature? And who again would\nopenly dispute the utility of the comparative method?\n\nWhat the physiologists of to-day, according to Claude Bernard, would no\nlonger do, their predecessors would do, and not the least important of\nthem. Longet, for example, at a full meeting of the Acad\u00e9mie, apropos\nof recurrent sensibility, and Colin (of Alfort), communicating his\nstatistical results on the temperature of two hearts, accepted more or\nless explicitly the indetermination of vital facts. And why confine\nour remarks to our predecessors? The scientists of to-day are much\nthe same. So here again we see the reappearance of the phantom of the\nfinal cause in so-called scientific explanations. One fact is accounted\nfor by the necessity of the self-defence of the organism; another by\nthe necessity to a warm-blooded animal of keeping its temperature\nconstant. Le Dantec has recently reproached zoologists for giving as\nan explanation of fecundation the advantage that an animal enjoys in\nhaving a double line of ancestors. We might as well say, as L. Errera\nhas pointed out, that the inundations of the Nile occur in order to\nbring fertility to Egypt.\n\nWe must not therefore depreciate the marvellous work which has\nemancipated modern physiology from the tutelage of early theories.\nThe witnesses of this revolution appreciated its importance. One of\nthem remarked as follows, on the appearance of _l\u2019Introduction \u00e0 la\nm\u00e9decine exp\u00e9rimentale_, which contained, however, only a portion of\nthe theory:\u2014\u201cNothing more luminous, more complete, or more profound,\nhas ever been written upon the true principles of an art so difficult\nas that of experiment. This book is scarcely known because it is on a\nlevel to which few people nowadays attain. The influence it will have\non medical science, on its progress, and on its very language, will\nbe enormous. I cannot now prove my assertion, but the reading of this\nbook will leave so strong an impression that I cannot help thinking\nthat a new spirit will at once inspire these splendid researches.\u201d\nThis was said by Pasteur in 1866. That is what he thought of the work\nof his senior and his rival, at the moment when he himself was about\nto inspire those \u201csplendid researches\u201d with the movement of reform,\nthe importance and the consequences of which have no equivalent in\nthe history of science. By their discoveries and their teaching, by\ntheir examples and their principles, Claude Bernard and Pasteur have\nsucceeded in emancipating a portion of the domain of vital facts from\nthe direct intervention of hypothetical agents and first causes. They\nwere compelled, however, to leave to philosophical speculation, to\ndirecting forces, to animism, to vitalism, an immense provisory field,\nthe field which corresponds to the functions of generation and of\ndevelopment, to the life of the species and to its variations. Here we\nfind them again in various disguises.\n\n\n\n\n BOOK II.\n\n THE DOCTRINE OF ENERGY AND THE LIVING WORLD.\n\n Summary: General Ideas of Life.\u2014Elementary Life.\u2014Chapter I. Energy\n in General.\u2014Chapter II. Energy in Biology.\u2014Chapter III. Alimentary\n Energetics.\n\n\n GENERAL IDEAS OF LIFE. ELEMENTARY LIFE.\n\n\n_Life is the Sum-total of the Phenomena Common to all Living Beings.\nElementary Life._\u2014Living beings differ more in form and configuration\nthan in their manner of being. They are distinguished more by their\nanatomy than by their physiology. There are, in fact, phenomena common\nto all, from the highest to the lowest. This is because there is that\nsimilar or identical foundation, that _quid commune_ which has enabled\nus to apply to them the common name of \u201cliving beings.\u201d Claude Bernard\ngave to this sum-total of manifestations common to all (nutrition,\nreproduction) the name of _elementary life_. To him _general\nphysiology_ was _the study of elementary life_; the two expressions\nwere equivalent, and they were equivalent to a longer formula which\nthe illustrious biologist has given as a title to one of his most\ncelebrated works\u2014_The Study of the Phenomena Common to all Living\nBeings, Animals, and Plants_. From this point of view each being is\ndistinguished from another being as a given _individual_ and as a\nparticular _species_; but all are in some way alike and thus resemble\none another: common life, elementary life, the essential phenomena of\nlife; it is _life itself_.[4]\n\n [4] Le Dantec has objected to this conception of phenomena common to\n different living beings. He insists that all phenomena which take\n place in a given living being are proper to him, and differ, however\n slightly, from those of another individual. The objection is more\n specious than real.\n\nThe manifestations of life may therefore be regarded from the point\nof view of what is most general among them. As we go down the scale\nof anatomical organization, as we pass from apparatus (circulatory,\ndigestive, respiratory, nervous) to the _organs_ which compose them,\nfrom the organs to the _tissues_, and finally from the tissues to the\n_anatomical elements_ or _cells_ of which they are formed, we approach\nthat common, physiological dynamism which is _elementary life_, but we\ndo not actually reach it. The cell, the anatomical element, is still a\ncomplicated structure. The elementary fact is further from us and lower\ndown. It is in the living matter, in the molecule of this matter, and\nthere we must seek it.\n\nGalen gave in days gone by as the object of researches on life, the\nknowledge of the use of the different organs of the animal machine;\n\u201cde usu partium.\u201d Later, Bichat assigned to them as their end the\ndetermination of the _properties of tissues_. Modern anatomists and\nzoologists try to reach the constituent element of these tissue\u2014the\ncell. Their dream is to construct a _cellular physiology_, a\n_physiological cytology_; but we must go further than that.\n\n_General Physiology, Cellular Physiology, the Energetics of Living\nBeings._\u2014General physiology, as was taught by Pfl\u00fcger and his school,\nclaims to go deeper down than the apparatus, or the organ, or even\nthe cell. As in the case of physics, general physiology endeavours to\nreach, and really does in many cases reach, as far as the molecule.\nIt is not cellular, it is _molecular_. Already, in fact, the efforts\nof modern science have succeeded in penetrating into the most general\nphenomena of the living being\u2014those attributable to living matter,\nor, to speak more clearly, those which result from the play of the\nuniversal laws of matter at work in this particular medium which is the\norganized being.\n\nRobert Mayer and Helmholtz have the honour of having set physiology in\nthe right road. They founded _the energetics of living beings_\u2014_i.e._,\nthey regarded the phenomena of life from the point of view of energy,\nwhich is the factor of all the phenomena of the universe.\n\n\n\n\n CHAPTER I.\n\n ENERGY IN GENERAL.\n\n Origin of the Idea of Energy.\u2014The Phenomena of Nature bring into play\n only two Elements, Matter and Energy.\u2014\u00a7 1. Matter.\u2014\u00a7 2. Energy.\u2014\u00a7 3.\n Mechanical Energy.\u2014\u00a7 4. Thermal Energy.\u2014\u00a7 5. Chemical Energy.\u2014\u00a7 6.\n The Transformations of Energy.\u2014\u00a7 7. The Principles of Energetics.\u2014The\n Principle of the Conservation of Energy.\u2014\u00a7 8. Carnot\u2019s Principle.\u2014The\n Degradation of Energy.\n\n\n_Origin of the Idea of Energy._\u2014A new term, namely _energy_, has been\nfor some years introduced into natural science, and has ever since\nassumed a more and more important place. It is owing to the English\nphysicists, and especially to the English electrical engineers, that\nthis expression has made its way into technology, an expression which\nis part and parcel of both languages, and which has the same meaning\nin both. The idea it expresses is, in fact, of infinite value in\nindustrial applications, and that is why its use has gradually spread\nand become generalized. But it is not merely a practical idea. It is\nabove all a theoretical idea of capital importance to pure theory. It\nhas become the point of departure of a science, _energetics_, which,\nalthough born but yesterday, already claims to embrace, co-ordinate,\nand blend within itself all the other sciences of physical and living\nnature, which the imperfection of our knowledge alone had hitherto kept\ndistinct and apart.\n\nOn the threshold of this new science we find inscribed _the principle\nof the conservation of energy_, which has been presented to us by\nsome as Nature\u2019s supreme law, and which we may say dominates natural\nphilosophy. Its discovery marked a new era and accomplished a profound\nrevolution in our conception of the universe. It is due to a doctor,\nRobert Mayer, who practised in a little town in Wurtemberg, and who\nformulated the new principle in 1842, and afterwards developed its\nconsequences in a series of publications between 1845 and 1851. They\nremained almost unknown until Helmholtz, in his celebrated memoir on\nthe conservation of force, brought them to light and gave them the\nimportance they deserved. From that time forward the name of the doctor\nof Heilbronn, until then obscure, has taken its place among the most\nhonoured names in the history of science.[5]\n\n [5] Mayer\u2019s claim to fame has been disputed. A Scotch physicist, P.\n G. Tait, has investigated the history of the law of the conservation\n of energy, which is the history of the idea of energy. The conception\n has taken time to penetrate the human mind, but its experimental proof\n is of recent date. P. G. Tait finds an almost complete expression\n of the law of the conservation of energy in Newton\u2019s third law of\n motion\u2014namely, \u201cthe law of the equality of action and reaction,\u201d or\n rather, in the second explanation which Newton gave of that law. In\n fact, it was from this law that Helmholtz deduced it in 1847. He\n showed that the law of the equality of action and reaction, considered\n as a law of nature, involved the impossibility of perpetual motion,\n and the impossibility of perpetual motion is, in another form, the\n conservation of energy.\n\n At a meeting of the Academy of Science, at Berlin, 28th March 1878,\n Du Bois-Reymond violently attacked Tait\u2019s contention. The honour\n of having been the first to conceive of the idea of energy and\n conservation was awarded to Leibniz. Newton had no right to it, for\n he appealed to divine intervention to set the planetary system on its\n path when disturbed by accumulated perturbations. On the other hand,\n Colding claims to have drawn his knowledge of the law of conservation\n from d\u2019Alembert\u2019s principle. Whatever may be the theoretical\n foundations of this law, we are here dealing with its experimental\n proof. According to Tait, the proof can no more be attributed to R.\n Mayer than to Seguin. The real modern authors of the principle of the\n conservation of energy, who gave an experimental proof of it, are\n Colding, of Copenhagen, and Joule, of Manchester.\n\nAs for _energetics_, of which thermodynamics is only a section, it is\nagreed that even if it cannot forthwith absorb mechanics, astronomy,\nphysics, chemistry, and physiology, and build up that general science\nwhich will be in the future the one and only science of nature, it\nfurnishes a preparation for that ideal state, and is a first step in\nthe ascent to definite progress.\n\nHere I propose to expound these new ideas, in so far as they contain\nanything universally accessible; and in the second place, I propose to\nshow their application to physiology\u2014that is to say, to point out their\nr\u00f4le and their influence in the phenomena of life.\n\n_Postulate: the Phenomena of Nature bring into play only two Elements,\nMatter and Energy._\u2014If we try to account for the phenomena of the\nuniverse, we must admit with most physicists that they bring into play\ntwo elements, and two elements only; namely, _matter_ and _energy_. All\nmanifestations are exhibited in one or other of these two forms. This,\nwe may say, is the postulate of experimental science.\n\nJust as gold, lead, oxygen, the metalloids, and the metals are\ndifferent kinds of matter, so it has been recognized that sound, light,\nheat, and generally, the imponderable agents of the days of early\nphysics, are different varieties of energy. The first of these ideas\nis older and more familiar to us, but it has not for that reason a more\ncertain existence. Energy is objective reality for the same reason that\nmatter is. The latter certainly appears more tangible and more easily\ngrasped by the senses. But, upon reflection, we are assured that the\nbest proof of their existence, in both cases, is given by the law of\ntheir conservation\u2014that is to say, their persistence in subsisting.\n\nThe objective existence of matter and that of energy will therefore\nbe taken here as a postulate of physical science. Metaphysicians may\ndiscuss them. We have but little room for such a discussion.\n\n\n \u00a7 I. MATTER.\n\n\nIt is certainly difficult to give a definition of matter which will\nsatisfy both physicists and metaphysicians.\n\n_Mechanical Explanation of the Universe. Matter is Mass._\u2014Physicists\nhave a tendency to consider all natural phenomena from the point of\nview of mechanics. They believe that there is a mechanical explanation\nof the universe. They are always on the look out for it, implicitly or\nexplicitly. They endeavour to reduce each category of physical facts\nto the type of the facts of mechanics. They have made up their minds\nto see nowhere anything but the play of motion and force. Astronomy\nis celestial mechanics. Acoustics is the mechanics of the vibratory\nmovements of the air or of sonorous bodies. Physical optics has become\nthe mechanics of the undulations of the ether, after having been the\nmechanics of emission\u2014a wonderful mechanics which represents exactly\nall the phenomena of light, and furnishes us with a perfect objective\nimage of it. Heat, in its turn, has been reduced to a mode of motion,\nand thermodynamics claims to embrace all its manifestations. As early\nas 1812, Sir Humphry Davy wrote as follows:\u2014\u201cThe immediate cause of\nheat is motion, and the laws of transmission are precisely the same\nas those of the transmission of motion.\u201d From that time forth, this\nconception developed into what is really a science. The constitution\nof gases has been conceived by means of two elements\u2014particles, and\nthe motions of these particles, determined in the strictest detail.\nAnd finally, in spite of the difficulties of the representation of\nelectrical and magnetic phenomena after Amp\u00e8re and before Maxwell and\nHertz, physicists have been able to announce in the second half of the\nnineteenth century the unity of the physical forces realized in and\nby mechanics. From that time forth, all phenomena have been conceived\nas motion or modes of motion, only differing essentially one from the\nother in so far as motions may differ\u2014that is to say, in the masses of\nthe moving particles, their velocities, and their trajectories. The\nexternal world has appeared essentially homogeneous; it has fallen a\nprize to mechanics. Above all, there is heterogeneity in ourselves. It\nis in the brain, which responds to the nervous influx engendered by the\nlongitudinal vibration of the air, by the specific sensation of sound,\nwhich responds to the transverse vibration of the ether by a luminous\nsensation, and in general to each form of motion by an irreducible\nspecific sensation.\n\nForty years have passed since the mechanical explanation of the\nuniverse reached its definite and perfect form. It dominates physics\nunder the name of the _theory of kinetic energy_. The minds of men\nin our own time are so strongly impregnated with this idea that most\nscientists of ordinary culture get no glimpse of the world of phenomena\nbut by means of this conception. And yet it is only an hypothesis.\nBut it is so simple, so intuitive, and appears to be so thoroughly\nverified by experiment, that we have ceased to recognize its arbitrary\nand unnecessarily contingent character. Many physicists from this\nstandpoint consider the kinetic theory as an imperishable monument.\n\nHowever, as in the case of H. Poincar\u00e9, the most eminent physicists and\nmathematicians are not the dupes of this system; and without failing to\nrecognize the immense services which it has rendered to science, they\nare perfectly well aware that it is only a system, and that there may\nbe other systems. Certain among them, such as Ostwald, Mach, and Duhem,\nbelieve that the monument is showing signs of decay, and at present the\ntheory is opposed by another theory\u2014namely, the theory of _energy_.\n\nThe theory of _energy_ is usually considered and presented as a\nconsequence of the kinetic theory; but it is perfectly independent of\nit, and it is, in fact, without relying on the kinetic theory, without\nassuming the unity of physical forces, which are combined in molecular\nmechanics, that we shall expound the general system.\n\nThis is not the point at issue for the moment. It is not a question\nof deciding the reality or the merit of this or that mechanical\nexplanation; it is a question of something more general, because upon\nit depends the _idea of matter_. It is a question of knowing if there\nare any explanations other than mechanical. The illustrious English\nphysicist, Lord Kelvin, does not seem willing to admit this. \u201cI am\nnever satisfied,\u201d he said, in his _Molecular Mechanics_, \u201cuntil I have\nmade a mechanical model of the object. If I can make this model, I\nunderstand; if I cannot, I do not understand.\u201d\n\nThis tendency of so vigorous a mind to be content only with mechanical\nexplanations, has been that of the majority of scientific men up to the\npresent day, and from it has arisen the scientific idea of matter.\n\nWhat is matter, in fact, to the student of mechanics? It is mass. All\nmechanics is constructed of masses and forces. Laplace said: \u201cThe mass\nof a body is the sum of its material points.\u201d To Poisson, mass is the\nquantity of matter of which a body is composed. Matter is therefore\nconfused with mass. Now, mass is the characteristic of the motion of\na body under the action of a given force; it defines obedience or\nresistance to the causes of motion; it is the _mechanical parameter_;\nit is the co-efficient proper to every mobile body; it is the first\n_invariant_ of which a conception has been established by science.\n\nIn fact, the word matter appears to be used in other senses by\nphysicists, but this is only apparently so. They have but broadened the\nidea of the mechanicians. They have characterized matter by the whole\nseries of phenomenal manifestations which are _proportional to mass_,\nsuch as weight, volume, chemical properties\u2014so that we may say that the\nnotion of matter does not intervene scientifically with a different\nsignification from that of mass.\n\n_Two kinds of Matter. Ponderable and Imponderable._\u2014In physics we\ndistinguish between two kinds of matter\u2014ponderable, obeying the law of\nuniversal attraction or weight, and imponderable matter or ether, which\nwe assume to exist and to escape the action of that force. Ether has no\nweight, or extremely little weight. It is material in so far as it has\nmass. It is its mass which confers existence on it from the mechanical\npoint of view\u2014a logical existence, inferred from the necessity of\nexplaining the propagation of heat, light, or electricity.\n\nIt may be observed that the use of mass really comes to bringing\nanother element, force, to intervene, and we shall see that force is\nconnected with energy; thus it comes to defining matter indirectly by\nenergy. The two fundamental elements are not therefore irreducible; on\nthe contrary, they should be one and the same thing.\n\n_Energy is the only Objective Reality._\u2014This fusion into one will\nbecome more evident still when we examine the different kinds of\nenergy, each of which exactly corresponds to one of the aspects of\nactive matter. Shall we define matter by _extension_, by the portion\nof space it occupies, as certain philosophers do? The physicist will\nanswer that space is only known to us by the expenditure of energy\nnecessary to penetrate it (the activity of our different senses). And\nthen what is weight? It is _energy of position_ (universal attraction).\nAnd so with the other attributes. So that if matter were separated\nfrom the energetic phenomena by means of which it is revealed to\nus\u2014weight or energy of position, impenetrability or energy of volume,\nchemical properties or chemical energies, mass or capacity for kinetic\nenergy\u2014the very idea of matter would vanish. And that comes to saying\nthat fundamentally there is only one objective reality, _energy_.\n\n_Philosophical Point of View._\u2014But from the philosophical point of view\nare there objective realities? That is a wider question which throws\ndoubt upon matter itself, and which it is not our place to investigate\nhere. A metaphysician may always discuss and deny the existence of\nthe objective world. It may be maintained that man knows nothing\nbeyond his sensations, and that he only objectivates them and projects\nthem outside himself by a kind of hereditary illusion. We must avoid\ntaking sides in all these difficulties. Physics for the moment ignores\nthem\u2014_i.e._, postpones their consideration.\n\nIn a first approximation we agree to consider ponderable matter only.\nChemistry acquaints us with its different forms. They are the different\nsimple bodies, metalloids, metals, and the compound bodies, mineral\nor organic. Hence we may say that chemistry is _the history of the\ntransformations of matter_. From the time of Lavoisier this science has\nfollowed the transformations of matter, balance in hand, and ascertains\nthat they are accomplished without change of weight.\n\n_Law of the Conservation of Matter._\u2014Imagine a system of bodies\nenclosed in a closed vessel, and the vessel placed in the scale of a\nbalance. All the chemical reactions capable of completely modifying the\nstate of this system have no effect upon the scale of the balance. The\ntotal weight is the same before, during, and after. It is precisely\nthis equality of weight which is expressed in all the equations with\nwhich treatises on chemistry are filled.\n\nFrom a higher point of view we recognize here, in this _law of\nLavoisier_ or of the _conservation of weight_, the verification of one\nof the great laws of nature which we extend to every kind of matter,\nponderable or not. It is the _law of the conservation of matter_, or\nagain, of the indestructibility of matter\u2014\u201cNothing is lost, nothing\nis created, all is transformation.\u201d This is exactly what Tait held,\nthis impossibility of creating or destroying matter which at the same\ntime is a proof of its objective existence. This indestructibility\nof ponderable matter is at the same time the fundamental basis of\nchemistry. Chemical analysis could not exist if the chemist were not\nsure that the contents of his vessel at the end of his operations ought\nto be quantitatively, that is to say by weight, the same as at the\nbeginning, and during the whole course of the experiment.[6]\n\n [6] It must be added that the absolute rigour of this law has been\n called in question in recent researches. It would only have an\n approximate value.\n\n\n \u00a7 2. ENERGY.\n\n\n_The Idea of Energy Derived from the Kinetic Theory._\u2014The notion of\nenergy is not less clear than the notion of matter, it is only more\nnovel to our minds. We are led to it by the mechanical conception which\nnow dominates the whole of physics, _the kinetic conception_, according\nto which in the sensible universe there are no phenomena but those of\nmotion. Heat, sound, light, with all their manifestations so complex\nand so varied, may, according to this theory, be explained by motion.\nBut then, if outside the brain and the mind which has consciousness and\nwhich perceives, Nature really offers us only motion, it follows that\nall phenomena are essentially homogenous among one another, and that\ntheir apparent heterogeneity is only the result of the intervention of\nour sensorium. They differ only in so far as movements are capable of\ndiffering\u2014that is to say, in velocity, mass, and trajectory. There is\nsomething fundamental which is common to them and this _quid commune_\nis _energy_. Thus the idea of energy may be derived from the kinetic\nconception, and this is the usual method of exposition.\n\nThis method has the great inconvenience of causing an idea which lays\nclaim to reality to depend upon an hypothesis. And besides that, it\ngives a view of it which may be false. It makes of the different forms\nof energy something more than varieties which are equivalent to one\nanother. It makes of them _one and the same thing_. It blends into one\nthe modalities of energy and mechanical energy. For the experimental\nidea of equivalence, the kinetic theory substitutes the arbitrary idea\nof the equality, the blending, and the fundamental homogeneity of\nphenomena. This no doubt is how the founders of energetics, Helmholtz,\nClausius, and Lord Kelvin understood things. But a more attentive study\nand a more scrupulous determination not to go beyond the teaching\nof experiment should compel us to reform this manner of looking at\nit. And it is Ostwald\u2019s merit that, after Hamilton, he insisted on\nthis truth\u2014that the various kinds of physical magnitudes furnished\nby the observation of phenomena are different and characteristic. In\nparticular, we may distinguish among them those which belong to the\norder of _scalar_ magnitudes and others which are of the order of\n_vector_ magnitudes.\n\n_The Idea of Energy derived from the Connection of Phenomena._\u2014The idea\nof energy is not absolutely connected with the kinetic theory, and it\nshould not be exposed therefore to the vicissitudes experienced by that\ntheory. It is of a higher order of truth. We can derive it from a less\nunsafe idea, namely that of the _connection of natural phenomena_. To\nconceive it we must get accustomed to this primordial truth, that there\nare no _phenomena isolated_ in time and space. This statement contains\nthe whole point of view of energetics.\n\nThe physics of early days had only an incomplete view of things, for it\nconsidered phenomena independently the one of the other.\n\nPhenomena for purposes of analysis were classed in separate and\ndistinct compartments: weight, heat, electricity, magnetism, light.\nEach phenomenon was studied without reference to that it succeeded or\nthat which should follow. Nothing could be more artificial than such a\nmethod as this. In fact, there is a sequence in everything, everything\nis connected up, _everything precedes and succeeds in nature_\u2014in\nnature there are only series. The isolated fact without antecedent or\nconsequent is a myth. Each phenomenal manifestation is in solidarity\nwith another. It is a metamorphosis of one state of things into\nanother. It is transformation. It implies a state of things anterior to\nthat which we are observing, a phenomenal form which has preceded the\nform of the present moment.\n\nNow there exists a link between the anterior state and the succeeding\nstate\u2014that is to say, between the new form which is appearing and the\npreceding form which is disappearing. The science of energy shows\nthat something has passed from the first condition to the second,\nbut covering itself as it were with a new garment; in a word, that\nsomething active and permanent subsists in the passage from one\ncondition to another, and that what has changed is only the aspect, the\nappearance.\n\nThis constant something which is perceived beneath the inconstancy and\nthe variety of forms, and which circulates in a certain manner from the\nantecedent phenomenon to its successor, is energy.\n\nBut still this is only a very vague view, and it may seem arbitrary.\nIt may be made more exact by examples borrowed from the different\ncategories of natural phenomena. There are energetic modalities in\nrelation with the different phenomenal modalities. The different orders\nof phenomena which may be presented\u2014mechanical, chemical, thermal,\nelectrical\u2014give rise to corresponding forms of energy.\n\nWhen to a mechanical phenomenon succeeds a mechanical, thermal,\nor electrical phenomenon, we say, embracing transformation in its\ntotality, that there has been a transformation of mechanical energy\ninto another form of energy, mechanical, thermal, or electrical, etc.\n\nThis idea becomes more precise if we examine successively each of these\ncases and the laws which regulate them.\n\n\n \u00a7 3. MECHANICAL ENERGY.\n\n\nMechanical energy is the simplest and the oldest known.\n\n_Mechanical Elements: Time, Space, Force, Work, Power._\u2014Mechanical\nphenomena may be considered under two fundamental conditions\u2014_time_ and\n_space_, which are, in a measure, logical elements, to which may be\njoined a third element, itself experimental, having its foundations in\nour sensations\u2014namely, _force_, _work_, or _power_.\n\nThe ideas of force, work, and power, are drawn from the experience man\nhas of his muscular activity. Nevertheless the greatest mathematical\nminds from from Descartes to Leibniz have been obliged to define and\nexplain them clearly.\n\n_Force_.\u2014The prototype of force is weight, universal attraction.\nExperiment shows us that every body falls as long as no obstacle\nopposes its fall. This is so universal a property of matter that it\nserves to define it. The _force_, weight, is therefore the name given\nto the cause of the fall of the bodies.\n\nForce in general is the _cause of motion_. Hence force exists only in\nso far as there is motion. There would be no force without action. This\nis Newton\u2019s point of view. It did not prevail, and was not the point\nof view of his successors. The name of force has been given not only\nto the cause which produces or modifies motion, but to the cause which\nresists and prevents it. And then not only have _forces in action_ been\nconsidered (dynamics), but _forces at rest_ (statics). Now, to Newton\nthere was no statics. Forces do not continue to exist when they produce\nno motion; they are not in equilibrium, they are destroyed.\n\nThe idea of force therefore is a metaphysical idea which contains the\nidea of _cause_. But it becomes experimental immediately it is looked\nupon as resisting motion, according to the point of view of Newton\u2019s\nopponents. Its foundations lie in the muscular activity of man.\n\nMan can support a burden without bending or moving. This burden is\na weight\u2014that is to say, a mass acted on by the force of weight.\nMan resists this force so as to prevent its effect. If it were not\nannihilated by man\u2019s _effort_, this effect would be the motion or\nthe fall of the heavy body. The _effort_ and the force are thus in\nequilibrium, and the effort is equal and opposite to the force. It\ngives to the man who exercises it the conscious idea of _force_. Thus\nwe know of force through effort. Every clear idea that we can have of\n_force_ springs from the observation of our muscular effort.\n\nThe notion of force is thus an anthropomorphic notion. When an effect\nis produced in nature outside human intervention, we say that it is\nby something analogous to what in man is effort, and we give to this\nsomething a name which is also analogous, namely _force_. To give a\nname to _effort_ and to compare efforts in magnitude, we need not know\nall about them, nor need we know in what they essentially consist, of\nwhat series of physical, chemical, and physiological actions they are\nthe consequence. And so it is with force. It is a resistance to motion\nor the cause of motion. This cause of motion may be an anterior motion\n(kinetic force). It may be an anterior physical energy (physical and\nchemical forces).\n\nForces are measured in the C.G.S. system by comparing them with the\nunit called the Dyne.[7] In practice they are compared with a much\nlarger unit\u2014the gramme, which is the weight, the force acting on a unit\nof mass of one centimetre of distilled water at a temperature of 4\u00b0 C.\n\n [7] The dyne is the force which applied to the unit of mass produces a\n unit of acceleration.\n\n_Work._\u2014The muscular activity of man may be brought into play in yet\nanother manner. When we employ workmen, as Carnot said in his _Essai\nsur l\u2019\u00e9quilibre et le mouvement_, it is not a question of \u201cknowing the\nburdens that they can carry without moving from their position,\u201d but\nrather the burdens that they can carry from one point to another. For\ninstance, a workman may have to lift the water from the bottom of a\nwell to a given height, and the case is the same for the animals we\nemploy. \u201cThis is what we understand by force when we say that the force\nof a horse is equal to the force of seven men. We do not mean that if\nseven men were pulling in one direction and the horse in another that\nthere would be equilibrium, but that in a piece of work the horse alone\nwould lift, for example, as much water from the bottom of a well to a\ngiven height as the seven men together would do in the same time.\u201d[8]\n\n [8] These words spoil the statement, for time has nothing to do with\n it.\n\nHere, then, we have to do with the second form of muscular activity,\nwhich is called in mechanics, \u201cwork\u201d\u2014at least, if in the preceding\nquotation we attach no particular importance to the words \u201cin the same\ntime,\u201d and retain the employment of muscular activity only \u201cunder\nconstant conditions.\u201d Mechanical work is compared with the elevation of\na certain weight to a certain height. It is measured by the product of\nthe force (understood in the sense in which it was used just now\u2014that\nis to say, as causing or resisting motion) and the displacement due to\nthis motion. The unit is the Kilogrammetre\u2014that is to say, the work\nnecessary to lift a weight of one kilogramme to the height of one\nmetre.\n\nIt will be remarked that the idea of time does not intervene in our\nestimation of work. The notion of work is independent of the ideas\nof velocity and time. \u201cThe greater or less time that we take to do a\npiece of work is of no more assistance in measuring its magnitude than\nthe number of years that a man may have taken to grow rich or to ruin\nhimself can help to estimate the present amount of his fortune.\u201d\n\nGoing back to Carnot\u2019s comparison, an employer who employed his workmen\nonly on piece-work,\u2014that is to say, who would only care about the\namount of work done, and would be indifferent to the time that they\ntook over it,\u2014would be at the same point of view as the advocates of\nthe mechanical theory. M. Bouasse, whom we follow here, has remarked\nthat this idea of mechanical work may be traced back to Descartes. His\npredecessors, and Galileo in particular, had quite a different idea of\nthe way in which mechanical activity should be measured; and so, among\nthe mathematicians of the eighteenth century, Leibniz and, later, John\nBernoulli were almost alone in looking at it from this point of view.\n\n_Energy._\u2014Work thus understood is _mechanical energy_. It represents\nthe lasting and objective effect of the mechanical activity independent\nof all the circumstances under which it was carried out. The same\nwork may be done under very different conditions of time, velocity,\nforce, and displacement. It is therefore the permanent element in the\nvariety of mechanical aspects. Work, for example, in the collision of\nbodies when the motion of a body appears to be destroyed on impact\nwith another, reappears as indestructible _vis viva_. This, then, is\nexactly what we call _energy_; and if we agree to give it this name,\nwe may say that the conservation of energy is invariable throughout all\nmechanical transformations.\n\n_Distinction between Work and Force, and between Energy and Work._\u2014The\nhistory of mechanics shows us what trouble has been taken and what\nefforts have been made to distinguish work (now mechanical energy) from\nforce.\n\nIt is worth while insisting on this distinction. It could be easily\nshown that force has no objective existence. It has no duration,\nno permanence. It does not survive its effect, motion. There is no\nconservation of force. It passes instantly from infinity to zero.\nIt is a _vectorial magnitude_\u2014that is to say, it involves the idea\nof direction. Work, on the other hand, is the real element; it is\na _scalar magnitude_ involving the idea of opposite directions,\nindicated by the signs + and-. Work and force are heterogeneous\nmagnitudes. Energy, and this is the only characteristic by which it is\ndistinguished from work, is an _absolute magnitude_ to which we may not\neven give opposite signs.\n\nAn example may perhaps throw these characteristics into relief\u2014namely,\nthe hydraulic press. We have on the platform exactly the work which has\nbeen done on the other side. The machine has only made it change its\nform. On the contrary, the force has been infinitely multiplied. We\nmay, in fact, consider an infinite number of surfaces equal to that of\na small piston, placed and orientated at will within the liquid; each,\naccording to Pascal\u2019s principle, will support a pressure equal to that\nwhich is exercised. As soon as we cease to support it, this infinity\nfalls at once to zero. Now what real thing could pass instantly from\ninfinity to zero?\n\nThat skilful and very able physiologist, M. Chauveau, has endeavoured\nto use the same term _energy of contraction_ for the two phenomena of\neffort (force) and work. It seems, however, from the point of view\nof the expenditure imposed on the organism, that these two modes of\nactivity, _static contraction_ (effort), and _dynamical contraction_\n(work), may be, in fact, perfectly comparable. But although this manner\nof conceiving the phenomena may certainly be exact, and may be of great\nvalue, the idea of force must none the less remain distinct from that\nof work. The persistence of the author in violating established custom\nin this connection has prevented him from enabling mechanicians and\neven some physiologists to understand and accept very useful truths.\n\n_Power._\u2014The idea of mechanical _power_ differs from those of force\nand work. The idea of time must intervene. It is not sufficient, in\nfact, in order to characterize a mechanical operation, to point to\nthe task accomplished. It may be necessary or useful to know how much\ntime it required. This is true, especially when we are concerned with\nthe circumstances as well as the results of the performance of the\nwork; and this is the case when we wish to compare machines. We say\nthat the machine which does the work in the shortest space of time is\nthe most powerful. The unit of power is the Kilogrammetre-second\u2014that\nis to say, the power of a machine which does a kilogrammetre in a\nsecond. In manufactures we generally employ a unit 75 times greater\nthan this\u2014a _horse-power_. This is the power of a machine which does\n75 kilogrammetres a second. In the electrical industry we measure by\n_kilowatts_, which are equivalent to 1.36 horse power, or by a _watt_,\na unit a thousand times smaller.\n\nLet us add that the power of a machine is not an absolute and permanent\ncharacteristic of the machine. It depends on the circumstances under\nwhich the work is carried out, and that is why, in particular, we\ncannot appreciate the power of the human machine in comparison with\nindustrial machines. Experience has shown that the mechanical power\nof living beings depends upon the nature of the work they are doing.\nIn this connection we may mention some very interesting experiments\ncommunicated to the Institute, in the year VI., by the celebrated\nphysicist, Coulomb. A man of the average weight of 70 kilogrammes was\nmade to climb the stairs of a house 20 metres high. He ascended at the\nrate of 14 metres a minute, and he performed this daily task for four\neffective hours. This work was equivalent to 235,000 kilogrammetres.\nBut if, instead of climbing without a burden, the same man had had to\ncarry a load, the result would have been quite different. Coulomb\u2019s\nworkman took up six loads of wood a day to a height of 12 metres in 66\njourneys, corresponding to a maximum work of 109,000 instead of 235,000\nkilogrammetres. The mechanical power of the human machine thus varied\nin the two cases in the ratio of 235 to 109.\n\n_The Two Aspects of Mechanical Energy: Kinetic and Potential._\u2014Energy,\nor mechanical work, may present itself in two forms\u2014kinetic energy,\ncorresponding to the mechanical phenomenon which has really taken\nplace, and _potential energy_, or the energy of reserve.\n\nA body which has been raised to a certain height will, if it be let\nfall, perform work which can be exactly measured in kilogrammetres by\nthe product of its weight into the height it falls. Such work may be\nutilized in many ways. In this way, for instance, public clocks are\nworked. Now, as long as the clock-weight is raised and not let go, and\nas long as it is motionless, the physics of early days would say that\nthere is nothing to discuss; the phenomenon is the fall; it is going to\ntake place, but at the present moment there has been no fall.\n\nIn energetics we do not reason in this way. We say that the body\npossesses a _capacity for work_ which will be manifested when the\nopportunity arises, a storage of energy, a virtual or _potential\nenergy_, or again, an _energy of position_, which will be transformed\ninto actual energy or real work as soon as the body falls.\n\nLet us ask whence this energy arises. It proceeds from the previous\noperation which has raised the weight from the surface of the soil\nto the position it occupies. For example, if it is a question of the\nweights of a public clock, which, by its fall, will develop in 15\ndays the work that is necessary to turn the wheels, to strike the\nbell, and to turn the hands, this work ought to bring to our minds the\nexactly equal and opposite work done by the clockmaker, who has to\ncarry the clock-weight and to lift it up from the ground to its point\nof departure. The work of the fall is the faithful counterpart of the\nwork of elevation. The phenomenon has therefore in reality two phases.\nWe find in the second exactly what was put into the first, the same\nquantity of energy\u2014_i.e._, the same work. Between these phases comes\nthe intermediary phase of which we say that it is a period of virtual\n_or potential energy_. This is a way of remembering in some measure the\npreceding phenomenon\u2014_i.e._, the work of lifting up, and of indicating\nthe phenomena which will follow\u2014_i.e._, the work of the fall. And thus\nwe connect by our thoughts the present situation with the antecedent\nand with the consequent position, and it is from this consideration of\ncontinuity alone that the conception of energy springs\u2014that is to say,\nof something which is conserved and is found to be permanent in the\nsuccession of phenomena. This energy of which we lose no trace does\nnot appear to us new when it is manifested. Our imagination eventually\nmaterializes the idea of it. We follow it as a real thing, having\nan objective existence, which is asleep during the latent potential\nperiod, and is revealed or manifested later.\n\nAmong other examples, that of the coiled spring which is unwound is\nparticularly suitable for showing this fundamental character of the\nidea of mechanical energy, an idea which is the clearest of all.\nMachines are only transformers and not creators of mechanical energy.\nThey only change one form into another.\n\nIn the same way, too, a stream of water or the torrent of a mountainous\nregion may be utilized for setting in motion the wheels and the\nturbines of the factories situated in the valley. Its descent produces\nthe mechanical work which would be a creation _ex nihilo_ if we do not\nconnect the phenomenon with its antecedents. We look on it as a simple\nrestitution, if we think of the origin of this water which has been\ntransported and lifted in some way to its level by the play of natural\nforces\u2014evaporation under the action of the sun, the formation of\nclouds, transport by winds, etc. And we here again see that a complex\nenergy has been transformed, in its first phenomenal condition, into\n_potential energy_, and that this potential energy is always expended\nin the second phase without loss or gain.\n\n_The Different Kinds of Mechanical Energy; of Motion, of\nPosition._\u2014There are as many forms of energy as there are distinct\ncategories of phenomena or of varieties in these categories. Physicists\ndistinguish between two kinds of mechanical energy\u2014energy of motion\nand energy of position. The energy of position presents several\nvariants\u2014energy of distance, which corresponds to force: of this we\nhave just spoken; energy of surface, which corresponds to particular\nphenomena of surface tension; and energy of volume which corresponds\nto the phenomena of pressure. Energy of motion, _kinetic energy_, is\nmeasured in two ways: as work (the product of force and displacement,\nW = _fs_) or as _vis viva_ (half the product of the mass into the square\nof the velocity U = _mv^2_\u22152.)[9]\n\n [9] We therefore notice that the measures of force and work bring in\n mass, space, and time. The typical force, weight, is given by w = mg.\n On the other hand, we have by the laws of falling bodies _v_ = _gt_;\n _s_ = 1\u22152_gt^2_; whence _g_ = 2_s_\u2215_t^2_; _w_ = _m_(2_s_\u2215_t^2_); or,\n if F be the force, M the mass, L the space described, and T the time,\n we have F = MLT^{-2}, which expresses what are called the dimensions\n of the force\u2014that is to say, the magnitudes with their degree, which\n enter into its expression. We may thus easily obtain the dimensions of\n work:\u2014\n\n _Work_ = _f_ \u00d7 _s_ = _mv^2_\u22152 = ML^2T^{-2}.\n\n\n \u00a7 4. THERMAL ENERGY.\n\n\nIn the elements of physics it is nowadays taught that mechanical\nwork may be transformed into heat, and reciprocally that heat may be\ntransformed into mechanical work. Friction, impact, pressure, and\nexpansion destroy or annihilate the mechanical energy communicated to\na body or to the organs of a machine. With the disappearance of motion\nwe note the appearance of heat. Examples abound. The tyre of a wheel\nis heated by the friction of the road. Portions of steel are warmed\nby the impact with stone, as in the old flint and steel. Two pieces\nof ice were melted by Davy, who rubbed them one against the other,\nthe external temperature being below zero. The boiling of a mass of\nwater caused by a drill was noticed by Rumford in 1790, during the\nmanufacture of bronze cannon. Metal, beaten on an anvil, is heated. A\nleaden ball flattened against a resisting obstacle shows increase of\ntemperature carried to the point of fusion. Finally, and symbolically,\nwe have the origin of fire in the fable of Prometheus, by rubbing\ntogether the pieces of wood which the Hindoos called _pramantha_.\nCorrelation is constant between the thermal and mechanical phenomena,\na correlation that becomes evident as soon as observers have ceased to\nrestrict themselves to the determination in isolation of the one fact\nor the other. There is never any real destruction of heat and motion\nin the true sense of the word; what disappears in one form appears\nagain in another; just as if something indestructible were appearing in\na series of successive disguises. This impression is translated into\nwords when we speak of the metamorphosis of mechanical into thermal\nenergy.\n\n_The Mechanical Equivalent of Heat._\u2014The interpretation assumes a\nremarkable character of precision, which at once strikes the mind\nwhen physics applies to these transformations the almost absolute\naccuracy of its measurements. We then find that the rate of exchange\nis invariable. Transformations of heat into motion, and of motion into\nheat, take place according to a rigorous numerical law, which brings\ninto exact correspondence the quantity of each. Mechanical effect\nis estimated, as we have seen, by work, that is in kilogrammetres.\nHeat is measured in calories, the calorie being the quantity of heat\nnecessary to raise from 0\u00b0C to 1\u00b0C a kilogramme of water (Calorie) or\none gramme of water (calorie). It is found that whatever may be the\nbodies and the phenomena which serve as intermediaries for carrying\nout this transformation, we must always expend 425 kilogrammetres to\ncreate a Calorie, or expend 0\u00b700234 Calories to create a kilogrammetre.\nThe number 425 is the mechanical equivalent of the Calorie, or, as\nis incorrectly stated, of the heat. It is this constant fact which\nconstitutes _the principle of the equivalence of heat and of mechanical\nwork_.\n\n\n \u00a7 5. CHEMICAL ENERGY.\n\n\nWe cannot yet actually measure chemical activity directly, but we know\nthat chemical action may give rise to all other phenomenal modalities.\nIt is their most ordinary source, and it is to it that industries\nappeal to obtain heat, electricity, and mechanical action. In the\nsteam engine, for instance, the work that is received arises from the\ncombustion of carbon by the oxygen of the air. This gives rise to the\nheat which vaporizes the water, produces the tension of the steam,\nand ultimately produces the displacement of the piston. The theory of\nthe steam engine might be reduced to these two propositions: chemical\nactivity gives rise to heat, and heat gives rise to motion; or to use\nthe language to which the reader by now will be accustomed, chemical\nenergy is transformed into thermal energy, and that into mechanical\nenergy. It is a series of phases and of instantaneous changes, and the\nexchange is always affected according to a fixed rate.\n\n_The Measurement of Chemical Energy._\u2014Our knowledge of chemical energy\nis less advanced than that of the energies of heat and sensible motion.\nWe have not yet reached the stage of numerical verifications. We can\nonly therefore affirm the equivalence of chemical and thermal energies\nwithout the aid of numerical constants, because we do not yet, in\nthe present state of science, know how to measure chemical energy\ndirectly. Other known energies are always the product of two factors:\nthe mechanical energy of position, or work, is measured by the product\nof the force _f_, and the displacement _s_; work = _fs_; the mechanical\nenergy of motion, U = 1\u22152_mv^2_, is measured by the product of the mass\ninto half the square of the velocity. Thermal energy is measured by\nthe product of the temperature and the specific heat; electric energy\nby the product of the quantity of electricity (in coulombs) and of the\nelectromotive force (in volts). As for chemical energy, we guess that\nit may be valued directly according to Berthollet\u2019s system, adopted by\nthe Norwegian chemists, Guldberg and Waage, by means of the product of\nthe masses and of a force, or co-efficient of affinity, which depends\non the nature of the substances which are brought together, on the\ntemperature, and on the other physical circumstances of the reaction.\nOn the other hand, the researches of M. Berthelot enable us in many\ncases to obtain an indirect valuation in terms of the equivalent heat.\n\n_Its Two Forms._\u2014It is interesting to note that chemical energy may\nalso be regarded from the two states of _potential_ and _kinetic\nenergy_. The coal-oxygen system, to burn in the furnace of the steam\nengine, must be primed by preliminary work (local ignition), just as\nthe weight that is raised and left motionless at a certain height\nrequires a small effort to be detached from its support. When this\ncondition is fulfilled, energy is at once manifest. We must admit that\nit existed in the latent state, in the state of _chemical potential\nenergy_. Under the impulse received, the carbon combines with the\noxygen and forms carbonic acid, C + 2O becomes CO\u2304{2}; potential energy\nis changed into actual chemical energy, and immediately afterwards into\nthermal energy. We should have only a very incomplete and fragmentary\nview of the reality of things if we were to consider this phenomenon\nof combustion in isolation. We must consider it in connection with\nwhat has actually created the energy which it is about to dissipate.\nThis antecedent fact is the action of the sun upon the green leaf. The\ncarbon which burns in the furnace of the machine comes from the mine in\nwhich it was stored in the form of coal\u2014that is to say, of a product\nwhich was vegetable in its primitive form, and which was formed at the\nexpense of the carbonic acid of the air. The plant had separated, at\nthe expense of the solar energy, the carbon from the oxygen to which it\nwas united in the carbonic acid of the atmosphere. It had created the\nsystem C + 2O. So that the solar energy produces the chemical potential\nenergy which was so long before it was utilized. Combustion expends\nthis energy in making carbonic acid over again.\n\n_Materialization of Energy._\u2014The fertility of the idea of energy is\ntherefore, as we see from all these examples, due to the relations\nit establishes between the natural phenomena of which it exhibits\nthe necessary relation, destroyed by the excessive analysis of early\nscience. It shows us that in the world of phenomena there is nothing\nbut transformations of energy. And we regard these transformations\nthemselves as the circulation of a kind of indestructible agent which\npasses from one form of determination to another, as if it were\nsimply putting on a fresh disguise. If our intellect requires images\nor symbols to embrace the facts and to grasp their relation, it may\nintroduce them here. It will materialize energy, it will make of it a\nkind of imaginary being, and confer upon it an objective reality. And\nfor the mind, as long as it does not become the dupe of the phantom\nwhich it itself has created, this is an eminently comprehensive\nartifice which enables us to grasp readily the relations between\nphenomena and their bond of affiliation.\n\nThe world appears to us then, as we said at the outset, constructed\nwith singular symmetry. It offers to us nothing but transformations of\nmatter and transformations of energy; these two kinds of metamorphoses\nbeing governed by two laws equally inevitable, the conservation\nof matter and the conservation of energy. The first of these laws\nexpresses the fact that matter is indestructible, and passes from\none phenomenal determination to another at a rate of equivalence\nmeasured by weight; the second, that energy is indestructible, and\nthat it passes from one phenomenal determination to another at a rate\nof equivalence fixed for each category by the discoveries of the\nphysicists.\n\n\n \u00a7 6. TRANSFORMATIONS OF ENERGY.\n\n\nThe idea of energy has become the point of departure of a science,\n_Energetics_, to the establishment of which a large number of\ncontemporary physicists, among whom are Ostwald, Le Ch\u00e2telier, etc.,\nhave devoted their efforts. It is the study of phenomena, regarded\nfrom the point of view of _energy_. I have said that it claims to\nco-ordinate and to embrace all other sciences.\n\nThe first object of energetics should be the consideration of the\ndifferent forms of energy at present known, their definition and their\nmeasurement. This is what we have just done in broad outline.\n\nIn the second place, each form of energy must be regarded with\nreference to the rest, so as to determine if the transformation of this\ninto that is directly realizable, and by what means, and, finally,\naccording to what rate of equivalence. This new chapter is a laborious\ntask which would compel us to traverse the whole field of physics.\n\nOf this long examination we need only concern ourselves here with three\nor four results which will be more particularly important in the case\nof applications to living beings. They refer to mechanical energy, to\nthe relations of thermal energy and chemical energy, to the complete\nr\u00f4le of thermal energy, and finally to the extreme adaptability of\nelectrical energy.\n\n1. _Transformation of Mechanical Energy._\u2014Mechanical energy may change\ninto every other form of energy, and all others can change into it,\nwith but one exception, that of chemical energy. Mechanical effort does\nnot produce chemical combination. What we know of the part played by\npressure in the reactions of dissociation seems at first to contradict\nthis assertion. But this is only in appearance. Pressure intervenes in\nthese operations only as _preliminary work_ or _priming_, the purpose\nof which is to bring the bodies into contact in the exact state in\nwhich they must be for the chemical affinities to be able to enter into\nplay.\n\n2. _Transformation of Thermal Energy; Priming._\u2014Thermal (or luminous)\nenergy does not change directly into chemical energy. In fact, heat and\nlight favour and even determine a large number of chemical reactions;\nbut if we go down to the foundation of things we are not long before\nwe feel assured that heat and light only serve in some measure for\n_priming_ for the phenomenon, for preparing the chemical action, for\nbringing the body into the physical state (liquid, steam) or to the\ndegree of temperature (400\u00b0 C. for instance, for the combination of\noxygen and hydrogen) which are the preliminary indispensable conditions\nfor the entry upon the scene of chemical affinities.\n\nOn the contrary, chemical energy may really be transformed into\nthermal energy. We have an instance of this in the reactions which\ntake place without the aid of external energy; and again, in those\nvery numerous cases which, such as the combustion of hydrogen and\ncarbon, or the decomposition of explosives, the reactions continue\nwhen once primed. I may make a further observation apropos of thermal\nand photic energy. These are not two really and essentially distinct\nforms, as was thought in the early days of physics. When we consider\nthings objectively, there is absolutely no light without heat; light\nand heat are one and the same agent. According as it is at this or\nthat degree of its scale of magnitude, it makes a stronger impression\non the skin (sensation of heat) or on the retina (sensation of light)\nof man and animals. The difference may be put down to the diversity of\nthe work and not to that of the agent. The kinetic theory shows us that\nthe agent is qualitatively identical. The words heat and light only\nexpress the chance of the meeting of the radiant agent with a skin and\na retina. At the lowest degree of activity this agent exerts no action\non the terminations of the thermal cutaneous nerves, nor on the optic\nnerve-terminations. As this degree is raised the former of these nerves\nare affected (cold, heat) and are so to the exclusion of the nerves of\nvision. Then they are both affected (sensation of heat and light), and\nfinally, beyond that, sight alone is affected. The transformation of\none energy into the other is therefore here reduced to the possibility\nof increasing or decreasing the intensity of the action of this common\nagent in the exact proportions suitable for passing from one of the\nconditions to the other; and this is easy when it is a question of\ngoing up the scale in the case of light, and, on the contrary, it is\nnot realizable directly, that is to say without external assistance,\nwhen it is a question of going down the scale again, in the case of\nheat.\n\n3. _Heat a Degraded Form of Energy._\u2014We have seen that thermal energy\nis not directly transformed into chemical energy. There is yet another\nrestriction in the case of this thermal energy if we study the laws\nwhich govern the circulation and the transformations of thermal energy;\nand the most important comes from the impossibility of transporting it\nfrom a body at a lower temperature to a body at a higher temperature.\nOn the whole, and because of these restrictions, thermal energy is an\nimperfect variety of universal energy, or, as the English physicists\ncall it, a degraded form.\n\n4. _Simple Transformations of Electrical Energy. Its Intermediary\nR\u00f4le._\u2014On the other hand, electrical energy represents a perfected and\ninfinitely advantageous form of this same universal energy, and this\nexplains the vast development of its industrial applications within\nless than a century. It is not that it is better known than the others\nin its nature and in the secret of its action. On the contrary, there\nis more dispute than ever as to its nature. To some, electricity,\nwhich is transported and propagated with the speed of light, is a real\nflux of the ether as was taught by Father Secchi, who compared it to a\ncurrent of water in a pipe. It would do its work, just as the water of\nthe mill does its work by flowing over a wheel or through a turbine.\nElectricity, like water in this case, would not be an energy in itself,\nbut a means of transporting energy.\n\nTo others, such as Clausius, Hertz, and Maxwell, it is not so; the\nelectric current is not a transport of energy. It is a state of the\nether of a peculiar, specific kind, periodically produced (electric\noscillation), and propagated with a speed of the order of that of light.\n\nHowever that may be, what constitutes the essential peculiarity\nof electrical energy, and what causes its value, is that it is an\nincomparable agent of transformation. Every known form of energy\nmay be converted into it, and inversely, electrical energy may be\nchanged with the utmost facility into all other energies. This extreme\nadaptability assigns to it the part of an intermediary between the\nother less tractable agents. Mechanical energy, for instance, lends\nitself with difficulty to the production of light, that is to say, to\na metamorphosis into photic energy (a variety of thermal energy). A\nfall of water cannot be directly utilized for lighting purposes. The\nmechanical work of this fall, which cannot be exploited in its present\nform, serves to set in motion in industrial lighting the installations,\nthe electric machines, and the dynamos which feed the incandescent\nlamps. Mechanical work is changed into electrical energy, and it, in\nits turn, into thermal or photic energy. Electricity has here played\nthe part of a useful intermediary.\n\nThe last part of energetics must be consecrated to the study of the\ngeneral principles of this science. These principles are two in number,\nthe principle of the _conservation of energy_, or Mayer\u2019s principle,\nand the principle of the transformation of energy, or Carnot\u2019s\nprinciple. The doctrine of energy thus reduces to two fundamental laws\nthe multitude of laws, often known as \u201cgeneral,\u201d to which natural\nscience is subject.\n\n\n \u00a7 7. THE PRINCIPLE OF THE CONSERVATION OF ENERGY.\n\n\nIn all that precedes, the principle of conservation has intervened at\nevery step. In fact, the very idea of energy is connected with the\nexistence of this principle. We first discover the idea in the work of\nthe philosophical mathematicians who established the foundations of\nmechanics:\u2014Newton, Leibniz, d\u2019Alembert, and Helmholtz; or of inductive\nphysicists such as Lord Kelvin. Its experimental proof, sketched by\nMarc Seguin and R. Mayer, is due to Colding and Joule.\n\n_It is Independent of the Kinetic Theory._\u2014Mayer\u2019s law states that\nenergy is indestructible; that all phenomenality is nothing but a\ntransformation of energy from one form to another, and that this\ntransformation takes place either at equal values, or rather, at a\ncertain rate of equivalence. This is what takes place when thermal\nenergy is transformed into mechanical energy (equivalent 425). This\nrate of equivalence is fixed by the researches of physicists for each\ncategory of energy.\n\nIt will be noticed that this law and this theory of energy, which\nis always presented by authors of elementary books as a consequence\nof the kinetic theory, is quite independent of it. In the preceding\nlines we have not even mentioned its name. We have not assumed that\nall phenomena are movements or transformations of movements, whether\nsensible or vibratory; we have not affirmed that what was passing from\none phenomenal determination to another was the _vis viva_ of the\nmotion, as is the case in the impact of elastic bodies. No doubt the\nkinetic theory affords us a very striking image of these truths which\nare independent of it; but it may be false: and the theory of energy\nwhich assumes the minimum of possible hypotheses would yet be true.\n\n_It contains a great many other Principles._\u2014The principle of the\nconservation of energy contains a large number of the most general\nprinciples of science. It may be shown without much difficulty that,\nfor example, it contains the principle of the inertia of matter, laid\ndown by Galileo and Descartes; that of the equality of action and\nreaction, due to Newton; and even that of the conservation of matter,\nor rather of mass, due to Lavoisier. And finally, it contains the\nexperimental law of equivalence connected with the name of the English\nphysicist Joule, from which may be derived the Law of Hess and the\nprinciple of the initial and final states which we owe to Berthelot.\n\n_It involves the Law of Equivalence._\u2014Here we may be content with\nnoticing that the law of the conservation of energy involves the\nexistence of relations of equivalence between the different varieties.\nA certain quantity of a given energy, measured, as we have seen, by\nthe product of two factors, is equivalent to a certain fixed quantity\nof quite a different form of energy into which it may be converted.\nThe laws which govern energetic transformations therefore contain,\nfrom both the qualitative and the quantitative points of view, all the\nconnections of the phenomena of the universe. To study these laws in\ntheir detail is the task that physics must take upon itself.\n\nThe conversion one into the other of the different forms of energy by\nmeans of equivalents is only a possibility. It is subject, in fact, to\nall sorts of restrictions, of which the most important are due to the\nsecond principle.\n\n\n \u00a7 8. CARNOT\u2019S PRINCIPLE. ITS GENERALITY.\n\n\nThe second fundamental principle is that of the transformations of\nequilibrium, or of the conditions of reversibility, or again, Carnot\u2019s\nprinciple. This principle, which first assumed a concrete form in\nthermodynamics, has been very widely extended. It has reached a degree\nof generality such that contemporary theoretical physicists such as\nLord Kelvin, Le Ch\u00e2telier, etc., consider it the universal law of\nphysical, mechanical, and chemical equilibrium.\n\nCarnot\u2019s principle contains, as was shown by G. Robin, d\u2019Alembert\u2019s\nprinciple of virtual velocities, and according to physicists of\nto-day, as we have just remarked, it contains the laws peculiar to\nphysico-chemical equilibrium. The application of this principle\ngives us the differential equations from which are derived numerical\nrelations between the different energies, or the different modalities\nof universal energy.\n\n_Its Character._\u2014It is very remarkable that we cannot give a general\nenunciation of this principle which by its revealing power has changed\nthe face of physics. This is because it is less a law, properly so\ncalled, than a method or manner of interpreting the relations of the\ndifferent forms of energy, and particularly the relations of heat and\nmechanical energy.\n\n_Conversion of Work into Heat and Vice-vers\u00e2._\u2014The conversion of\nwork into heat is accomplished without difficulty. For example, the\nhammering of a piece of iron on an anvil may bring it to a red heat.\nA shell which passes through an armour plate is heated, and melts and\nvolatilizes the metal all round the hole it has made. By utilizing\nmechanical action under the form of friction all energy can be\nconverted into heat.\n\nThe inverse transformation of heat into work, on the contrary, cannot\nbe complete. The best motor that we can think of, and _\u00e0 fortiori_ the\nbest we can realize, can only transform a third or a fourth of the heat\nwith which it is supplied.\n\nThis is an extremely important fact. It is of incalculable importance\nto natural philosophy, and may be ranked among the greatest discoveries.\n\n_Higher and Degraded Forms of Energy._\u2014Of these we may give an account\nby distinguishing among the forms of universal energy _higher forms_,\nand _lower_ or _degraded forms_. Here we have the principle of the\n_degradation of energy_ on its trial, and it may be regarded as a\nparticular aspect of the second principle of energetics, or Carnot\u2019s\nprinciple. Mechanical energy is a higher form. Thermal energy is\na lower form, a degraded form, and one which has degrees in its\ndegradation. Higher energy, in general, may be completely converted\ninto lower energy; for example, work into heat: the slope is easy to\ndescend, but it is difficult to retrace our steps; lower energy can be\nonly partially transformed into higher energy, and the fraction thus\nutilizable depends upon certain conditions on which Carnot\u2019s principle\nhas thrown considerable light.\n\nThus, although in theory the thermal energy of a body may have its\nequivalent in mechanical energy, the complete transformation is only\nrealizable from the latter to the former, and not from the former to\nthe latter. This is due to a condition of thermal energy which is\ncalled _temperature_. The same quantity of thermal energy, of heat,\nmay be stored in the same thermal body at different temperatures. If\nthis quantity of thermal energy is in a very hot body we can utilize\na large portion of it; if it is in a relatively cold body we can only\nconvert a small portion of it into mechanical work. Thus the value of\nenergy,\u2014_i.e._, its capacity of being converted into a higher and more\nuseful form,\u2014depends on temperature.\n\n_The Capacity of Conversion depends on Temperature._\u2014The conversion\nof heat into work assumes two bodies of different temperatures, the\none warm and the other cold; a boiler and a condenser. Every thermal\nmachine conveys a certain amount of heat from the boiler to the\ncondenser, and what is not thus carried is changed into work. This\nresidue is only a small fraction, a quarter, or at most a third of the\nheat employed, and that, too, in the theoretically perfect machine, in\nthe ideal machine.\n\nThis output, this utilizable fraction depends on the fall of\ntemperature from the higher to the lower level, just as the work of a\nturbine depends on the height of the waterfall which passes through it.\nBut it also depends on the conditions of this fall, on the accessory\nlosses from radiation and conduction. However, Carnot has shown that\nthe output is the same, and a maximum for the same fall of temperature,\nwhatever be the working agent (steam, hot air, etc.), and whatever be\nthe machine\u2014provided that this agent, this substance which works is not\nexposed to accessory losses, that it is never in contact with a body\nhaving temperature different to its own\u2014or again, that it is connected\nonly with bodies impermeable to heat.\n\nThis is Carnot\u2019s principle in one of its concrete forms.\n\nA machine which realizes this condition, that the agent (steam,\nalcohol, ether) is in relation, at all phases of its function, with\nbodies which can neither take heat from it nor give heat to it, is a\n_reversible machine_. Such a machine is perfect. The fraction of heat\nthat it transforms into motion is constant; it is a maximum; it is\nindependent of the motor, of its organs, of the agent: it accurately\nexpresses the transformability of the heat agent into a mechanical\nagent under the given conditions.\n\n_The Degradation and Restoration of Energy._\u2014The fraction not utilized,\nthat which is carried to the condenser at a lower temperature, is\n_degraded_. It can only be used by a new agent, in a new machine in\nwhich the boiler has exactly the same temperature as the condenser in\nthe first machine, and the new condenser has a lower temperature, and\nso on. The proportion of utilizable energy thus goes on diminishing.\nIts utilization requires conditions more and more difficult to\nrealize. The thermal energy loses its potential and its value, and is\nfurther and further degraded as its temperature approaches that of the\nsurrounding medium.\n\nThe degraded energy, theoretically, has kept its equivalent value but,\npractically, it is incapable of conversion. However, it is shown in\nphysics that it can be raised and re-established at its initial level.\nBut for that purpose another energy must be utilized and degraded for\nits benefit.\n\n_The End of the Universe._\u2014What we have just seen with respect to\nheat and motion is to some degree true of all other forms of energy,\nas Lord Kelvin has shown. The principle of the degradation of energy\nis very general. Every manifestation of nature is an energetic\ntransformation. In each of these transformations there is a degradation\nof energy\u2014_i.e._, a certain fraction is lowered and becomes less easily\ntransformable. So that the energy of the universe is more and more\ndegraded; the higher forms are lowered to the thermal form, the latter\nincreasing at temperatures which become more and more uniform. The\nend of the universe, from this point of view, would then be unity of\n(thermal) energy in uniformity of temperature.\n\n_Importance of the Idea of Energy in Physiology._\u2014I have said that the\napplication of Carnot\u2019s principle furnished numerical relations between\nthe different energetic transformations.\n\nThe science of living beings has not yet reached that point of\ndevelopment at which it is possible for us to obtain its numerical\nrelations. However, the consideration of energy and the principle of\nconservation has altered the outlook of physiology on many questions\nwhich are of the highest importance.\n\nThe determination of the sources from which plants and animals draw\ntheir vital energies; the mediate transformation of chemical energy\ninto animal heat in nutrition, or into motion in muscular contraction;\nthe chemical evolution of foods; the study of soluble ferments\u2014all\nthese questions are of considerable importance when we wish to\nunderstand the mechanisms of life. They are therefore departments of\nphysiological energetics in which great advances have already been\nmade.\n\n\n\n\n CHAPTER II.\n\n ENERGY IN BIOLOGY.\n\n \u00a7 1. Energy in Living Beings.\u2014\u00a7 2. The First Law of Biological\n Energetics:\u2014All Vital Phenomena are Energetic Transformations.\u2014\u00a7\n 3. Second Law:\u2014The Origin of Vital Energy is in Chemical Energy.\n Functional Activity and Destruction.\u2014\u00a7 4. Third Law:\u2014The Final Form of\n Energetic Transformation in the Animal is Thermal Energy. Heat is an\n Excretum.\n\n\nThe theory of energy was thought of and utilized in physiology before\nit was introduced into physics, in which it has exercised such an\nextraordinary influence. Robert Mayer was a physicist and a doctor.\nHelmholtz was equally at home in physiology and in physics. From\nthe outset both had seen in this new idea a powerful instrument of\nphysiological research. The volume in which Robert Mayer expounded,\nin 1845, his remarkable views on organic movement in relation to\nnutrition, and Helmholtz\u2019 commentary leave us in no doubt in this\nrespect. The essay on the mechanical equivalent of heat, of a more\nparticularly physical character, is six years later than the earlier\nwork.\n\n_The Relations between Energetics and Biology._\u2014The theory of energy is\ntherefore only returning to its cradle; and to that cradle it returns\nwith all the sanction of physical proof, as the most general theory\never proposed in natural philosophy, and the theory least encumbered\nwith hypotheses. It reduces all particular laws to two fundamental\nprinciples\u2014that of the conservation of energy, which contains the\nprinciples of Galileo and Descartes, of Newton, of Lavoisier, Joule\u2019s\nlaw, Hess\u2019s law, and Berthelot\u2019s principle of the initial and final\nstates; and also Carnot\u2019s principle, from which are deduced the laws\nof physico-chemical and chemical equilibrium. These two principles\ntherefore sum up the whole of natural science. They express the\nnecessary relation of all the phenomena of the universe, their\nuninterrupted gentic connection, and their continuity.\n\n_A priori_ there would be little likelihood that a doctrine, so\nuniversal and so thoroughly verified in the physical world, could be\nrestricted, and thus be useless to the living world. Such a supposition\nwould be contrary to the scientific method, which always tends to the\ngeneralization and the explanation of elementary laws. The human mind\nhas always proceeded thus: it has applied to the unknown order of\nliving phenomena the most general laws of contemporary physics.\n\nThis application has been found legitimate, and has been justified by\nexperiment whenever it has been a question of the laws or of the really\nfundamental or elementary conditions of phenomena. It has, on the other\nhand, however, been unfortunate when it has stopped short of secondary\ncharacteristics. When we now concede the subjection of living beings\nto these general laws of energetics, we are following a traditional\nmethod. There is no doubt that this application is legitimate, and that\nexperiment will justify it _a posteriori_.\n\nI will therefore grant, as a provisional _postulate_, the consequences\nof which will have to be ultimately justified, that the living and\ninanimate world alike show us nothing but _transformations of matter_\nand _transformations of energy_. The word phenomenon will have no\nother signification, whatever be the circumstances under which the\nphenomenon occurs. The varied manifestations which translate the\nactivity of living beings thus correspond to transformations of energy,\nto conversions of one form into another, in conformity with the rules\nof equivalence laid down by the physicists. This conception may be\nformulated in the following manner:\u2014_The phenomena of life have the\nsame claim to be energetic metamorphoses as the other phenomena of\nnature_.\n\nThis postulate is the foundation of biological energetics. It may be\nuseful to give some explanation relative to the signification, the\norigin, and the scope of this statement.\n\nBiological energetics is nothing but general physiology reduced to the\nprinciples that are common to all the physical sciences. Robert Mayer\nand Helmholtz gave the best description of this science, and laid\ndown its limits by defining it as \u201cthe study of the phenomena of life\nregarded from the point of view of energy.\u201d\n\n\n \u00a7 1. ENERGY AT PLAY IN LIVING BEINGS. COMMON OR PHYSICAL ENERGIES.\n VITAL ENERGIES.\n\n\nOur first object will be to define and to enumerate the energies\nat play in living beings; to determine their more or less easy\ntransformations from one to another, to bring to light the general\nlaws which govern those transformations, and finally to apply them to\nthe detailed study of phenomena. This programme may be divided into\nfour parts.\n\nIn the physical world the specific forms of energy are not numerous.\nWhen we have mentioned mechanical, chemical, radiant (thermal and\nphotic) energies, electrical energy, with which is blended magnetic\nenergy, we have exhausted the catalogue of natural agents.\n\nBut is this list for ever closed? Are vital energies comprised in this\nlist? These are the first questions which we must ask ourselves.\n\nThe iatro-mechanical school, on _a priori_ grounds give an affirmative\nanswer. No doubt there are in the living organism many manifestations\nwhich are pure physical manifestations of known energies, mechanical,\nchemical, thermal, etc. But are all the manifestations of the living\nbeing of this order? Are they all, henceforth, reducible to the\ncategories and varieties of energy which are investigated in physics?\nThis is the claim of the mechanical school. But the claim is rash. Our\nfundamental postulate affirms, in principle, that universal energy is\nmanifested in living beings; but, as a matter of fact, there is no\nreason for the assertion that it does not assume particular forms,\naccording to the circumstances peculiar to the conditions under which\nthey are produced.\n\nThese _special forms of energy_ manifested in the conditions suitable\nto living beings would swell the list drawn up by the physicists. And\nit would not be the first instance of an extension of this kind. The\nhistory of science records many remarkable cases. Scarcely a century\nhas passed since we first heard of electrical energy. This discovery\nin the world of energy, which took place, so to speak, before our very\neyes, of an agent which plays so large a part in nature, clearly leaves\nthe door open to other surprises.\n\nWe shall therefore concede that there may be other forms of energy\nat work in living beings than those we already know in the physical\nworld. This reservation would enable us to discover at once the\nessential characteristics by which vital phenomena are henceforth\nreduced to universal physics, and the purely formal differences still\ndistinguishing them.\n\nIf there are really special energies in living beings, our monistic\npostulate leads us to assert that these energies are homogeneous with\nthe others, and that they do not differ from them more than they differ\namong themselves. It is probable that some day they will be discovered\nexternal to living bodies, if the material conditions (which it is\nalways possible to imagine) are realized externally to them. And if we\nmust admit that the peculiarity of the medium is such that these forms\nmust remain indefinitely peculiar to living beings, we may assert with\nevery confidence that these special energies do not obey special laws.\nThey are subject to the two fundamental principles of Robert Mayer\nand Carnot. They are exchanged according to fixed laws with the other\nphysical forms of energies at present known.\n\nTo sum up, then, we must establish three categories in the forms of\nenergy which express the phenomena of vitality.\n\nIn the first place, most of these energies are those which have\nalready been studied and recognized in general physics. They are\nthe same energies: chemical, thermal, mechanical, with their\ncharacteristics of mutability, their lists of equivalents, and their\nactual and potential stales.\n\nIn the second place, it may happen, and it probably will happen, as it\nhappened in the last century in the case of electricity, that some new\nform of energy will be discovered belonging to the universal order as\nto the living order. This will be a conquest of general physics as well\nas of biology.\n\nAnd finally we may rigorously and provisionally admit a last category\nof _vital energies properly so called_.\n\nIt is difficult to give much precision to the idea of _vital energies\nproperly so called_.\n\nIt will be easier to measure them by means of equivalents than to\nindicate their nature. Besides, this is the ordinary rule in the case\nof physical agents. We can measure them, although we know not what they\nare.\n\n_Characteristics of Vital Energies._\u2014We see why we cannot exhibit\nwith precision, _a priori_, the nature of vital energies. In the\nfirst place, they are expressed by what takes place in the tissues\nin activity, and this cannot at present be identified with the known\ntypes of physical, chemical, and mechanical phenomena. This is a first,\nintrinsic reason for not being able to distinguish them readily, since\nwhat takes place is not distinguished by the phenomenal appearances to\nwhich we are accustomed.\n\nThere is a second, intrinsic reason. These vital phenomena are\nintermediary, as we shall see, between manifestations of known\nenergies. They lie between a chemical phenomenon which always precedes\nthem, and a thermal phenomenon which always follows them. They are\nlost sight of, as it were, between manifestations which strike our\nattention. Generally speaking, intermediary energies often escape us\neven in physics. Only the extreme manifestations are clearly seen.\nIn the presence of the organism we are, as it were, in electric\nlighting works which are run by a fall of water, and at first we only\nsee the mechanical energy of the falling water, of the turbine and\ndynamo at work, and the photic energy of the lamps which give the\nlight. Electrical energy, an intermediary, which has only a transient\nexistence, does not impose itself on our attention.\n\nAnd so _vital energies_ for this twofold reason, intrinsic and\nextrinsic, are not readily apparent. To reveal them, the careful\nanalysis of the physiologists is required. They are acts, in most\ncases silent and invisible, which we should scarcely recognize but\nby their effects, after they have terminated in familiar, phenomenal\nforms. This is, for example, what goes on in the muscle in process of\nshortening, in the nerve carrying the nervous influx, in the secreting\ngland. And this is what constitutes the different forms of energy\nwhich we call _vital properties_. M. Chauveau and M. Laulani\u00e9 use\nthe phrase _physiological work_ to distinguish them. _Vital energy_\nwould be preferable. It better expresses the analogy of this special\nform with the other forms of universal energy; it helps us better to\nunderstand that we must henceforth consider it as exchangeable by means\nof equivalents with the energies of the physical world just as they are\nexchangeable one with another.\n\n\n \u00a7 2. FIRST LAW OF BIOLOGICAL ENERGETICS.\n\n\nIt is easy to understand, after these remarks, the significance and\nthe scope of this assertion which contains the first principle of\nbiological energetics\u2014namely, that the phenomena of life have the same\nclaim to be called energetic metamorphoses as the other phenomena of\nnature.\n\n_Irreversibility of Vital Energies._\u2014However, there is one\ncharacteristic of vital energies which deserves the closest attention.\nTheir transformations have a direction which is in some measure\ninevitable. They descend a slope which they never re-ascend. They\nappear to be irreversible. Ostwald has rightly insisted on this\nfundamental characteristic, which no doubt is not that of all the\nphenomena of the living being without exception, but which is certainly\nthat of the most essential phenomena. There are reversible phenomena\nin organisms; there are energetic transformations which may take\nplace from one form of energy to another, or _vice vers\u00e2_. But the\nmost characteristic phenomena of vitality do not act in this way. We\nshall presently see that most functional physiological acts begin\nwith chemical and end with thermal action. The series of energetic\ntransformations takes place in an inevitable direction, from chemical\nto thermal energy. The order of succession of ordinary energies is\nthus determined in the machine of the organism, and therefore by\nthe conditions of the machine. The order of transformation of vital\nenergies is still more rigorously regulated, and the phenomena of life\nevolve from childhood to ripened years, and thence to old age, without\na possible return.\n\nThe laws of biological energetics are three in number. First of all,\nthere is the fundamental principle which we have just developed, and\nwhich is, so to speak, laid down _a priori_; and there are two other\nprinciples, those established by experiment and summing-up, as it were,\nthe multitude of known physiological effects. Of these two experimental\nlaws, one refers to the _origin_ and the other to the _termination of\nthe energies developed in living beings_.\n\n\n \u00a7 3. SECOND LAW OF BIOLOGICAL ENERGETICS.\n\n\n_The Origin of Vital Energy._\u2014Vital energies have their origin in one\nof the _external or common energies_\u2014not in any one we choose, as might\nbe supposed, but in one only: chemical energy. The third principle will\nshow us that they terminate in another energy or a few others, also\ncompletely fixed.\n\nIt follows that the phenomena of life must appear to us to be a\ncirculation of energy which, starting from one fixed point in the\nphysical world, returns to that world by a few points, also fixed,\nafter a transient passage through the animal organism.\n\nOr more precisely, it is a transposition from the realm of matter\ninto the world of energy, of the idea of the _vital vortex_ of\nCuvier and the biologists. They defined life by its most constant\nproperty\u2014nutrition. Nutrition was exactly this current of matter which\nthe organism obtains from without by alimentation, and which it throws\nout again by excretion; and the even momentary interruption of which,\nif complete, would be the signal of death. The cycle of energy is the\nexact counterpart of this cycle of matter.\n\nThe second truth taught us by general physiology, a truth which\nphysiology learned from experiment, is enunciated as follows:\u2014_The\nmaintenance of life consumes none of its energy. It borrows from the\nexternal world all the energy which it expends, and borrows it in the\nform of potential chemical energy._ This is a translation into the\nlanguage of energetics of the results acquired in animal physiology\nduring the last fifty years. No comment is needed to exhibit the\nimportance of such a truth. It reveals the origin of animal activity.\nIt reveals the source from which proceeds that energy which at some\nmoment of its transformations in the animal organism will be a _vital\nenergy_.\n\nThe _primum movens_ of vital activity is, therefore, according to this\nlaw, the chemical energy stored up in the immediate principles of the\norganism.\n\nLet us try to follow, for a moment, this energy through the organism\nand to specify the circumstances of its transformations.\n\n_Organic Functional Activity, and the Destruction of\nReserve-stuff._\u2014Let us suppose then, for this purpose, that our\nattention is directed to a given limited part of this organism, to\na certain tissue. Let us seize it, so to speak, by observation at a\ngiven moment, and let us make an examination of the functional activity\nstarting from this conventional moment. This functional activity,\nlike all other vital phenomena, will be the result, as we have just\nexplained, of a transformation of the potential chemical energy\ncontained in the materials held in reserve in the tissue. This is our\nfirst perceptible fact. This energy, when disengaged, will furnish to\nthe vital action the means by which it may be prolonged.\n\nThere is, then, a _functional destruction_. There is, at the beginning\nof the functional process, and by a necessary effect of that very\nprocess, a liberation of chemical energy; and that can only take place\nby a decomposition of the immediate principles of the tissue, or, as we\nmay say, by a destruction of organic material. Claude Bernard insisted\non this consideration, that the vital function is accompanied by a\ndestruction of organic material. \u201cWhen a movement is produced, when a\nmuscle is contracted, when volition and sensibility are manifested,\nwhen thought is exercised, when a gland secretes, then the substance\nof the muscles, of the nerves, of the brain, of the glandular tissue,\nis disorganized, is destroyed, and is consumed.\u201d Energetics enables us\nto grasp the deeply-seated reason of this coincidence between chemical\ndestruction and the functional activity, the existence of which Claude\nBernard intuitively suspected. A portion of organic material is\ndecomposed, is chemically simplified, becomes less complex, and loses\nin this kind of descent the chemical energy which it contained in its\npotential state. It is this energy which becomes the very texture of\nthe vital phenomenon.\n\nIt is clear that the reserve of energy thus expended must be replaced,\nbecause the organism remains in equilibrium. Alimentation provides for\nthis.\n\nHow does it provide for it? This is a question which deserves detailed\nexamination. We cannot incidentally treat it in full; we can only\nindicate its main features.\n\n_How the supply of Reserve Stuff is kept up._\u2014We know that food does\nnot directly replace the reserve of energy consumed by the functional\nactivity. It is not its potential chemical energy which replaces,\npurely and simply, the energy brought into play, consumed, or, better\nstill, transformed in the active organ, or tissue. Food as it is\nintroduced, inert food, does not, in fact, take up its place _as it\nis_, without undergoing changes in that organ and that tissue, in order\nto restore the _status quo ante_.\n\nBefore building up the tissue it will have undergone various\nmodifications in the digestive apparatus. It will have also undergone\nchanges in the circulatory apparatus, in the liver, and in the\nvery organ we are considering. It is after all these changes that\nassimilation takes place. It will find its place and will have then\npassed into the state of _reserve_.\n\nThe food digested, modified, and finally incorporated as an integral\npart in the tissue in which it will be expended, is therefore in a new\nstate, differing more or less from its state when it was ingested. It\nis a part of the living tissue in the state of constitutive reserve.\nIts potential chemical energy is not the same as that of the food\nintroduced. It may differ from it very remarkably in consequence of\nsudden alterations.\n\nWe do not know for certain at the expense of what category of foods\nthis or that given organ builds up its reserve stuff. There is a\nbelief, for instance, according to M. Chauveau, that the muscle does\nits work at the expense of the reserve of glycogen which it contains.\nThe potential chemical energy of this substance would be a source of\nmuscular mechanical energy. But we do not know exactly at the expense\nof what foods, albumenoids, fats, or carbohydrates the muscle builds\nup the reserve of _glycogen_ expended during its contraction. It is\nprobable that it builds it up at the expense of each of the three\ncategories after the various more or less simple alterations undergone\nby the materials in the digestive tube, the blood, the liver, or other\norgans.\n\nThis building up of reserve stuff, the complement and counterpart of\n_functional destruction_, is not chemical synthesis. It is, on the\ncontrary, generally, and on the whole, a simplification of the food\nthat has been introduced. This is true, at least as far as the muscle\nis concerned. However, to this operation, Claude Bernard has given the\nname of _organizing synthesis_, but the phrase is not a happy one. But\nin no case was the eminent physiologist deceived as to the character of\nthe operation. \u201cThe organizing synthesis,\u201d says he, \u201cremains internal,\nsilent, hidden in its phenomenal expression, gathering together\nnoiselessly the materials which will be expended.\u201d\n\nThese considerations enable us to understand the existence of the\ntwo great categories into which the eminent physiologist divides\nthe phenomena of animal life: the phenomena of the _destruction of\nreserve-stuff_ corresponding to _functional facts_\u2014that is to say\nexpenditures of energy; and the _plastic phenomena_ of the _building-up\nof reserves_ of organic regeneration, corresponding to _functional\nrepose_\u2014_i.e._, to the supply of food to the tissues.\n\n_Distinction between Active Protoplasm and Reserve-stuff._\u2014If it is not\nexactly in these terms that Claude Bernard formulated this fruitful\nidea, it is at any rate in this way that it is to be interpreted.\nThis can be done by giving it a little more precision. We apply\nmore rigorously than that great physiologist the distinction drawn\nby himself between _really active and living protoplasm_ and the\n_reserve-stuff_ which it prepares. To the latter is restricted the\ndestruction by the functional activity and the building up by repose.\n\nThe classification of Claude Bernard is strictly true for\nreserve-stuff. It is easy to criticize the wavering and, as it were,\ndimly groping expressions in which the celebrated physiologist has\nshrouded his ideas. The old adage will excuse him: _Obscuritate rerum\nverba obscurantur_. In the depths of his ignorance he had a flash\nof genius; perhaps he did not find the definitive and, as it were,\nclearly-cut formula defining what was in his mind. But, in this\nrespect, he has left his successors an easy task.\n\n_The Law of Functional Assimilation._\u2014The progress of physiological\nknowledge compels us therefore to distinguish in the constitution of\nanatomical elements two parts\u2014the materials of _reserve-stuff_ and the\n_really active_ and _living protoplasm_. We have just seen how the\nreserve-stuff behaves, alternately destroyed by functional activity,\nand built up afterwards by the ingestion of food, followed by the\noperations of digestion, elaboration, and assimilation. It remains to\nask how this really living and protoplasmic matter behaves. Does it\nfollow the same law? Is it destroyed during the functional activity,\nand is it afterwards replaced? As to this we can express no opinion.\nM. le Dantec fills a gap in our knowledge, in this respect, by an\nhypothesis. He assumes that this essentially active matter grows during\nfunctional activity, and is destroyed during repose. This is what\nhe calls the _law of functional assimilation_. The protoplasm would\ntherefore behave in an exactly contrary manner to the reserve-stuff.\nIt will be its counterpart. But this is only an hypothesis which, in\nthe present state of our knowledge, cannot be verified by experiment\nWe are at liberty to assert either that the protoplasm increases by\nfunctional activity or that it is destroyed. Neither the arguments nor\nthe objections pro or con have any decisive value. The facts alleged on\neither side are capable of too many interpretations.[10]\n\n [10] The reason is to be found in the large number of indeterminates\n in the problem we have to solve. It will be sufficient to enumerate\n them: the two substances which exist in the anatomical element,\n protoplasm and reserve-stuff, to which are attributed contrary roles;\n the two conditions attributable to the protoplasm, of manifested or\n latent activity; the faculty possessed by both of being prolonged for\n an indeterminate period, and of encroaching each on its protagonist\n when its existence is at stake. Here are more elements than are\n necessary to explain the positive or negative results of all the\n experiments in the world.\n\nThe only favourable argument (not demonstrative) is furnished by\nenergetics. It is this. The _re-building of the protoplasm_ is not\nlike the _organisation of reserve-stuff_, a slightly complicated or\neven simplified phenomenon, as happens in the case of the reserve of\nmuscular glycogen. The glycogen, in fact, is built up at the expense\nof foods chemically more complex. It is, on the contrary, a clearly\nsynthetic phenomenon, certainly of chemical complexity, since it ends\nin building up the active protoplasm which is, in some measure, of\nthe highest scale of complexity. Its formation at the expense of the\nsimplest alimentary materials requires, therefore, an appreciable\nquantity of energy.\n\nThe assimilation which organizes the active protoplasm therefore\nrequires energy for its realization. Now, at the moment of functional\nactivity, and by a necessary consequence thereof, the chemical\ndestruction or simplification of the substance of reserve takes place.\nHere is something that meets the case, and we may note the coincidence.\nIt does not mean that the disposable energy is really used to increase\nthe protoplasm, nor that the protoplasm itself is thereby increased.\nIt merely signifies that the wherewithal exists to provide for that\nincrease if it takes place.\n\nIt is therefore _possible_ that the active protoplasm follows the law\nof functional assimilation; but it is _certain_ that the reserve-stuff\nfollows the law laid down by Claude Bernard.\n\nAll these considerations definitely result in the confirmation of this\nsecond law of general physiology, according to which all vital energies\nare borrowed from the potential chemical energy of the reserve-stuff of\nalimentary origin.\n\n\n \u00a7 4. THE THIRD LAW OF BIOLOGICAL ENERGETICS.\n\n\nThe third law of biological energetics is also drawn from experiment.\nIt relates no longer to the point of departure of the cycle of animal\nenergy, but to its final position. _The energetic transformations of\nthe animal end in thermal energy._\n\nThis is the most novel part of the theory, and, if we may say so, that\nleast understood by physiologists themselves. The energy resulting\nfrom the chemical potential of food, having passed through the\norganism (or simply through the organ which we are considering in\naction), and having given rise to phenomenal appearances more or less\ndiversified, more or less dim or clear, obscure or obvious, which are\nthe characteristic or still irreducible manifestations of vitality,\nfinally returns to the physical world. This return takes place (with\ncertain exceptions which will be presently indicated) under the\nultimate form of thermal energy. This we are taught by experiment. The\nphenomena of functional activity are exothermal.\n\nReal vital phenomena thus lie between the chemical energy which gives\nrise to them, and the thermal phenomena to which they in their turn\ngive rise. The place of the vital fact in the cycle of universal energy\nis therefore completely determined. This conclusion is of the utmost\nimportance to biology. It may be expressed in a concise formula which\nsums up in a few words all that natural philosophy can teach as to\nenergetics applied to living beings. \u201cVital energy is a transformation\nof chemical energy into thermal energy.\u201d\n\n_Exceptions._\u2014There are some exceptions to the rigour of this\nstatement, but they are not many in number. We must first of all remark\nthat it applies to _animal life_ alone.\n\nIn the case of vegetables, looked at as a whole, the law must be\nmodified. Their vital energy has another origin, and another final\nform. Instead of being the destroyers of chemical potential energy,\nthey are its creators. They build up by means of the inert and simple\nmaterials afforded them by the atmosphere and the soil, the immediate\nprinciples by which their cells are filled. Their vital functional\nactivity forms by synthesis of the reserves, carbo-hydrates (sugars and\nstarches), fats, albuminoid nitrogenous materials\u2014that is to say, the\nsame three principal categories of foods as those used by animals.\n\nAnd to return to the latter, it should be observed that thermal energy\nis not the only final form of vital energy, as this dogmatic statement\nwould have it supposed. It is only the principle of the final forms.\nThe cycle of energy occasionally terminates in mechanical energy\n(phenomena of motion) and in a less degree in other energies; such\nas, for example, the electrical energy produced by the functional\nactivity of the nerves and muscles in all animals, or in the functional\nactivity of special organs in rays, torpedo-fish, and the malapterurus\nelectricus, or finally, in the photic energy of phosphorescent animals.\nBut these are secondary facts.\n\n_Heat is an Excretum._-The third principle of biological energetics\nmay be therefore thus enunciated:\u2014_Vital energy in its final form\nbecomes thermal energy._ This principle teaches us that if chemical\nenergy is the primitive generating form of vital energies, thermal\nenergy is the form of waste, of emunctory, the degraded form as the\nphysicists would say. Heat is in the dynamical order an excretion of\nanimal life, as urea, carbonic acid and water, are excreta in the\nsubstantial order. By a false interpretation of the principle of the\nmechanical equivalence of heat, or through ignorance of Carnot\u2019s\nprinciple, certain physiologists have fallen into error when they\nstill speak of the transformation of heat into motion or into into\nelectricity in the animal organism. Heat is transformed into nothing\nin the animal organism. It is dissipated. Its utility arises not from\nits energetic value, but from the part it plays as a primer in the\nchemical reactions, as has been explained with reference to the general\ncharacteristics of chemical energy.\n\n_The Effect of Energetics on our Knowledge of the Relations of\nthe Universe._\u2014The consequences of these principles of energetic\nphysiology, which give us so much and which are so clear, are of the\ngreatest importance from the practical as well as from the theoretical\npoint of view.\n\nIn the first place, they show us the position and the rank of the\nphenomena of life in the universe as a whole. They throw fresh light on\nthe noble harmony of the animal and vegetable kingdoms which Priestley,\nIngenhousz, Senebier, and the chemical school of the beginning of the\nnineteenth century discovered, and which was expounded by Dumas with\nincomparable lucidity and brilliance. Energetics is expressed in a\nline. \u201cThe animal world expends the energy accumulated by the vegetable\nworld.\u201d It extends these views beyond the living kingdoms. It shows how\nthe vegetable world itself draws its activity from the energy radiated\nby the sun, and how animals restore it again, in dissipated heat,\nto the cosmic medium. It extends the harmony of the two kingdoms to\nthe whole of nature. The new science makes of the whole universe one\nconnected system.\n\nFrom a more limited point of view, and so that we may not restrict\nourselves to a consideration of the domain of animal physiology,\nthe laws of energetics sum up and explain a multitude of facts and\nof experimental laws\u2014for example, the law of the intermittence of\nphysiological activity, the facts of fatigue, the r\u00f4le and the general\nprinciples of alimentation, and the conditions of muscular contraction.\n\n\n\n\n CHAPTER III.\n\n ALIMENTARY ENERGETICS.\n\n Various Problems of Alimentation. \u00a7 1. _Food the source of Energy\n and Matter._ The two forms of Energy afforded by Food\u2014Vital Energy,\n Thermal Energy. Food the source of Heat. The r\u00f4le of Heat.\u2014\u00a7 2.\n _Measure of the output of Energy_\u2014by the Calometric Method\u2014by the\n Chemical Method.\u2014\u00a7 3. The regular type of Food, Biothermogenic, and\n the irregular type, Thermogenic.\u2014\u00a7 4. Food considered as the source\n of Heat. The Law of Surfaces. The limits of Isodynamics.\u2014\u00a7 5. Plastic\n r\u00f4le of Food. Preponderance of Nitrogenous Foods.\n\n\nAmong the problems on which energetics has thrown a vivid light we have\nmentioned alimentation, muscular contraction, and, more general still,\nthe intermittence of vital functional activity. We shall begin with the\nstudy of alimentation.\n\n_The Different Problems of Alimentation._\u2014What is a food? In what does\nalimentation consist? The dictionary of the _Acad\u00e9mie_ will give us\nour first answer. It tells us that the word food is applied to \u201cevery\nkind of matter, whatever may be its nature, which habitually serves\nor may serve for nutrition.\u201d This is very well put, but here again\nwe must know what nutrition is, and that is not a simple matter; in\nfact, it practically means whatever is usually placed on the table in\na civilized and polished society. But it is just the profound reasons\nfor this traditional practice that we are trying to discover.\n\nThe problem of alimentation may be looked at in a thousand ways. It\nis culinary, no doubt, and gastronomic; but it is also economical and\nsocial, agricultural, fiscal, hygienic, medical, and even moral. But\nfirst and foremost, it is physiological. It comprises and assumes the\nknowledge of the general composition of foods, of their transformations\nin the digestive apparatus, and their comparative utility in the\nmaintenance and the sound functional activity of the organism. To\nthis first group of subjects for our discussion are attached others\nrelating to the effects of inanition, of insufficient alimentation, and\nof over-feeding. And in order to throw light on all these aspects of\nthe problem of alimentation, we have to lay bare the most intimate and\ndelicate reactions by which the organism is maintained and recruited,\nand, in the words of a celebrated physiologist, \u201cto penetrate into\nthe kitchen of vital phenomena.\u201d And here neither Apicius, nor\nBrillat-Savarin, nor Berchoux, nor the moralists, nor the economists\nare of any use to us as guides. We must appeal to the scientists, who,\nfollowing the example of Lavoisier, Berzelius, Regnault, and Liebig,\nhave applied to the study of living beings the resources of general\nscience, and have thus founded _chemical biology_.\n\nThis branch of science developed considerably in the second half of\nthe nineteenth century. It has now its methods, its technique, its\nchairs at the universities, its laboratories, and its literature.\nIt has particularly applied itself to the study of the \u201cmaterial\nchanges\u201d or the _metabolism_ of living beings, and with that object in\nview it has done two things. In the first place, it has determined\nthe composition of the constituent materials of the organism; then\nanalyzing qualitatively and quantitatively all that penetrates into\nthat organism in a given time\u2014that is to say, all the alimentary or\nrespiratory ingesta, and all that issues from the organism, _i.e._,\nall the excreta, all the _egesta_,\u2014it has drawn up _nutritive balance\nsheets_, corresponding to the various conditions of life, whether\nnaturally or artificially created. And thus we can determine the\nalimentary r\u00e9gimes which give too much, and which give too little, and\nwhich finally restore equilibrium.\n\nWe do not propose to give a detailed account of this scientific\nmovement. This may be done in monographs. All we wish to indicate\nhere is the most general result of these laborious researches\u2014that is\nto say, the laws and the doctrines which are derived from them, and\nthe theories to which they have given birth. It is by this alone that\nthey are brought into relation with general science, and may therefore\ninterest the reader. The facts of detail are never lacking to the\nhistorian; it is more profitable to show the movement of ideas. The\ntheories of alimentation bring into conflict very different conceptions\nof the vital functional activity. And here we find a confused medley of\nopinions on which it is not without interest to endeavour to throw some\nlight.\n\n\n \u00a7 1. FOOD, A SOURCE OF ENERGY AND MATTER.\n\n\n_Definitions of Food._\u2014Before the introduction into physiology of the\nnotion of energy, no one had succeeded in giving an exact idea and a\nprecise definition of food and alimentation. Every physiologist and\nmedical man who attempted it had failed, and this for various reasons.\n\nThe general cause of this failure was that most definitions, popular or\ntechnical, interposed the condition that the food must be introduced\ninto the digestive apparatus. \u201cIt is,\u201d said they, \u201ca substance which\nwhen introduced into the digestive tube undergoes, etc., etc.\u201d\nBut plants draw food from the soil, and they possess no digestive\napparatus; many animals have no intestinal tube; and in the case of\ncertain rotifera, the females possess a digestive apparatus, while the\nmales have none. Nevertheless all animals feed.\n\nOn the other hand, there are other substances than those which use the\ndigestive tract for the purpose of entering the organism, and which are\neminently useful or necessary to the maintenance of life. In particular\nwe may mention oxygen.\n\nThe distinctive feature of food is its _utility_\u2014when conveniently\nintroduced or employed\u2014to the living being. Claude Bernard\u2019s definition\nis this:\u2014A substance taken in the external medium \u201cnecessary for the\nmaintenance of the phenomena of the healthy organism and for the\nreparation of the losses it constantly suffers.\u201d \u201cA substance which\nsupplies an element necessary for the constitution of the organism, or\nwhich _diminishes its disintegration_\u201d (stored-up food); this is the\ndefinition of C. Voit, the German physiologist. M. Duclaux says, in\nhis turn, but in far too general terms, that it is a substance which\ncontributes to assure the sound functional activity of any of the\norgans of the living being. None of these ways of describing food gives\na complete idea.\n\n_Food, the Source of Energy and Matter._\u2014The intervention of the\nnotion of energy enables us more completely to understand the true\nnature of food. We must, in fact, have recourse to the energetic\nconception if we desire to take into account all that the organism\nrequires from food. It not only requires _matter_, but also, and most\nimportant of all, energy.\n\nInvestigators so far concentrated their thoughts exclusively on the\nnecessity of a supply of matter\u2014that is to say, they only looked upon\none side of the problem. The living body presents, at each of its\npoints, an uninterrupted series of disintegrations and reconstitutions,\nthe materials being supplied from without by alimentation, and rejected\nby excretion. Cuvier gave to this unceasing circulation of ambient\nmatter throughout the vital world the name of _vital vortex_, and he\nrightly saw in it the characteristic of nutrition, and the distinctive\nfeature of life.\n\nThis idea of the _cycle of matter_ has been completed in our own\ntime by that of the _cycle of energy_. All the phenomena of the\nuniverse, and therefore those of life, are conceived of as energetic\ntransformations. We now look at them in their relationship instead of\nconsidering them individually as of old. Each has an antecedent and a\nconsequent unity with which it is connected in magnitude by the law of\nequivalents taught us by contemporary physics. And thus we may conceive\nof their succession as the cycle of a kind of indestructible agent,\nwhich changes only apparently, or assumes another form as it passes\nfrom one to the other, but its magnitude remains unaltered. This is\nenergy. Thus, in the living being there is not only a circulation of\nmatter, but also a circulation of energy.\n\nThe most general result of research in physiological chemistry\nfrom the time of Lavoisier down to our own day has been to teach us\nthat _the antecedent of the vital phenomenon is always a chemical\nphenomenon_. The vital energies are derived from the potential chemical\nenergy accumulated in the immediate constituent principles of the\norganism. In the same way _the consequent phenomenon of the vital\nphenomenon is in general a thermal phenomenon_. The final form of vital\nenergy is thermal energy. These three assertions as to the nature, the\norigin, and the final form of vital phenomena constitute the three\nfundamental principles, the three laws, of biological energetics.\n\n_Food, a Source of Heat. It is not qu\u00e2 source of heat that food is\nthe source of vital energy._\u2014The place of vital energy in the cycle\nof universal energy is completely determined. It lies between the\nchemical energy which is its generating form and the thermal energy\nwhich is its form of disappearance, of breakdown, the \u201cdegraded form,\u201d\nas the physicists say. Hence we have a result which can be immediately\napplied in the theory of food\u2014namely, that heat is in the dynamical\norder an excretum of the animal life rejected by the living being,\njust as in the substantial order, urea, carbonic acid and water, are\nthe materials used up and again rejected by it. We therefore must\nnot think of the transformation in the animal organism of heat into\nvital energy, as certain physiologists always do. Nor must we think,\nwith B\u00e9clard, of its transformation into muscular movement; or, as\nothers have maintained, into animal electricity. This is not only\nan error of doctrine but an error of fact. It proceeds from a false\ninterpretation of the principle of the mechanical equivalent of heat\nand a misunderstanding of Carnot\u2019s principle. Thermal energy does not\nrepeat the course of the energetic flux in the animal organism. The\nheat is not transformed into anything. It is simply dissipated.\n\n_The Part played by Animal Heat as a Condition of Physiological\nManifestations._\u2014Does this mean that heat is useless to life in the\nvery beings in which it is most abundantly produced\u2014_i.e._, in man\nand in the warm-blooded vertebrates? So far from this being so, it is\nnecessary to life. But its utility has a peculiar character which must\nneither be misunderstood nor exaggerated. It is not transformed into\nchemical or vital reactions, but merely creates for them a favourable\ncondition.\n\nAccording to the first principle of energetics, for the vital fact\nto be derived from the thermal fact, the heat must be preliminarily\ntransformed into chemical energy, since chemical energy is necessarily\nan antecedent and generating form of vital energy. Now this regressive\ntransformation is impossible according to the current theories of\ngeneral physics. The part played by heat in the act of chemical\ncombination is that of a primer to the reaction. It consists in\nplacing the reacting bodies, by changing their state or by modifying\ntheir temperature, in the condition in which they ought to be for the\nchemical forces to come into play. For example, in the combination of\nhydrogen and oxygen by setting light to an explosive mixture, heat\nonly acts as a primer to the phenomenon, because the two gases which\nare passive at ordinary temperatures, require to be raised to 400\u00b0\nC. before chemical affinity comes into play. And so it is with the\nreactions which go on in the organism. They have a maximum temperature,\nand the part played by animal heat is to furnish them with it.\n\nIt follows that heat intervenes in animal life in two capacities\u2014first\nand foremost as _excretum_, or end of the vital phenomenon, of\n_physiological work_; and on the other hand, as a _condition_ or\n_primer_ of the chemical reactions of the organism; and generally,\nas a favourable condition for the appearance of the physiological\nmanifestations of living matter. Thus, it is not dissipated in sheer\nwaste.\n\nI was led to adopt these views some years ago from certain experiments\non the r\u00f4le played in food by alcohol. I did not then know that they\nhad already been expressed by one of the masters of contemporary\nphysiology, M. A. Chauveau, and that they were related in his mind to\na series of conceptions and of researches of great interest, in the\ndevelopment of which I have since then taken a share.\n\n_Two Forms of Energy supplied to Animals by Food._\u2014To say that food is\nsimultaneously a supply of energy and a supply of matter, is really to\nexpress in a single sentence the fundamental conception of biology, in\nvirtue of which life brings into play no substratum or characteristic\ndynamism. According to this, the living being appears to us as the seat\nof an incessant circulation of matter and energy, starting from the\nexternal world and returning to it. All food is nothing but this matter\nand this energy. All its characteristics, our views as to its r\u00f4le, its\nevolution, all the rules of alimentation are simple consequences of\nthis principle, interpreted by the light of energetics.\n\nAnd first of all, let us ask what forms of energy are afforded by food?\nIt is easy to see that there are two\u2014food is essentially a source of\nchemical energy; and secondarily and accessorily, it is a source of\nheat. Chemical energy is the only energy, according to the second\nlaw of energetics, which may be transformed into vital energy. It is\ntrue at any rate for animals; for in plants it is otherwise. There the\nvital cycle has neither the same point of departure nor the same final\nposition. The circulation of energy does not take place in the same\nmanner.\n\nOn the other hand, and this we are taught by the third law, energy\nbrought into play in vital phenomena is finally liberated and restored\nto the physical world in the form of heat. We have just said that this\nrelease of heat is employed in raising the temperature of the living\nbeing. It is animal heat.\n\nThus there are two forms of energy supplied by food, chemical and\nthermal.\n\nIt must be added that these are not the only forms, but the principal,\nand by far the most important. It is not absolutely true that heat is\nthe only outcome of the vital cycle. It is only so in the subject in\nrepose, contented to live idly without doing external mechanical work,\nwithout lifting a tool or a weight, even that of its own body. And\nagain, speaking in this way, we neglect all the movements and all the\nmechanical work which is done without exercise of the volition, by the\nbeating of the heart and of the arteries, the movements of respiration,\nand the contractions of the digestive tube.\n\nMechanical work is, in fact, another possible termination of the cycle\nof energy. But there is no longer anything necessary or inevitable\nin this, since motion and the use of force are in a certain measure\nsubordinated to the capricious volition of the animal.[11]\n\n [11] There is another reason why the r\u00f4le of mechanical energy,\n compared with that of thermal energy, is reduced, in the partition of\n afferent, alimentary energy\u2014at least, in animals which have not to do\n excessive work. The unit of heat, the Calorie, is equivalent to 425\n units of work\u2014_i.e._, to 425 kilogrammetres. In the animal at rest,\n the number of kilogrammetres representing the different quantities\n of work done is small, the number of corresponding Calories is 425\n times smaller. It becomes almost negligeable in comparison with the\n considerable number of Calories dissipated in the form of heat.\n\nAt other times, again, it is an electrical phenomenon which terminates\nthe vital cycle, and it is, in fact, in this way that things happen\nin the functional activity of the nerves and muscles in all animals,\nand in the functional activity of the electrical organ in fish, such\nas the ray and the torpedo. Finally, the termination may be a photic\nphenomenon, and this is what happens in phosphorescent animals.\n\nIt is idle to diminish the power of these principles by proceeding\nto enumerate the whole of the exceptions to their validity. We know\nperfectly well that there are no absolute principles in nature. Let\nus say, then, that the energy which temporarily animates the living\nbeing is furnished to it by the external world under the exclusive\nform of potential chemical energy; but that, if there is only one door\nof entry, there are two exits. It may return to the external world\nin the principal form of thermal energy and in the accessory form of\nmechanical energy.\n\n\n \u00a7 2. MEASUREMENT OF THE SUPPLY OF ALIMENTARY ENERGY.\n\n\n_Calorimetric Method._\u2014From what has preceded it is clear that if the\nenergetic _flux_ which circulates through the animal emerges, _in\ntoto_, in the state of heat, the measurement of this heat becomes the\nmeasurement of the vital energy itself, for the origin of which we\nmust go back to the food. If the flux is divided into two currents,\nmechanical and thermal, they must both be measured and the sum of their\nvalues taken. If the animal does not produce mechanical work, and all\nends in heat, we have only to capture, by means of a calorimeter,\nthis energetic flux as it emerges, and thus measure in magnitude and\nnumerically the energy in motion in the living being. Physiologists use\nfor this purpose various types of apparatus. Lavoisier and Laplace used\nan ice calorimeter\u2014that is to say, a block of ice in which they shut up\na small animal, such as a guinea-pig; they then measured its thermal\nproduction by the quantity of ice it caused to melt. In one of their\nexperiments, for instance, they found that a guinea-pig had melted 341\ngrammes of ice in the space of ten hours, and had therefore set free 27\nCalories.\n\nBut since those days more perfect instruments have been invented.\nM. d\u2019Arsonval employed an air calorimeter, which is nothing but a\ndifferential thermometer very ingeniously arranged, and giving an\nautomatic record. Messrs. Rosenthal, Richet, Hirn and Kaufmann,\nand Lef\u00e8vre have used more or less simplified or complicated air\ncalorimeters. Others, following the example of Dulong and Despretz,\nhave used calorimeters of air and mercury, or with Liebermester,\nWinternitz, and J. Lef\u00e8vre (of Havre), have had recourse to baths.\nHere, then, there is a considerable movement of research which has led\nto the discovery of very interesting facts.\n\n_Measurement of the Supply of Alimentary Energy by the Chemical\nMethod._\u2014We may again reach our result in another way. Instead of\nsurprising the current of energy as it emerges and in the form of\nheat, we may try and capture it at its entry in the form of potential\nchemical energy.\n\nThe evaluation of potential chemical energy may be effected with the\nsame unit of measurement as the preceding\u2014that is to say, the Calorie.\nIf we consider man and mammals, for example, we know that there is\nonly apparently an infinite variety in their foods. We may say that\nthey feed on only three substances. It is a very remarkable fact that\nall the complexity and multiplicity of foods, fruits, grains, leaves,\nanimal tissues, and vegetable products of which use is made, reduce to\nso great a simplicity and uniformity, that all these substances are of\nthree types only: albuminoids, such as albumen or white of egg\u2014foods of\nanimal origin or varieties of albumen; carbo-hydrates, which are more\nor less disguised varieties of sugar; and finally, fats.\n\nHere, then, from the chemical point of view, leaving out certain\nmineral substances, are the principal categories of alimentary\nsubstances. Here, with the oxygen that is brought in by respiration, is\neverything that penetrates the organism.\n\nAnd now, what comes out of the organism? Three things only, water,\ncarbonic acid, and urea. But the former are the products of the\ncombustion of the latter. If we consider an adult organism in perfect\nequilibrium, which varies throughout the experiment neither in\nweight nor in composition, we may say that the receipts balance the\nexpenditure. Albumen, sugar, fat, plus the oxygen brought in, balance\nquantitatively the water, carbonic acid, and urea expelled. Things\nhappen, in fact, as if the foods of the three categories were burned up\nmore or less completely by the oxygen.\n\nIt is this combustion that we have known since the days of Lavoisier\nto be the source of animal heat. We can easily determine the quantity\nof heat left by albumen passing into the state of urea, and by the\nstarch, the sugars, and the fats reduced to the state of water and\ncarbonic acid. This quantity of heat does not depend on the variety\nof the unknown intermediary products which have been formed in the\norganism. Berthelot has shown that this quantity of heat which measures\nthe chemical energy liberated by these substances is identical with\nthe quantity obtained by burning the sugar and the fats in a chemical\napparatus, in a calorimetric bomb, until we get carbonic acid and\nwater, and by burning albumen till we get urea. This result is a\nconsequence of Berthelot\u2019s _principle of initial and final states_.\nThe liberated heat only depends on the initial and final states, and\nnot on the intermediary states. The heat left in the economy by the\nfood being the same as that left in the calorimetric bomb, it is easy\nfor the chemist to determine it. It has thus been discovered that\none gramme of albumen produces 4.8 Calories, one gramme of sugar 4.2\nCalories, and one gramme of fat 9.4 Calories. We thus gather what a\ngiven ration\u2014a mixture in certain proportions of these different kinds\nof foods\u2014supplies to the organism and what energy it gives it, measured\nin Calories.\n\nThe calculation may be carried out to a high degree of accuracy if,\ninstead of confining ourselves to the broad features of the problem, we\nenter into rigorous detail. It is only, in fact, approximately that we\nhave reduced all foods to albumen, sugar, and fat, and all excreta to\nwater, carbonic acid, and urea.\n\nThe reality is a little more complicated. There are varieties of\nalbumen, carbo-hydrates, and fatty bodies, the heats of combustion of\nwhich in the organism oscillate in the neighbourhood of the numbers\n4.8, 4.2, and 9.4. Each of these bodies has been individually examined,\nand numerical tables have been drawn up by Berthelot, Rubner, Stohmann,\nVan Noorden, etc. The tables exhibit the thermal value or energetic\nvalue of very different kinds of foods.\n\nIn our climate, the adult average man, doing no laborious work, daily\nconsumes a maintenance ration composed, as a rule, of 100 grammes of\nalbuminoids, 49 grammes of fats, and 403 grammes of carbo-hydrates.\nThis ration has an energetic value of 2,600 Calories.\n\nIt is therefore, thanks to the victories won in the field of\nthermo-chemistry, and to the principles laid down since 1864 by M.\nBerthelot, that this second method of attack on nutritive dynamism has\nbeen rendered possible. Physiologists, by the aid of these methods,\nhave drawn up _balance-sheets of energy_ for living beings just as they\nhad previously established _balance-sheets of matter_.\n\nNow, it is precisely researches of this kind that we have indicated\nhere as a consequence of biological energetics, which in reality have\nhelped to build up that principle. These researches have shown us\nthat, in conformity with the _principles of thermodynamics_, there\nwas not, in fact, in the organism, any transformation of heat into\nmechanical work, as the physiologists for a short time supposed, on\nthe authority of Berthelot. With the help of our theory this mistake\nis no longer possible. The doctrine of energetics shows us in fact\nthe current of energy dividing itself, as it issues from the living\nbeing, into two divergent branches, the one thermal and the other\nmechanical, external the one to the other although both issuing from\nthe same common trunk, and having between them no relation but this,\nthat the sum of their discharges represents the total of the energy\nin motion. Let us now translate these very simple notions into the\nmore or less barbarous jargon in use in physiology. We shall be\nconvinced as we go on of the truth of the saying of Buffon, that\n\u201cthe language of science is more difficult to learn than the science\nitself.\u201d We shall say, then, that chemical energy, that the unit of\nweight of the food which may be placed in the organism, constitutes\nthe alimentary _potential_, the _energetic value_ of this substance,\nits _dynamogenic power_. It is measured in units of heat, in Calories,\nwhich the substance may leave in the organism. The evaluation is made\naccording to the principles of thermo-chemistry, by means of the\nnumerical tables of Berthelot, Rubner, and Stohmann. The same number\nalso expresses the _thermogenic power_, virtual or theoretical, of the\nalimentary substance. This energy being destined to be transformed\ninto _vital energies_ (Chauveau\u2019s _physiological work_, _physiological\nenergy_), the dynamogenic or thermogenic value of the food is at the\nsame time its biogenetic value. Two weights of different foods which\nsupply the organism with the same number of Calories,\u2014_i.e._ for which\nthese numerical values are the same,\u2014will be called _isodynamic_ or\n_isodynamogenic_, _isobiogenetic_, _isoenergetic_ weights. They will\nbe equivalent from the point of view of their alimentary value. And\nfinally, if, as is usually the case, the cycle of energy ends in the\nproduction of heat, the food which has been utilized for this purpose\nhas a real _thermogenic value_, identical with its theoretical\nthermogenic value. In this case it might be determined experimentally\nby direct calorimetry, measuring the heat produced by the animal\nsupposed absolutely unchanged and identical before and after the\nconsumption of the food.\n\n\n \u00a7 3. DIFFERENT TYPES OF FOODS. THE REGULAR, BIOTHERMOGENIC TYPE AND\n THE IRREGULAR, THERMOGENIC TYPE.\n\n\nFood is a source of thermal energy for the organism because it is\ndecomposed within it, and undergoes within it a chemical degradation.\nPhysiological chemistry tells us that whatever be the manner in which\nit is broken up, it always results in the same body and always sets\nfree the same quantity of heat. But if the point of departure and the\npoint of arrival are the same, it is possible that the path pursued is\nnot constantly identical. For example, one gramme of fat will always\ngive the same quantity of heat, 9.4 Calories, and will always come\nto its final state of carbonic acid and water; but from the fat to\nthe mixture of carbonic acid gas and water there are many different\nintermediaries. In a word we get the conception of varied cycles of\nalimentary evolutions.\n\nFrom the point of view of the heat produced it has just been said that\nthese cycles are equivalent. But are they equivalent from the vital\npoint of view? This is an essential question.\n\nLet us imagine the most ordinary alternative. Food passes from the\nnatural to the final state after being incorporated with the elements\nof the tissues, and after having taken part in the vital operations.\nThe chemical potential only passes into thermal energy after having\npassed through a certain intermediary phase of vital energy. This\nis the normal case, _the regular type of alimentary evolution_. It\nmay be said in this case that the food has fulfilled the whole of\nits function, it has served for the vital functional activity before\nproducing heat. It has been _biothermogenic_.\n\n_The irregular or pure thermogenic type._\u2014And now let us conceive of\nthe most simple _irregular or aberrant type_. Food passes from the\ninitial to the final state without incorporation in the living cells of\nthe organism, and without taking part in the vital functional activity.\nIt remains confined in the blood and the circulating liquids, but it\nundergoes in the end, however, the same molecular disintegration as\nbefore, and sets free the same quantity of heat Its chemical energy\nchanges at once into thermal energy. Food is a _pure thermogen_. It\nhas fulfilled only one part of its work. It has been of slight vital\nutility.\n\nDoes this ever occur in reality? Are there foods which would be only\n_pure thermogens_\u2014that is to say, which would not in reality be\nincorporated with the living anatomical elements, which would form no\npart of them either in a state of provisory constituents of the living\nprotoplasm, or in the state of reserve-stuff; which would remain in the\ninternal medium, in the blood and the lymph, and would there undergo\ntheir chemical evolution? Or again, if the whole of the food does not\nescape assimilation, would it be possible for part to escape it? Would\nit be possible for one part of the same alimentary substance to be\nincorporated, and for the rest to be kept in the blood or the lymph,\nin the circulating liquids _ad limina corporis_, so to speak? In other\nwords, can the same food be according to circumstances a _biothermogen_\nor a _pure thermogen_? Some physiologists\u2014Fick of Wurzburg, for\ninstance\u2014have claimed that this is really the case for most\nnitrogenous elements, carbohydrates, and fats; all would be capable\nof evolving according to the two types. On the other hand, Zuntz and\nvon Mering have absolutely denied the existence of the aberrant or\npure thermogenic type. No substances would be directly decomposed in\nthe organic liquids apart from the functional intervention of the\nhistological elements. Finally, other authors teach that there is a\nsmall number of alimentary substances which thus undergoes direct\ncombustion, and among them is alcohol.\n\n_Liebig\u2019s Superfluous Consumption._\u2014Liebig\u2019s _theory of superfluous\nconsumption_ and Voit\u2019s _theory of the circulating albumen_ assert\nthat the proteid foods undergo partial direct combustion in the\nblood vessels. The organism only incorporates what is necessary for\nphysiological requirements. As for the surplus of the food that is\noffered it, it accepts it, and, so to speak, squanders it; it burns it\ndirectly; and we have a \u201csumptuary\u201d consumption, consumption _de luxe_.\n\nIn this connection arose a celebrated discussion which still divides\nphysiologists. If we disengage the essential body of the discussion\nfrom all that envelops it, we see that it is fundamentally a question\nof deciding whether a food always follows the same evolution whatever\nthe circumstances may be, and particularly when it is introduced in\ngreat excess. Liebig thought that the superabundant part, escaping\nthe ordinary process, was destroyed by direct combustion. He affirmed,\nfor instance, that nitrogenous substances in excess were directly\nburned in the blood instead of passing through their usual cycle of\nvital operations. We might express the same idea by saying that they\nthen undergo an accelerated evolution. Instead of passing through the\nblood in the anatomical element, to return in the dismembered form from\nthe anatomical element to the blood, their breaking up takes place in\nthe blood itself. They save a displacement, and therefore in reality\nremain external to the construction of the living edifice. Their\nenergy, crossing the intermediary vital stage, passes with a leap from\nthe chemical to the thermal form. Liebig\u2019s doctrine reduced to this\nfundamental idea deserved to survive, but mistakes in minor details\ninvolved its ruin.\n\n_Voit\u2019s Circulating Albumen._\u2014A few years later C. Voit, a celebrated\nphysiological chemist of Munich, revived it in a more extravagant form.\nHe held that almost the whole of the albuminoid element is burned\ndirectly in the blood. He interpreted certain experiments on the\nutilization of nitrogenous foods by imagining that these substances\nwhen introduced into the blood were divided as a result of digestion\ninto two parts: the one very small, which was incorporated with the\nliving elements, and passed into the stage of _organized albumen_, the\nother, corresponding to the greater part of the alimentary albumen,\nremained mingled with the blood and lymph, and was subjected in this\nmedium to direct combustion. This was _circulating albumen_. In this\ntheory the tissues are almost stable; the organic liquids alone are\nsubjected to oxydizing transformations, to nutritive metabolism. The\naccelerated evolution, which Liebig considered as an exceptional case,\nwas to C. Voit the rule.\n\n_Current Ideas as to the R\u00f4le of Foods._\u2014The ideas of to-day are not\nthose of Voit; but they do not, however, differ from them essentially.\nWe no longer admit that the greater part of the ingested and digested\nalbumen remains confined in the circulating medium external to the\nanatomical elements. It is held, with Pfl\u00fcger and the school of Bonn,\nthat it penetrates the anatomical element and is incorporated in it;\nbut in agreement with Voit it is believed that a very small part is\nassimilated to the really living matter, to the protoplasm properly\nso called; the greater part is deposited in the cellular element as\nreserve-stuff. The material, properly so called, of the living machine\ndoes not undergo destruction and reparation as extensively as our\npredecessors supposed. There is no need for great reparation. On the\ncontrary, the physiological activity consumes to a great extent the\nreserve-stuff. And the greater part of the food, after having undergone\nsuitable elaboration, serves to replace the reserve-stuff destroyed in\neach anatomical element by the vital functional activity.\n\n_Experimental Facts._\u2014Among the facts which brought physiologists\nof the school of Voit to believe that most foods do not get beyond\nthe internal medium, there is one which may well be mentioned here.\nIt has been observed that the consumption of oxygen in respiration\nincreases notably (about a fifth of its value) immediately after a\nmeal. What does this mean? The interval is too short for the digested\nalimentary substances to have been elaborated and incorporated in the\nliving cells. It is supposed that an appreciable time is required\nfor this complete assimilation. The products of alimentary digestion\nare therefore in all probability still in the blood, and in the\ninterstitial liquids in communication with it. The increase of oxygen\nconsumed would show that a considerable portion of these nutritive\nsubstances absorbed and passed into the blood would be oxydized and\nthen and there destroyed. But this interpretation, however probable\nit may be, does not really fit in with the facts in such a way that\nwe may consider it as proved. Certain experiments by Zuntz and Mering\nare opposed to the idea that combustion in the blood is easy. These\nphysiologists injected certain oxydizable substances into the vessels\nwithout being able to detect any instantaneous oxidation. It is only\nfair to add that against these fruitless attempts other more fortunate\nexperiments may be quoted.\n\n_Category of Purely Thermogenic Foods, with Accelerated Evolution.\nAlcohol. Acids of Fruits._\u2014The accelerated evolution of foods\u2014an\nevolution which takes place in the blood, that is to say outside the\nreally living elements\u2014remains, therefore, very uncertain as far as\nordinary food is concerned. It has been thought that it was a little\nless uncertain as far as the special category of alcohol, acids of\nfruits, and glycerine is concerned.\n\nSome authors consider these bodies as pure thermogens. When alcohol\nis ingested in moderate doses, they say that about a tenth of the\nquantity absorbed becomes fixed in the living tissues; the rest is\n\u201ccirculating alcohol.\u201d It is oxidized directly in the blood and in\nthe lymph, without intervening in the vital functions other than by\nthe heat it produces. From the point of view of the energetic theory\nthese are not real foods, because their potential energy is not\ntransformed into any kind of vital energy, but passes at once to the\nthermal form. On the other hand, other physiologists look upon alcohol\nas really a food. According to them everything is called a food which\nis transformed in the organism with the production of heat; and they\nmeasure the nutritive value of a substance by the number of Calories\nit can give up to the organism. So that alcohol would be a better food\nthan carbohydrated and nitrogenous substances. A definite quantity of\nalcohol, a gramme for instance, is equivalent from the thermal point of\nview to 1.66 grammes of sugar, 1.44 of albumen, or 0.73 of fat. These\nquantities would be _isodynamic_.\n\nExperiment has not entirely decided for or against this theory.\nHowever, the first tests have not been very favourable to it.\nThe researches of C. von Noorden and his pupils, Stammreich and\nMiura, have clearly and directly established that alcohol cannot\nbe substituted in a maintenance ration for an exactly isodynamic\nquantity of carbohydrates. If the substitution is effected, a ration\nonly just capable of maintaining the organism in equilibrium becomes\ninsufficient. The animal decreases in weight. It loses more nitrogenous\nmatter than it can recover from its diet, and this situation cannot be\nsustained for long. On the other hand, the celebrated researches of\nthe American physiologist, Atwater, would plead, on the contrary, in\nfavour of almost isodynamic substitution. Finally, Duclaux has shown\nthat alcohol is a real food, biothermogenic for certain vegetable\norganisms. But urea is also a food for _micrococcus ure\u00e6_. It does not\nfollow that it is a food for mammals. We have not reached the solution\nyet\u2014_adhuc sub judice_.\n\n_Conclusion: The Energetic Character of Food._\u2014To sum up we have\nconfined ourselves, in what has been said, to the consideration of a\nsingle character of food, and really the most essential, its energetic\ncharacter. Food must furnish energy to the organism, and for that\npurpose it is decomposed and broken up within it, and issues from it\nsimplified. It is thus, for instance, that the fats, which from the\nchemical point of view are complicated molecular edifices, escape in\nthe form of carbonic acid and water. And so it is with carbo-hydrates,\nstarchy and sugary substances. This is because these compounds descend\nto a lower degree of complexity during their passage through the\norganism, and by this drop, as it were, they get rid of the chemical\nenergy which they contained in the potential state. Thermo-chemistry\nenables us to deduce from the comparison of the initial and final\nstates the value of the energy absorbed by the living being. This\nenergetic, dynamogenic or thermogenic value, thus gives a measure\nof the alimentary capacity of the substance. A gramme of fat, for\ninstance, gives to the organism a quantity of energy equivalent to 9.4\nCalories; the thermogenic value of the albumenoids is 4.8 Calories.\nThe thermogenic or thermal value of carbohydrates is less than 4.7\ncalories. This being so, we understand why the animal is nourished by\nfoods which are products very high in the scale of chemical complexity.\n\n\n \u00a7 4. FOOD CONSIDERED EXCLUSIVELYY AS SOURCE OF HEAT.\n\n\nWe have seen that food is, in the first place, a source of _chemical\nenergy_; and, in the second place, a source of _vital energy_\u2014finally,\nand consequently, a source of thermal energy. It is this last point\nof view which has exclusively struck the attention of certain\nphysiologists, and hence has arisen a peculiar manner of conceiving the\nr\u00f4le of food. It consists in looking on food as a source of thermal\nenergy.\n\nThis conception is easily applied to warm-blooded animals, but to them\nexclusively\u2014and this is where it first fails. The animal is warmer than\nthe environment in general. It is constantly giving out heat to it. To\nrepair this loss of heat it takes in food in exact proportion to the\nloss it sustains. When it is a question of cold-blooded vertebrates,\nwhich live in water and in most cases have an internal temperature\nwhich is not distinguishable from that of the environment, we see less\nclearly the thermal r\u00f4le of food. It seems then that the production of\nheat is an episodic phenomenon, not existing for itself.\n\nHowever that may be, food is in the second place a source of thermal\nenergy for the organism. Can it be said, inversely, that every\nsubstance which we introduce into the economy, and which is there\nbroken up and gives off heat, is a food? This is a moot point. We dealt\njust now with purely thermogenic foods. However, most physiologists\nare inclined to give a positive answer. In their eyes the idea of food\ncannot be considered apart from the fact of the production of heat.\nThey take the effect for the cause. To these physiologists everything\ningested is called food, if it gives off heat within the body.\n\nTo be heated by food is, indeed, an imperious necessity for the higher\nanimals. If this need be not satisfied the functional activities\nbecome enervated; the animal falls into a state of torpor; and if it\nis capable of attenuated, of more or less latent, life it sleeps in\na state of hibernation; but if it is not capable of this, it dies.\nThe warm-blooded animal with a fixed temperature is so organized that\nthis constancy of temperature is necessary to the exercise and to the\nconservation of life. To maintain this indispensable temperature there\nmust be a continual supply of thermal energy. According to this, the\nnecessity of alimentation is confused with the necessity of a supply\nof heat to cover the deficit which is due to the inevitable cooling\nof the organism. This is the point of view taken up by theorists, and\nwe cannot say that they have no right to do so. We can only protest\nagainst the exaggeration of this principle, and the subordination\nof the other r\u00f4les of food to this single role as a thermogen. It\nis the magnitude of the thermal losses which, according to these\nphysiologists, determines the need for food, and regulates the total\nvalue of the maintenance ration. From the quantitative view it is\napproximately true. From the qualitative point of view it is false.\n\nSuch is the theory opposed to the theory of chemical and vital energy.\nIt has on its side a large number of experts, among whom are Rubner,\nStohmann, and von Noorden. It has been defended in an article in\nthe _Dictionnaire de Physiologie_ by Ch. Richet and Lapicque. They\nhold that thermogenesis absolutely dominates the play of nutritive\nexchanges; and it is the need for the production of heat that\nregulates the total demand for Calories which every organism requires\nfrom its ration. It is not because it produces too much heat that\nthe organism gets rid of it peripherally: it is rather because it\ninevitably disperses it that it is adapted to produce it.\n\n_Rubner\u2019s Experiments._\u2014This conception of the r\u00f4le of alimentation\nis based on two arguments. The first is furnished by Rubner\u2019s last\nexperiment (1893). A dog in a calorimeter is kept alive for a rather\nlong period (two to twelve days); the quantity of heat produced in this\nlapse of time is measured, and it is compared with the heat afforded by\nthe food. In all cases the agreement is remarkable. But is it possible\nthat there should be no such agreement? Clearly no, because there is a\nwell-known regulating mechanism which always exactly proportions the\nlosses and the gains of heat to the necessity of maintaining the fixed\ninternal temperature. This first argument is, therefore, not conclusive.\n\nThe second argument is drawn from what has been called the _law of\nsurfaces_, clearly perceived by Regnault and Reiset in their celebrated\nmemoir in 1849, formulated by Rubner in 1884, and beautifully\ndemonstrated by Ch. Richet. In comparing the maintenance rations\nfor subjects of very different weights, placed under very different\nconditions, it is found that the food always introduces the same\nnumber of Calories for the same extent of skin\u2014_i.e._, for the same\ncooling surface. The numerical data collected by E. Voit show that,\nunder identical conditions, warm-blooded animals daily expend the same\nquantity of heat per unit of surface\u2014namely, 1.036 Calories per square\nyard. The average ration introduces exactly the amount of food which\ngives off sensibly this number of Calories. Now, this is an interesting\nfact, but, like the preceding, it has no demonstrative force.\n\n_Objections. The Limits of Isodynamism._\u2014On the contrary, there are\nserious objections. The thermal value of the nutritive principles only\nrepresents one feature of their physiological r\u00f4le. In fact, animals\nand man are capable of extracting the same profit and the same results\nfrom rations in which one of the foods is replaced by an _isodynamic_\nproportion of the other two\u2014that is to say, a proportion developing the\nsame quantity of heat. But this substitution has very narrow limits.\nIsodynamism\u2014that is to say, the faculty that food has of supplying _pro\nrat\u00e2_ its thermal values\u2014is limited all round by exceptions. In the\nfirst place, there are a few nitrogenous foods that no other nutritive\nprinciple can supply; and besides, beyond this minimum, when the\nsupply takes place, it is not perfect. Lying between the albuminoids\nand the carbohydrates relatively to the fats, it is not between these\ntwo categories relatively to nitrogenous substances if the thermal\npower of food were the only thing that had to be considered in it, the\nisodynamic supply would not fail in a whole category of principles such\nas alcohol, glycerin, and the fatty acids. Finally, if the thermal\npower of a food is the sole measure of its physiological utility,\nwe are compelled to ask why a dose of food may not be replaced by a\ndose of heat. External warming might take the place of the internal\nwarming given by food. We might be ambitious enough to substitute for\nrations of sugar and fat an isodynamic quantity of heat-giving coal,\nand so nourish the man by suitably warming his room. In reality, food\nhas many other offices to fulfill than that of warming the body and\nof giving it energy\u2014that is to say, of providing for the functional\nactivity of the living machine. It must also serve to provide for\nwear and tear. The organism needs a suitable quantity of certain\nfixed principles, organic and mineral. These substances are evidently\nintended to replace those which have been involved in the cycle of\nmatter, and to reconstitute the organic material. To these materials we\nmay give the name of _histogenetic_ foods (repairing the tissues), or\nof _plastic_ foods.\n\n\n \u00a7 5. THE PLASTIC R\u00d4LE OF FOOD.\n\n\n_Opinions of the Early Physiologists._\u2014It is from this point of view\nthat the ancients regarded the r\u00f4le of alimentation. Hippocrates,\nAristotle, and Galen believed in the existence of a unique nutritive\nsubstance, existing in all the infinitely different bodies that man\nand the animals utilize for their nourishment. It was Lavoisier\nwho first had the idea of a dynamogenic or thermal r\u00f4le of foods.\nFinally, the general view of these two species of attributes and their\nmarked distinction is due to J. Liebig, who called them _plastic_ and\n_dynamogenic_ foods. In addition he thought that the same substance\nshould accumulate the same attributes, and that this was the case with\nthe albuminoid foods, which were at once _plastic_ and _dynamogenic_.\n\n_Preponderance of Nitrogenous Foods._\u2014Magendie, in 1836, was the\npioneer who introduced in this interminable list of foods the first\nsimple division. He divided them into proteid substances, still called\nalbuminoids, nitrogenous, quaternary, and _ternary substances_. Proteid\nsubstances are capable of maintaining life. Hence the preponderant\nimportance given by the eminent physiologist to this order of foods.\nThese results have since been verified. Pfl\u00fcger, of Bonn, gave a\nvery convincing proof of this a few years ago. He fed a dog, made it\nwork, and finally fattened it, by giving it nothing at all to eat but\nmeat from which had been extracted, as thoroughly as possible, every\nother substance.[12] The same experiment showed that the organism can\nmanufacture fats and carbo-hydrates at the expense of the nitrogenous\nfood, when it does not find them ready formed in the ration. The\nalbumen will suffice for all the needs of energy and and matter. To\nsum up, there is no necessary fat, no carbohydrate is necessary;\nalbuminoids alone are indispensable. Theoretically, the animal and man\nalike could maintain life by the exclusive use of proteid food; but,\npractically, this is not possible for man, because of the enormous\namount of meat which would have to be used (3 kilogrammes a day).\n\n [12] It is not certain, however, that all the precautions taken\n have the desired result. You cannot entirely deprive meat of its\n carbohydrates.\n\nOrdinary alimentation comprises a mixture of three orders of\nsubstances, and to this mixture albumen brings the plastic element\nmaterially necessary for the reparation of the organism; it also is\nthe source of energy. The two other varieties only bring energy. In\nthis mixed regimen the quantity of albumen must never descend below a\ncertain minimum. The efforts of physiologists of late years have tended\nto fix with precision this minimum ration of albuminoids\u2014or as we may\nbriefly put it, of _albumen_\u2014below which the organism would perish.\nVoit had found 118 grammes of albumen necessary for the average adult\nman weighing 70 kilos. This figure is certainly too high. The Japanese\ndoctors, Mori, Tsubo\u00ef, and Murato, have shown that a considerable\nportion of the population of Japan is content with a diet much poorer\nin nitrogen, and suffers no inconvenience. The Abyssinians, according\nto Lapicque, ingest, on the average, only 67 grammes of albumen per\nday. A Scandinavian physiologist, Siven, experimenting on himself,\nfound that he could reduce the ration of albumen necessary to the\nmaintenance and equilibrium of the organism to the lowest figures\nwhich have been yet reached\u2014namely, from 35 to 46 grammes a day. These\nexperiments, however, must be confirmed and interpreted. Besides, it\nis important to point out that the most advantageous ration of albumen\nrequires to be a good deal above the strictly sufficient quantity.\n\nIt only remains to refer to several other recent researches. The most\nimportant of many are those published by M. Chauveau, on the reciprocal\ntransformation of the immediate principles in the organism according\nto the conditions of its functioning and the circumstances of its\nactivity. To deal with these researches with as much detail as they\ndeserve, we must study the physiology of muscular contraction and of\nmovement\u2014that is to say, of muscular energetics.\n\n\n\n\n BOOK III.\n\n THE CHARACTERS COMMON TO LIVING BEINGS.\n\n Chapter I. Summary: The doctrine of vital unity.\u2014Chapter II. The\n morphological unity of living beings.\u2014Chapter III. The chemical unity\n of living beings.\u2014Chapter IV. The mutability of living beings.\u2014Chapter\n V. The specific form, its acquisition, and reparation.\u2014Chapter VI.\n Nutrition.\n\n\n CHAPTER I.\n\n THE DOCTRINE OF VITAL UNITY.\n\n Phenomena common to all living beings\u2014Theory of vital duality\u2014Unity in\n the formation of immediate principles\u2014Unity in the digestive acts\u2014The\n common vital fund.\n\n\nWhen we ask the various philosophical schools what life is, some show\nus a chemical retort, and others show us a soul. Whether vitalists\nor of the mechanical school, these are the adversaries who since\nphilosophy began have vainly contested the possession of the secret\nof life. We need not concern ourselves with this eternal quarrel. We\nneed not ask Pythagoras, Plato, Aristotle, Hippocrates, Paracelsus,\nVan Helmont, and Stahl what idea they formed of the vital principle;\nnor need we probe to the depths the ideas of living nature held by\nEpicurus, Democritus, Boerhaave, Willis, and Lamettrie; nor need we\napply to the iatromechanicians nor to the chemists. We may do better\nthan that. We may ask nature itself.\n\n_Phenomena Common to Living Beings._\u2014Nature shows us an infinite number\nof beings, animal or vegetable, described in ordinary language as\n_living beings_. This language implicitly assumes something common to\nthem all, a universal manner of being which belongs to them without\ndistinction, without regard to differences of species, types, or\nkingdoms. On the other hand, anatomical analysis teaches us that\nanimated beings and plants may be divided into parts ever decreasing\nin complexity, of which the last and the simplest is the _anatomical\nelement_, the _cell_, the microscopic organic unit which, too, is\nalive. Common opinion suspects that all these beings, whether entire\nas in the case of animal and vegetable individuals, or fragmentary as\nin the case of cellular elements, have the same manner of being, and\npresent the same body of common characteristics which rightly gives\nthem this unmistakable title of living beings. Life then essentially\nwould be this manner of being, common to animals, vegetables, and their\nelements. To seize in isolation these common, necessary, and permanent\nfeatures, and then to synthetize them into a whole, will be the really\nscientific method of defining life, and of explaining its nature.\n\nAnd here then immediately arises a fundamental question which gives\none pause, a question of fact which must be solved before we can\ngo further. Is there really a common manner of being in all these\nthings? Are _animal life, vegetable life_, and the life of the\nelements or _elementary life_, all the same? Is there a sum total of\ncharacteristics which may define life in general?\n\nThe physiologists, following in the steps of Claude Bernard, respond in\nthe affirmative. They accept as valid and convincing the proof given of\nthis vital community by the illustrious experimentalist. However there\nare some rare exceptions to this universal assent. In this concert\nof approval there is at least one discordant voice, that of M. F. Le\nDantec.[13]\n\n [13] M. Le Dantec, of whose philosophical and rigorously systematic\n mind I have the highest opinion, has laid down a new conception of\n life, the essential basis of which is this very distinction between\n elementary life and ordinary life; between the life of the elements\n or of the beings formed from a single cell, protophytes and protozoa,\n and the life of ordinary animals and plants, which are multicellular\n complexes, and for that reason called _metazoa_ and _metaphytes_.\n\n Further, in the _elementary life_ peculiar to monocellular beings\n (protozoa and cellular elements), M. Le Dantec distinguishes three\n manners of being:\u2014The first condition, which is elementary life\n manifested in all its perfection, cellular health; the second\n condition is deteriorated elementary life, _cellular disease_; and the\n third condition, which is _latent life_. I should say at once that in\n so far as the fundamental distinction of the phenomena of _elementary\n life_ and those of the general life of animals and ordinary plants,\n metazoa or metaphytes is concerned, we find it neither justified nor\n useful. And further, _manifested elementary life_, as M. Le Dantec\n understands it, would only belong to a small number of _elementary\n beings_\u2014for the protozoa, starting with the infusoria, are not among\n the number\u2014and to a still smaller number of _anatomical elements_,\n since among the vertebrates we recognize as almost the only elements\n satisfying it, the ovule, and perhaps the leucocyte. Physiologists,\n therefore, do not agree with M. Le Dantec as to the utility of adding\n one condition more to those we all admit\u2014namely, manifested animal\n life and latent life.\n\n_The Doctrine of the Vital Duality of Animals and Plants._\u2014There are,\ntherefore, biologists who, in the domain of theory and in virtue of\nmore or less well-founded conceptions or interpretations, separate\n_elementary life_ from other vital forms, and thus break the bond of\nvital unity proclaimed by Claude Bernard. This monistic doctrine at the\noutset met with other opponents, and that, too, in the domain of facts.\nBut it triumphed over them and became established. We have to deal with\nscientists like J. B. Dumas and Boussingault, who drew a dividing line\nbetween _animal life_ and _vegetable life_.\n\nBut let us in a few words recall to the reader this victorious struggle\nof the monistic doctrine against the dualism of the two kingdoms. If\nwe consider an animal in action, said the champions of vital dualism,\nwe agree that it feels, moves, breathes, digests, and finally, that\nit destroys by a real operation of chemical analysis the materials\nafforded to it by its ambient world. It is in these phenomena that are\nmanifested its activity, its life. Now, added the dualists, plants do\nnot feel, do not move, do not breathe, and do not digest. They build\nup from immediate principles, by an operation of chemical synthesis,\nthe materials they borrow from the soil which bears them, or from the\natmosphere which surrounds them. There is, therefore, nothing in common\nbetween the representatives of the two kingdoms if we confine ourselves\nto the examination of the actual phenomena which take place in them.\nTo find a resemblance between the animal and the vegetable, said the\ndualists, we must set aside what they _do_, for they do different,\nor even contrary things. We must consider whence they come and what\nthey _become_. Both originate in organisms similar to themselves.\nThey grow, evolve, and generate as they themselves were generated.\nIn other words, while their acts separate plants from animals, their\nmode of origin and evolution alone bring them together. Such analogies\nare of no slight importance; but they were neutralized by their\ndissimilarities, which were exaggerated by the dualistic school.\n\nIt is clear that the word _life_ would lose all actual significance to\nthose who would reduce it to the faculty of evolution, and who would\nseparate all its real manifestations in animated beings and in plants.\nIf there are two lives, the one animal and the other vegetable, there\nare no more; or, what comes to the same thing, there is an infinite\nnumber of lives which have nothing in common but the name, or at most,\nthe possession of some secondary characteristics. There are as many of\nthem as there are different beings, for each has its own particular\nevolution. Here the specific is the negation of the general and it\ndestroys it instead of being subordinate to it. The principle of life\nbecomes for each being something as individual as its own evolution.\nAnd this, if we think it out, is how the philosophers look at life,\nand it is the real reason of their disagreement with the physiological\nschool.\n\n_Proof of the Monistic Theory._\u2014On the other hand, under the\ndisguise of living forms, the physiologist recognizes the existence\nof an identical basis. His trained ear marks amid the overcharged\ninstrumentation of the vital work the recognizable undertones of\na constant theme. It was the work of Claude Bernard to bring this\ncommon basis to light. He shows that plants live as animals do, that\nthey breathe, digest, have sensory reactions, move essentially like\nanimals, destroy and build up in the same manner the immediate chemical\nprinciples. For that purpose it was necessary to pass in review,\nexamining them from their foundation and distinguishing the essential\nfrom the secondary, the different vital manifestations\u2014digestion,\nrespiration, sensibility, motility, and nutrition. This is what Claude\nBernard did in his work _Sur les Ph\u00e9nom\u00e8nes de la vie communs aux\nanimaux et aux plantes_. We need only to sketch in broad outline the\ncharacteristic features of his lengthy demonstration.\n\n_Unity in the Formation of Immediate Chemical Principles._\u2014The first\nand most important of the differences pointed out between the life of\nanimals and that of plants was relative to the formation of immediate\nprinciples. On this ground, indeed, vital dualism raised its fortress.\nThe animal kingdom was considered in its totality as the parasite of\nthe vegetable kingdom. To J. B. Dumas, animals, whatever they may be,\nmake neither fat nor any elementary organic matter; they borrow all\ntheir foods, whether they be sugars or starches, fats or nitrogenous\nsubstances, from the vegetable kingdom. About the year 1843 the\nresearches of the chemists, and of Payen in particular, succeeded in\nproving the presence, almost constant, of fatty matters in vegetables;\nand, further, these matters existed there in proportions more than\nsufficient to explain how the beast which fed upon them was fattened.\nThe chemists attributed to nature as much practical sense as they\nthemselves possessed; and since the hay and the grass of the ration\nbrought fat ready made to the horse, the cow, and the sheep, they\ndeclared that the animal organism had nothing whatever to do but to\nput this food into the tissues, or to arrange for it to pass into the\nmilk. But nature is not so wise and economical as was supposed at\nthe Acad\u00e9mie des Sciences. After a memorable debate, in which Dumas,\nBoussingault, Payen, Liebig, Persoz, Chossat, Milne-Edwards, and\nFlourens took part, and, later on, Berthelot and Claude Bernard, it was\nagreed that the animal does not grow fat from the fatty food which is\nsupplied it, and that it makes its own fat just as the vegetable does,\nbut in another manner. In the same way sugar, the normal constituent\nsubstance necessary for the nutrition of animals and plants, instead of\nbeing a vegetable product passing by alimentation from the herbivorous\nanimals and thence to the carnivorous, is manufactured by the animal\nitself. Generally speaking, immediate principles have an equal claim\nto existence in the two kingdoms. Both form and destroy the substances\nindispensable to life.\n\nHere, then, one of the barriers between animal life and vegetable life\nis overthrown and destroyed.\n\n_Unity of Digestive Acts in Animals and Plants._\u2014Similarly, another\nbarrier falls if we show that digestion, long considered the exclusive\nfunction of animals, and, in particular, of the higher animals, is in\nreality universal.\n\nCuvier pointed out the absence of a digestive apparatus as a very\ngeneral and distinctive characteristic of plants. But the absence\nof a digestive apparatus does not necessarily imply the absence of\ndigestion. The essential act of digestion is independent of the\ninfinite variety of the organs, just as a reaction is independent of\nthe form of the vessel in which it takes place. It is, in fact, a\nchemical transformation of an alimentary substance. This transformation\nmay be realized outside the organism, _in vitro_, just as it can in\nthe living being without masticating organs, without an intestinal\napparatus, without glands, in a vessel placed in a stove, simply by\nmeans of a few soluble ferments\u2014pepsine, trypsine, amylolytic diastases.\n\nAll alimentary substances, whether taken from without or borrowed\nfrom the reserves accumulated in the internal stores of the organism,\nmust undergo preparation. This preparation is digestion. Digestion is\nthe prologue of nutrition. It is over when the reparative substance,\nwhether food or reserve-stuff, is brought into a state enabling it to\npass into the blood, and to be utilized by the organism.\n\n_The Identity of Categories of Foods in the Two Kingdoms._\u2014Now the\nalimentary substances are the same in the two kingdoms, and so\nis their digestive preparation. Alimentary materials are of four\nkinds: albuminoid, starchy, fatty, and sugary substances. The animal\ntakes them from without (food properly so-called), or from within\n(reserve-stuff). Man obtains starch, for instance, from different\nfarinaceous dishes. It may, however, equally well be borrowed from\nthe reserve of flour that we carry within us in our liver, which is a\nveritable granary, full of floury substance, glycogen. And so it is\nwith vegetables. The potato has its store of flour in its tuber just as\nthe animal has in its liver. The grain which is about to germinate has\nit in reserve-stuff in its cotyledons, or in its albumen. The bud which\nis about to develop into a tree or a flower carries it at its base.\n\nThe same conclusions are true for another class of substances, the\nsugars. They may be a food taken from without, or a reserve deposited\nin the tissues. The animal takes from without, in fruits for instance,\nthe ordinary sugar which pleases its taste. Beetroot, when flowering\nand fructifying, draws this substance from its roots in which stores\nhave been amassed. The sugar cane when running to seed takes the sugar\nfrom the stores which it possesses in its cane. Brewer\u2019s yeast, the\n_saccharomyces cerevisi\u00e6_, the agent of alcoholic fermentation, finds\nthis same substance in the sugary juices favourable to its development.\n\nIn the same way, identically fatty substances, either in the\nform of food or of reserve-stuff, serve for nutrition to animals\nand vegetables; and that is again true of the substances of the\nfourth class, albuminoids, identical in the two kingdoms, foods or\nreserve-stuff, equally utilizable in both after digestion.\n\n_Identity of the Digestive Agents and Mechanisms in Plants and\nAnimals._\u2014Now, the results of contemporary research have been to\nestablish a surprising resemblance in the modifications experienced\nby these foods, or reserve stuffs, in animals and plants; and even\nresemblances in the agents which realize them, and in the mechanisms by\nwhich they are performed. There is a real unity. The flour accumulated\nin the tuber of the potato is liquefied and digested on the appearance\nof the buds or of the flower, just as the starch of the liver or the\nalimentary flour is digested by the animal. The fatty matter which\nis stored up in the oleaginous grain is digested at the moment of\ngermination, just as the fat during a meal is digested in the animal\u2019s\nintestine. As the beetroot begins to run to seed, the root gives up\npart of its store of sugar, and this reserve stuff is distributed\nthroughout the stalk after having been digested, exactly as would have\nbeen the case in the digestive canal of man.\n\nVegetables, then, really digest. The four classes of substances\nmentioned above are really digested in order to pass from their\nactual form, a form unsuitable for interstitial exchanges, to another\nform suitable for nutrition. As there are four kinds of foods, so\nthere are four kinds of digestions, four kinds of ferment-producing\nagents\u2014amylolytic,[14] proteolytic,[15] saccharine, and lipasic[16]\ndiastases, identical in the animal and the plant. Identity of ferments\nimplies identity of digestions. Going down to the very basis of things,\nthe digestive act is nothing but the action of this ferment. This\nis the crux of the whole question. All else is only difference in\nscene, varying in the means of execution and in the accessories. The\ndifference arises from the stage on which it takes place, but the piece\nwhich is being played is the same, and the actors are the same, and so\nis the action of the play.\n\n [14] Amylolytic ferments change starch and glycogen (_amyloses_) into\n sugar.\u2014TR.\n\n [15] Proteolytic ferments change proteids into peptones and\n proteoses.\u2014TR.\n\n [16] The enzyme known as lipase splits the fat or oil in germinating\n seeds into a fatty acid and glycerine.\u2014TR.\n\nThis identity between animal and vegetable life is found in the\nphenomena of respiration and of motility. The limits of this book do\nnot allow of our entering into the details of facts. Besides, the facts\nare well known, and may be found in any treatise on general physiology.\nThis science, therefore, enables us to perceive the imposing unity of\nlife in its essential manifestations.\n\nThe community of the phenomena of vitality in animals and plants being\nthus placed beyond a doubt, we must now discover the reason why. This\nreason is to be found in their anatomical and in their chemical unity.\nThe fundamental phenomena are common because the composition is common,\nand because the universal anatomical basis, the cell, possesses in all\ncases a sum total of identical properties.\n\nIf we appeal to physiology for the characteristics common to living\nbeings, it will generally give us the following:\u2014A structure or\norganization; a certain chemical composition which is that of _living\nmatter_; a specific form; an evolution which in the earliest stage\noccasions the being to grow and develop until it is divided, and\nwhich in the highest stage includes one or more evolutive cycles\nwith growth, the adult stage, senility, and death; a property of\nincrease or nutrition, with its consequence\u2014namely, a relation of\nmaterial exchanges with the ambient medium;\u2014and finally, a property of\nreproduction. It is important to pass them rapidly in review.\n\n\n\n\n CHAPTER II.\n\n MORPHOLOGICAL UNITY OF LIVING BEINGS.\n\n \u00a7 1. The cellular theory. First period: division of the organism\u2014\u00a7\n 2. Second period: division of the cell\u2014Cytoplasm\u2014The nucleus\u2014\u00a7 3.\n Physical constitution of living matter\u2014The micellar theory\u2014\u00a7 4.\n Individuality of complex beings\u2014The law of the constitution of\n organisms.\n\n\nThe first characteristic of the living beings is _organization_.\nBy that we mean that they have a structure; that they are complex\nbodies formed of smaller aliquot parts and grouped according to a\ncertain disposition. The most simple elementary being is not yet\nhomogeneous. It is heterogeneous. It is organized. The least complex\nprotoplasms, those of bacteria, for example, still possess a physical\nstructure; Kunstler distinguishes in them two non-miscible substances,\npresenting an alveolar organization. Thus animals and plants present an\norganization, and it is sensibly constant from one end to the other of\nthe scale of beings. There is a _morphological unity_.\n\n\n \u00a7 1. THE CELLULAR THEORY. FIRST PERIOD: DIVISION OF THE ORGANISM INTO\n CELLS.\n\n\n_Cellular Theory. First Period._\u2014Morphological unity results from the\nexistence of a universal anatomical basis, the _cell_. The cellular\ntheory sums up the teaching of general anatomy or histology.\n\nAt the beginning of the nineteenth century anatomy was following a\nroutine dating from ancient times. It divided animal and vegetable\nmachines into units in descending order, first into different forms\nof apparatus (circulatory, respiratory, digestive, etc.); then the\napparatus into organs examined one by one, figuring and describing each\nof them from every point of view with scrupulous accuracy and untiring\npatience. If we think of the duration of these researches\u2014the _Iliad_,\nas Malgaigne says, already containing the elements of a very fine\nregional anatomy\u2014and especially of the powerful impulse they received\nin the seventeenth and eighteenth centuries, we shall understand the\nillusion of those who, in the days of X. Bichat, could fancy that the\ntask of anatomy was almost ended.\n\nAs a matter of fact this task was barely begun, for nothing was known\nof the intimate structure of the organs. X. Bichat accomplished a\nrevolution when he decomposed the living body into tissues. His\nsuccessors, advancing a step in the analysis, dissociated the\ntissues into elements. These elements, which one would have thought\nwere infinitely varied, were reduced in their turn to one common\n_prototype_, the cell.\n\nThe living body, disaggregated by the histologist, resolves under the\nmicroscope into a dust, every grain of which is a cell. A cell is an\nanatomical element the constitution of which is the same from one\npart to the other of the same being, and from one being to another;\nand its dimensions, which are sensibly constant throughout the whole\nof the living world, have an average diameter of several thousandths\nof a millimetre\u2014_i.e._, of several _microns_. This element, the cell,\nis a real organ. It is smaller, no doubt, than those described by the\nancient anatomists, but it is not less complex. Its complexity is only\nrevealed later. It is an organic unit. Its form varies from one element\nto another. Its substance is a semi-fluid mass, a mixture of different\nalbuminoids. In the mean value of its dimensions, so carefully\nmeasured\u2014_exceptis excipiendis_\u2014we have a condition the significance of\nwhich has not yet been discovered, but which may be of great value in\nthe explanation of its peculiar activities.\n\nSuch is the result to which have converged the researches of the\nbiologists who have examined plants or the lower animals, as well as\nof the anatomists who have been more especially occupied with the\nvertebrates and with man. All their researches have brought them to the\nsame conclusion\u2014the cellular theory. Either living beings are composed\nof a single cell\u2014as is the case with the microscopic animals called\n_protozoa_, and the microscopic vegetables called _protophytes_\u2014or,\nthey are cellular complexes, _metazoa_ or _metaphytes_\u2014that is to say,\nassociations of these microscopic organic units which are called cells.\n\n_The Law of the Composition of Organisms._\u2014The law of the composition\nof organisms was discovered in 1838 by Schleiden and Schwann. From that\ntime up to 1875 it may be said that micrographers have spent their\ntime in examining every organ and every tissue, muscular, glandular,\nconjunctive, nervous, etc., and in showing that in spite of their\nvarieties of aspect and form, of the complexity of structures due to\ncohesion and fusion, they all resolve into the common element, the\ncell. Contemporary anatomists, Koelliker, Max Schultze, and Ranvier,\nhave thus established the generality of the cellular constitution,\nwhile zoologists and botanists confirm the same law for all animals and\nvegetables, and exhibit them all as either unicellular or multicellular.\n\n_The Cellular Origin of Complex Beings._\u2014At the same time embryogenic\nresearches showed that all beings spring from a corpuscle of the same\ntype. Going back in the history of their development to the most remote\nperiod, we find a cell of very constant constitution\u2014namely, the\n_ovule_. This truth may be expressed by changing a word in Harvey\u2019s\ncelebrated aphorism\u2014_omne vivum ex ovo_; we now say omne _vivum e\ncellula_. The myriads of differentiated anatomical elements whose\nassociation forms complex beings are the posterity of a cell, of the\n_primordial ovule_, unless they are the posterity of another equivalent\ncell. The second task of histology in the latter half of the nineteenth\ncentury consisted in following up the filiation of each anatomical\nelement from the cell-egg to its state of complete development.\n\nThe whole cellular theory is contained in the two following statements,\nwhich establish the morphological unity of living beings:\u2014_Everything\nis a cell, everything comes from an initial cell_; the cell being\ndefined as a mass of substance, protoplasm or protoplasms, of an\naverage diameter of a few microns.\n\n\n \u00a7 2. THE SECOND PERIOD: THE DIVISION OF THE CELL.\n\n\n_Second Period: Constitution of the Cell._\u2014This was, however, only the\nfirst phase in the analytical study of the living being. A second\nperiod began in 1873 with the researches of Strassburger, B\u00fctschli,\nFlemming, Kuppfer, Fromann, Heitzmann, Balbiani, Guignard, Kunstler,\netc. These observers in their turn submitted this anatomical, this\ninfinitely small cellular microcosm, to the same penetrating dissection\ntheir predecessors had applied to the whole organism. They brought\nus down one degree lower into the abyss of the infinitely small. And\nas Pascal, losing himself in these wonders of the imperceptible, saw\nin the body of the mite which is only a point, \u201cparts incomparably\nsmaller, legs with joints, veins in the legs, blood in the veins,\nhumours in the blood, drops in the humours, vapours in these drops,\u201d so\ncontemporary biologists have shown in the epitome of organism called a\ncell, an edifice which itself is marvellously complex.\n\n_The Cytoplasm._\u2014The observers named above revealed to us the extreme\ncomplexity of this organic unit. Their researches have shown us the\nstructure of the two parts of which it is composed\u2014the cellular\nprotoplasm and the nucleus. They have determined the part played by\neach in genetic multiplication. They have shown that the protoplasm\nwhich forms the body of the cell is not homogeneous, as was at first\nsupposed. The idea which was mooted later, that this protoplasm was\nformed, to use Sachs\u2019 words, of a kind of \u201cprotoplasmic mud,\u201d\u2014_i.e._,\nof a dust consisting of grains and granules connected by a liquid,\u2014is\nno longer accurate. There is a much simpler view of the case. According\nto Leydig and his pupils, we must compare the protoplasm to a sponge in\nthe meshes of which is lodged a fluid, transparent, hyaline substance,\na kind of cellular juice, hyaloplasm. From the chemical point of\nview this cellular juice is a mixture of very different materials,\nalbumens, globulins, carbohydrates, and fats, elaborated by the cell\nitself. It is a product of vital activity; it is not yet the seat of\nthis activity. The living matter has taken refuge in the spongy tissue\nitself, in the _spongioplasm_.\n\nAccording to other histologists, the comparison of protoplasm to a\nspongy mass does not give the most exact idea, and, in particular, it\ndoes not furnish the most general idea. It would be far better to say\nthat the protoplasm possesses the structure of foam or lather. As was\nseen by Kunstler in 1880, a comparison with some familiar objects gives\nthe best idea. Nothing could be more like protoplasm physically than\nthe culinary preparation known as _sauce mayonnaise_, made with the aid\nof oil and a liquid with which oil does not mix. Emulsions of this kind\nwere made artificially by B\u00fctschli. He noted that these preparations\nmimicked all the aspects of cellular protoplasm. Thus, in the living\ncell there is a mixture of two liquids, non-miscible and of unequal\nfluidity. This mixture gives rise to the formation of little cells. The\nmore consistent substance forms their supporting framework (Leydig\u2019s\nspongioplasm), while the other, which is more fluid, fills its interior\n(hyaloplasm).\n\nHowever that may be, whether the primitive organization of the cellular\nprotoplasm be that of a sponge, as is asserted by Leydig, or that of\na _sauce mayonnaise_, as is claimed by B\u00fctschli and Kunstler, the\ncomplexity does not rest there. Further recourse must be made to\nanalysis. Just as the tissue of a sponge, when torn, shows the fibres\nwhich constitute it, so the spongioplasm, the parietal substance,\nis exhibited as formed of a tangle of fibrils, or better still, of\nfilaments or ribbons (in Greek, _mitome_), which are called _chromatic\nfilaments_, because they are deeply stained when the cell is plunged\ninto aniline dye. In each of these filaments, the substance of which\nis called chromatin, the devices of microscopic examination enable\nus to discover a series of granulations like beads on a string, the\n_microsomes_ or bioblasts, connected one with the other by a sort of\ncement, Schwartz\u2019s _linin_, which is a kind of nuclein.\n\nAnd let us add, to complete this summary of the constitution of\ncellular protoplasm, that it presents, at any rate at a certain moment,\na remarkable organ, the _centrosome_, which plays an important part\nin cellular division. Its pre-existence is not certain. Some writers\nmake it issue from the nucleus. At the moment of cellular division it\nappears like a compressed mass of granulations, which may be deeply\nstained. Around it is seen a clear unstainable zone, called the\nattraction-sphere; and finally, beyond this is a crown of stri\u00e6, which\ndiverge like the rays of a halo\u2014_i.e._, the _aster_. In conclusion,\nthere are yet in the cellular body three kinds of non-essential bodies:\nthe vacuoles, the leucites, and various inclusions. The _vacuoles_ are\ncavities, some inert, some contractile; the _leucites_ are organs for\nthe manufacture of particular substances; the _inclusions_ are the\nmanufactured products, or wastes.\n\n_The Nucleus_.\u2014Every cell capable of living, growing, and multiplying,\npossesses a _nucleus_ of constitution very analogous to the cellular\nmass which surrounds it. The anatomical elements in which no nucleus\nis found, such as the red globules of blood in adult mammals, are\nbodies which are certain, sooner or later, to disappear. There is\ntherefore no real cell without a nucleus, any more than there is a\nnucleus without a cell. The exceptions to this law are only apparent.\nHistologists have examined them one by one, and have shown their purely\nspecious character. We may therefore lay aside, subject to possible\nappeal from this decision, organisms such as Haeckel\u2019s _monera_ and\nthe problem of finding out if bacteria really have a nucleus. The very\ngreat, if not the absolute generality of the nuclear body, must be\nadmitted.\n\nIt hence follows that there is a nuclear protoplasm and a nuclear\njuice, just as we have seen that there is a protoplasm and a cellular\njuice. What was just said of the one may now be repeated of the other,\nand perhaps with even more emphasis. The nuclear protoplasm is a\nfilamentary mass sometimes formed of a single mitome or cord, folded\nover on itself and capable of being unrolled. The mitome in its turn\nis a string of microsomes united by the cement of the linin. These are\nthe same constituent elements as before, and the language of science\ndistinguishes them one from the other by a prefix to their name of\nthe words _cyto_ or _karyo_, which in Greek signify cell and nucleus,\naccording as they belong to one or the other of these organs. These\nare mere matters of nomenclature, but we know that in the descriptive\nsciences such matters are not of minor importance.\n\nWe have just indicated that in a state of repose,\u2014that is to say, under\nordinary conditions,\u2014the structure of a nucleus reproduces clearly the\nstructure of the cellular protoplasm which surrounds it. The nuclear\nessence is best separated from the spongioplasm. It takes more clearly\nthe form of a filamentary thread, and the filaments themselves\n(mitome) show very thick chromatic granulations, or microsomes,\nconnected by the linin.\n\nAt the moment of reproduction of the cell these granulations blend\ninto a stainable sheath which surrounds the filaments, and the latter\ndispose themselves so as to form a single thread. This chromatic\nfilament, which has now become a single thread, is shortened as\nit thickens (_spireme_); it is then cut into segments, twelve or\ntwenty-four in the case of animals and a larger number in the case of\nplants. These are _chromosomes_, or _nuclear segments_, or _chromatic_\nloops. Their part is a very important one. They are constant in number\nand permanent during the whole of the life of the cell. Let us add that\nthe nucleus still contains accessory elements (nucleoli).\n\n_The R\u00f4le of the Nucleus_.\u2014Experiment has shown that the nucleus\npresides over the nutrition, the growth, and the conservation of\nthe cell. If, following the example of Balbiani, Gruber, Nussbaum,\nand W. Roux of Leipzig, we cut into two a cell without injuring the\nnucleus, the fragment which is denuded of the nucleus continues to\nperform its functions for some time in the ordinary manner, and in\nsome measure in virtue of its former impulse. It then declines and\ndies. On the contrary, the fragment provided with the nucleus repairs\nits wound, is reconstituted and continues to live. Thus the nucleus\ntakes a very remarkable part in the reproduction of the cell, but it\nis still a matter of uncertainty whether its r\u00f4le is here subordinated\nto that of the cellular body, or if it is pre-eminent. However that\nmay be, it follows from this experiment that the nucleus presents all\nthe characteristics of a vigorous vitality, and that it is in its\nprotoplasm that the chemists should be able to find the compounds, the\nspecial albuminoids, which, _par excellence_, form living matter.\n\n\n \u00a7 3. THE PHYSICAL CONSTITUTION OF LIVING MATTER. THE MICELLAR THEORY.\n\n\n_Physical Constitution of Living Matter_.\u2014Microscopic examination\ndoes not take us much farther. The microscope, with the strongest\nmagnification of which it is capable at present, shows us nothing\nbeyond these links of aligned microsomes forming the species of\nprotoplasmic thread or mitome, whose cellular body is a confused\ntangle or a very tangled ball. It is not probable that direct sight\ncan penetrate much farther than this. No doubt the microscope, which\nhas been so vastly improved, is capable of still further improvement.\nBut these improvements are not indefinite. We have already reached a\nlinear magnification of 2000, and theory tells us that a magnification\nof 4000 is the limit which cannot be passed. The penetrating power of\nthe instrument is therefore near its culminating point. It has already\ngiven almost all that we have a right to expect from it.\n\nWe must, however, penetrate beyond this microscopic structure at which\nthe sense of sight has been arrested. How is this to be done? When\nobservation is arrested, hypothesis takes its place. Here there are two\nkinds of hypotheses, the one purely anatomical, the other physical.\nAnatomically, beyond the visible microsomes there have been imagined\ninvisible hyper-microscopic corpuscles, the plastidules of Haeckel,\nthe idioblasts of Hertwig, the pangenes of de Vries, the plasomes of\nWiesner, the gemmules of Darwin, and the biophores of Weismann.\n\nBiologists who have not got all that they hoped from microscopic\nstructure are therefore thrown back on hyper-microscopic structure.\n\nIt is very remarkable that all this profound knowledge of structure has\nbeen so sterile from the point of view of the knowledge of cellular\nfunctional activity. All that is known of the life of the cell has\nbeen revealed by experiment. Nothing has resulted from microscopic\nobservation but ideas as to configuration. When it is a question of\ngiving or imagining an explanation of vital facts, of heredity, etc.,\nbiologists unable to supply anything beyond the details of structure\nrevealed by anatomy have had recourse to hypothetical elements,\ngemmules, pangenes, biophores, and different kinds of determinants.\n\nAnatomy never has explained and never will explain anything. \u201cHappy\nphysicists!\u201d wrote Loeb, \u201cin never having known the method of research\nby sections and stainings! What would have happened if by chance a\nsteam engine had fallen into the hands of a histological physicist?\nHow many thousands of sections differently stained and unstained, how\nmany drawings, how many figures, would have been produced before they\nknew for certain that the machine is an engine, and that it is used for\ntransforming heat into motion!\u201d\n\nThe study of physical properties, continued on rational hypotheses, has\nalso thrown some light on the possible constitution of living matter.\nThe gap between microscopical structure and molecular or chemical\nstructure has thus been filled.\n\nThe consideration of the properties of _turgescence_ and of _swelling_,\nwhich very generally belong to organized tissues, and therefore to the\norganic substance of protoplasm, has enabled us to obtain some idea of\nits ultra-microscopic constitution. If we wet a piece of sugar or a\nmorsel of salt, before they are dissolved they absorb and imbibe the\nwater without sensibly increasing their volume. It is quite otherwise\nwith a tissue (_i.e._, with a protoplasm) when weakened in water as a\npreliminary. The tissue, plunged into the liquid, absorbs it, swells,\nand often grows considerably. And this water does not lodge in the\ngaps, in pre-existing lacunar spaces, for organic matter presents no\ngaps of this kind. It does not resemble a porous mass with capillary\ncanals, such as sandstone, tempered mortar, clay, or refined sugar.\nThe molecules of water interpose between and separate the organic\nmolecules, thus increasing by a sort of intussusception the intervals\nseparating the one from the other\u2014molecular intervals escaping the\nsenses, as do the molecules themselves because they are of the same\norder of magnitude.\n\n_Micellar Theory._\u2014While pondering over this phenomenon, an eminent\nphysiologist, N\u00e4geli, was led in 1877 to propose his _micellar theory_.\nMicell\u00e6 are groups of molecules in the sense in which physicists\nand chemists use the word. They are molecular structures with a\nconfiguration. They rapidly absorb water and are capable of fixing a\nmore or less thick and adherent layer of it to their surface. In a\nword, they are aggregates of organic matter and water.\n\nThere is therefore every reason for believing that the _microsomes_ of\nspongy protoplasm, the physical support or basis of cellular life,\nare _groups of micell\u00e6_ formed of albuminoid substances and water.\nThese clustered forms, these micell\u00e6, are not absolutely peculiar to\norganized matter. Pfeffer, the learned botanist, has pointed them\nout under another name, _tagmata_, in the membranes of chemical\nprecipitates.\n\nBeyond this limit analysis finds nothing but the chemical molecule\nand the atom. So that if we wish to reconstruct the hierarchy of the\nmaterials of constitution of the protoplasm in order of ascending\ncomplexity, we shall find at the foundation the atom or atoms of simple\nbodies. They are principally carbon, hydrogen, oxygen, nitrogen, the\nelements of all organic compounds, to which may be added sulphur\nand phosphorus. At the head we have the albuminoid molecule, or the\nalbuminoid molecules, aggregates of the preceding atoms. In the third\nstage the micell\u00e6 or tagmata, aggregates of albuminoids and water, are\nstill too small to be observed by the senses. They unite in their turn\nto form the microsomes, the first elements visible to the microscope.\nThe microsomes, cemented by linin, form the filaments or links which\nare called mitomes. The living protoplasm is therefore nothing but a\nchain, or tangled skein, or a spongy skeleton formed by its filaments.\n\nSuch is the typical constitution of living matter according to\nmicroscopic observation, supplemented by a perfectly reasonable\nhypothesis, which is, so to speak, only a translation of one of its\nmost evident physical properties. This relatively simple scheme has\nbecome a complex scheme in the hands of later biologists. On the\nmicellar hypothesis, which seems almost inevitable in its character,\nnew hypotheses have been grafted, merely for the sake of convenience.\nHence, we are led farther and farther from the real truth, and this is\nwhy, in order to explain the phenomena of heredity, we find ourselves\ncompelled to intercalate hypothetical elements between micell\u00e6 and the\nmicrosome in the higher hierarchy quoted above\u2014gemmules, pangenes,\nplasomes, which are only mental pictures or simple images to represent\nthem.\n\n\n\u00a7 4. THE INDIVIDUALITY OF COMPLEX BEINGS. LAW OF THE CONSTITUTION OF\nORGANISMS.\n\n\n_Individuality of Complex Beings._\u2014From the cellular doctrine follows a\nremarkably suggestive conception of living beings. The metazoa and the\nmetaphytes\u2014that is to say, the multicellular living beings which may be\nseen with the eyes and do not require the microscope to reveal them\u2014are\nan assemblage of anatomical elements and the posterity of a cell.\nThe animal or the plant, instead of being an individual unity, is a\n\u201cmultitude,\u201d a term which is used by Go\u00ebthe himself when pondering, in\n1807, over the doctrine taught by Bichat; or, according to the equally\ncorrect expression of Hegel, it is a \u201cnation\u201d; it springs from a common\ncellular ancestor, just as the Jewish people sprang from the loins of\nAbraham.\n\nWe now picture to ourselves the complex living being, animal or plant,\nwith its configuration which distinguishes it from every other being,\njust as a populous city is distinguished by a thousand characteristics\nfrom its neighbour. The elements of this city are independent and\nautonomous for the same reason as the anatomical elements of the\norganism. Both have in themselves the means of life, which they neither\nborrow nor take from their neighbours nor from the whole. All these\ninhabitants live in the same way, are nourished and breathe in the\nsame manner, all possessing the same general faculties, those of man;\nbut each has besides, his profession, his trade, his aptitudes, his\ntalents, by which he contributes to social life, and by which in his\nturn he depends on it. Professional men, the mason, the baker, the\nbutcher, the manufacturer, the artist, carry out different tasks and\nfurnish different products, the more varied, the more numerous and the\nmore differentiated, in proportion as the social state has reached a\nhigher degree of perfection. The living being, animal or plant, is a\ncity of this kind.\n\n_Law of the Constitution of Organisms._\u2014Such is the complex animal.\nIt is organized like the city. But the higher law of this city is\nthat the conditions of the elementary or individual life of all the\nanatomical citizens are respected, the conditions being the same for\nall. Food, air, and light must be brought everywhere to each sedentary\nelement; the waste must be carried off in discharges which will free\nthe whole from the inconvenience or the danger of such debris; and that\nis why we have the different forms of apparatus in the circulatory,\nrespiratory, and excretory economy. The organization of the whole\nis therefore dominated by the necessities of cellular life. This is\nexpressed in _the law of the constitution of organisms_ formulated by\nClaude Bernard. The organic edifice is made up of apparatus and organs,\nwhich furnish to each anatomical element the necessary conditions and\nmaterials for the maintenance of life and the exercise of its activity.\nWe now understand what is the life, and at the same time what is the\ndeath, of a complex being. The life of the complex animal, of the\nmetazoon, is of two degrees; at the foundation, the activity proper\nto each cell, _elementary life_, cellular life; above, the forms of\nactivity resulting from the association of the cells, _the life of the\nwhole_, the sum or rather the complex of elementary partial lives.\nThere is a solidarity between them produced by the nervous system,\nby the community of the general circulatory, respiratory apparatus,\netc., and by the free communication and mixture of the liquids which\nconstitute the media of culture for each cell. We shall have an\nopportunity of recurring to current ideas as to the morphological\nconstitution of organisms.\n\n\n\n\n CHAPTER III.\n\n THE CHEMICAL UNITY OF LIVING BEINGS.\n\n The varieties and essential unity of the protoplasm\u2014Its affinity for\n oxygen\u2014The chemical composition of protoplasm\u2014Its characteristic\n substances.\u2014\u00a7 1. The different categories of albuminoid\n substances\u2014Nucleo-proteids\u2014Albumins and histones\u2014Nucleins.\u2014\u00a7\n 2. Constitution of nucleins.\u2014\u00a7 3. Constitution of histones and\n albumins\u2014Schultzenberger\u2019s analysis of albumin\u2014Kossol\u2019s analysis\u2014The\n hexonic nucleus.\n\n\nThe chemical unity of living beings corresponds to their morphological\nunity.\n\n_The Varieties and Essential Unity of the Protoplasm._\u2014One essential\nfeature of the living being is that it is composed of matter peculiar\nto it, which is called _living matter_, or _protoplasm_. But this is\na somewhat incorrect way of expressing the facts. There is no unique\nliving matter, no single protoplasm; their number is infinite, there\nare as many as there are distinct individuals. However like one man may\nbe to another, we are compelled to admit that they differ according to\nthe substance of which they are constituted. That of the first offers\na certain characteristic personal to the first, and found in all his\nanatomical elements; similarly for the second. With Le Dantec we shall\nsay that the chemical substance of Primus is not only of the substance\nof man, but in all parts of his body and in all his constituent cells\nit is the exclusive substance of Primus; and, in the same way, the\nliving matter of another individual Secundus will carry everywhere his\npersonal impress, which differs from that of Primus.\n\nBut it is none the less true that this absolute specificity is based\nwith certainty only on differences which from the chemical point\nof view are exceedingly slight. All these protoplasms have a very\nanalogous composition. And, if we regard as negligible the smallest\nindividual, specific, generic, or ordinal variations we may then speak\nin a general manner of _protoplasm_ or _living matter_.\n\nExperiment shows us, in fact, that the real living substance\u2014apart\nfrom the products it manufactures and can retain or reject\u2014is in every\ncell tolerably similar to itself. The fundamental chemical resemblance\nof all protoplasms is certain, and thus we may speak of their typical\ncomposition. We may sum up the work of physiological chemistry for the\nlast three quarters of a century by affirming that it has established\nthe chemical unity of all living beings\u2014that is to say, a very notable\nanalogy in the composition of their protoplasm.\n\nThis living matter is essentially a mixture of the proteid or\nalbuminoid substances, to which may be added other categories of\nimmediate principles, such as carbohydrates and fatty matters. But\nthe latter are of secondary importance. The essential element is the\nproteid substance. The most skilful chemists have tried for more than\nhalf a century to discover its composition. Only during the last few\nyears\u2014thanks to the researches of Kossel, the German chemist, following\non those of Schultzenberger and Miescher\u2014we are beginning to know the\nouter walls or the framework of the albuminoid molecule; in other\nwords, its chemical nucleus.\n\n_Physical Characters of Protoplasm._\u2014About 1860 Ch. Robin thought\nthat he had defined living matter sufficiently\u2014or, at least, as\nperfectly as could be expected at that time\u2014by attributing to it\nthree physical characteristics. They were:\u2014Absence of homogeneity,\nmolecular symmetry, and the association of three orders of immediate\nprinciples\u2014albuminoids, carbohydrates and fats. These characteristics\nassist, but do not suffice, to define the organization.\n\nNo doubt the characteristics must be completed by the addition of a\ncertain number of more subtle physical features.\n\nOne of them refers to the structure of protoplasm as revealed by the\nmicroscope. Throughout the whole of the living kingdom, from the\nbacteria studied by Kunstler and Busquet to the most complicated\nprotozoa, protoplasmic matter presents the same constitution, and in\nconsequence, this structure of the protoplasm must be considered as\none of its distinctive characters. It is not homogeneous; it is not\nthe last term of the visible organization: it is itself organized.\nExperiment shows that it does not resist breaking up or crushing.\nMutilations cause it to lose its properties. As for the kind of\nstructure that it presents, it may be expressed by saying that it is\nthat of a foamy emulsion.\n\nWe saw above that our knowledge as to the physical condition of\nprotoplasm has been completed by the theories of B\u00fctschli\u2019s micell\u00e6 or\nPfeffer\u2019s tagmata.\n\n_Properties of the Protoplasm. Its Affinity for Oxygen._\u2014From the\nchemical point of view, living matter presents a very remarkable\nproperty\u2014namely, a great affinity for oxygen. It absorbs it\nso greedily that the gas cannot remain in a free state in its\nneighbourhood. Living protoplasm, therefore, exercises a reducing\npower. But it does not absorb oxygen in this way for its own advantage;\noxygen is not absorbed, as was supposed thirty years ago, to supply\nfuel wherewith to burn the protoplasm. The products are not those of\nits oxidation, of its own disintegration. They are the products of\ncombustion of the reserve-stuff which is incorporated in it. These\nsubstances have been supplied to it from without, like the oxygen\nitself, with the blood. This was proved by G. Pfl\u00fcger in 1872 to\n1876. The protoplasm is only the focus, the scene, or the factor of\ncombustion. It is not its victim, it does not itself furnish the fuel.\nIt works like the chemist, who obtains a reaction with the substances\nthat are given to him.\n\nAs for the reducing power of protoplasm, A. Gautier in 1881 and Ehrlich\nin 1890 have given fresh proofs. A. Gautier in particular has insisted\nthat the phenomena of combustion take place, so to speak, outside the\ncell, and at the expense of the products which surround it; while on\nthe contrary the really active and living parts of the nucleus and of\nthe cellular body, work protected by the oxygen, as in the case of\nanaerobic microbes.\n\nThis result is of great importance. Burdon Sanderson, the late\nlearned professor of physiology at the University of Oxford, has not\nhesitated to compare it to the discovery of respiratory combustion\nby Lavoisier. There is no doubt some exaggeration in the comparison;\nbut there is, on the other hand, no less exaggeration in supposing\nthat it is not of great importance. We may no longer in these days\nspeak without reservation of the vital vortex of Cuvier, and of the\nincessant twofold movement of assimilation and dissimilation which is\never destroying living matter and building it up again. In reality, the\nliving protoplasm varies very little; it only undergoes oscillations of\nvery slight extent; it is the materials, the reserve stuff on which it\noperates, which are subject to continual transformations.\n\n_Chemical Composition of Protoplasm._\u2014One of the the three\ncharacters attributed by Ch. Robin to living matter was its chemical\ncomposition, of which little was known in his time. He insisted on\nthe constant presence in the living elements of three orders of\nimmediate principles\u2014proteid substances, carbohydrates, and fatty\nbodies. In reality the proteid substances, or albuminoids, alone are\ncharacteristic. The two other groups, carbohydrates and fatty bodies,\nare rather the signs and the products of the vital activity, than\nconstituents of the matter on which it is exercised.\n\nIt is therefore on the knowledge of the proteid substances that all the\nsagacity of biological chemists has been exercised. Their efforts for\nthirty years, and particularly in the last few years, have not been\nbarren; they enable us to give a first rough sketch of the constitution\nof these substances.\n\n\n \u00a7 1. THE CHARACTERISTIC SUBSTANCES OF THE PROTOPLASM. THE\n NUCLEO-PROTEIDS.\n\n\n_The Different Categories of Albuminoid Substances._\u2014Albuminoid or\nproteid substances are extremely complex compounds, much more so than\nany of those which are being constantly studied by the chemist.\nThey also are to be found in great variety. It has been difficult to\nseparate them one from the other, to characterize them rigorously,\nor, in other words, to classify them. However, it has been done now,\nand we distinguish three classes which are differentiated at once\nfrom the physiological and from the chemical points of view. The\nfirst comprises the complete or typical albuminoids. They are the\n_proteids_ or _nucleo-albuminoids_. They are to be found in the most\nactive and most living parts of the protoplasm, and therefore in the\nspongioplasm of the cell and around the nucleus. The second group\nis formed of _albumins_ and _globulins_, compounds already simpler,\nfragments derived from the destruction of the preceding, into which\nthey enter as constituent elements. In the isolated state they do not\nbelong to the really living protoplasm; they exist in the cellular\njuice, in the interstitial and circulating liquids in the blood\nand in the lymph. The third category comprises real but incomplete\nalbuminoids. They are to be found in the portions of the economy which\nhave a specialized or attenuated life, and are destined to serve as\na support to the more active elements\u2014_i.e._, they contribute to the\nbuilding up of the bony, cartilaginous, conjunctive, elastic tissues.\nThey are called _albumoids_. It is naturally the first group, that of\nthe proteids\u2014_i.e._, of the complete and characteristic compounds of\nthe living substance\u2014upon which the attention of the physiologists\nmust be fixed. It is only quite recently that the clear definition of\nthese substances has been given, and proteid compounds detected in the\nconfused mass.\n\n_The Nucleo-proteids._\u2014This progress in the characterization and\nspecification of the proteids required in the first place a knowledge\nof two particular compounds, the _nucleins_ and the _histones_. This\ndid not become possible until after the researches of Miescher and\nKossel on the nucleins, which went on from 1874 to 1892, and those of\nLilienfeld and d\u2019Yvor Bang on the histones, from 1893 to 1899. The\ncomplete albuminoids are constituted by the combination of two kinds of\nsubstances\u2014albumins or histones on the one hand, and nucleins on the\nother. By combining solutions of albumins or histones with solutions\nof nuclein, the synthesis of the proteid is effected. The study of\nthe properties and characteristics of these nucleo-albumins and\nnucleo-histones is going on at the present moment. It is being carried\nout with much method and with wonderful patience by the German school.\n\nAll the proteids contain phosphorus in addition to the five chemical\nelements, carbon, oxygen, hydrogen, nitrogen, and sulphur, which are\ncommon to the other albuminoids. Another interesting feature in their\nhistory is that the action of the gastric juice divides them into\ntheir two constituents:\u2014the nuclein, which is deposited and resists\nthe destructive action of the digestive liquid, and the albumin or\nhistone, which on the contrary experiences this action with the usual\nconsequences. Thus the gastric juice furnishes a process which is very\nsimple and very convenient in the analysis of the proteids.\n\n_Localization of the Nucleo-Proteids._\u2014What we said before as to\nthe important physiological r\u00f4le of the cellular nucleus may arouse\nthe expectation that in it will be found the living matter which\nis chemically the most differentiated, the albuminoids of highest\nrank\u2014_i.e._, the nucleo-proteids and their constituents. Not that they\nwould not be found in the protoplasm of the rest of the cell, but there\nis certainly a risk that they would be less concentrated there and more\nblended with accessory products; they are there connected with much\nmore secondary vital functions. This conclusion inspired the early\nresearches of Professor Miescher, of Basle, in 1874, and, twenty years\nlater, those of Professor Kossel, one of the most eminent physiological\nchemists in Germany.\n\nIn fact, these compounds have been found in all tissues which are rich\nin cellular elements with well-developed nuclei. The white globules\nof the blood furnished to Lilienfeld the first nucleo-histone ever\nisolated. The red globules themselves, when they possess a nucleus,\nwhich is the case in birds and reptiles as well as in the embryo of\nmammals, contain a nucleo-proteid which was easily isolated by Plosz\nand Kossel. Hammarsten, the Swedish chemist, who has acquired a\ngreat reputation from his researches in other domains of biological\nchemistry, prepared the nucleo-proteids of the pancreas in 1893. They\nhave been obtained from the liver, from the thyroid gland (Ostwald),\nfrom brewers\u2019 yeast (Kossel), from mushrooms, and from barley (Petit).\nThey have been detected in starchy bodies and in bacteria (Galeotti).\n\n\n \u00a7 2. CONSTITUTION OF NUCLEINS.\n\n\n_Constitution of Nucleins._\u2014Our path is already marked out if we wish\nto penetrate farther into the constitution of these proteids, which are\nthe immediate principles highest in complexity among those which form\nthe living protoplasm. We must analyze the two components, the albumins\nand the histones on the one hand, and the nucleins on the other. As for\nthe nucleins, this has already been done, or very nearly so.\n\nKossel, in fact, decomposed the nuclein by a series of very carefully\narranged operations, and has reduced it step by step to its\ncrystallizable organic radicals. At each stage that we descend in the\nscale of simplification a body appears which is more acid and more rich\nin phosphorus. At the third stage we come to phosphoric acid itself.\nThe first operation divides the nuclein into two substances: the new\nalbumin and nucleinic acid. After separating these elements they can\nbe reunited: a solution of albumin with a solution of nucleinic acid\nreconstitutes the nuclein. A second operation separates the nucleinic\nacid in its turn into three parts. One is a body of the nature of\nthe sugars\u2014_i.e._, a carbohydrate. The appearance of a sugar in this\nportion of the molecule of nucleinic acid is an interesting fact and\nfertile in results. The second part is constituted by a mixture of\nnitrogenous bodies, well known in organic chemistry under the name of\n_xanthic bases_ (xanthin, hypoxanthin, guanin, and adenin). The third\npart is a very acid body and full of phosphorus\u2014thymic acid. If in a\nthird and last operation the thymic acid is analyzed, it is finally\nseparated into phosphoric acid and into thymene, a crystallizable base,\nand thus we are brought back to the physical world, for all these\nbodies incontestably belong to it.\n\n\n \u00a7 3. THE CONSTITUTION OF HISTONES AND ALBUMINS.\n\n\n_Constitution of Histones._\u2014But we are only half-way through our task.\nWe are acquainted in its origin with one of the genealogical branches\nof the proteid, the nucleinic branch. We must also learn something\nof the other branch, the albumin or histone branch. But on this side\nthe problem assumes a character of difficulty and complexity which is\nadmirably adapted to discourage the most untiring patience.\n\nThe analysis of albumin for a long time baulked the chemist \u201cHere,\u201d\nsaid Danilewsky, \u201cwe come to a closed door which resists all our\nefforts.\u201d We know how vastly interesting what is taking place on the\nother side must be, but we cannot get there. We get a mere glimpse\nthrough the cracks or chinks which we have been able to make.\n\nThis analysis of albuminous matter at first requires great precautions.\nThe chemist finds himself in the presence of architecture of a very\nsubtle kind. The molecule of albumin is a complex edifice which has\nused up several thousand atoms. To perceive the plan and structure, it\nmust be dismantled and separated into parts which are neither too large\nnor too small. Such careful demolition is difficult. Processes too\nrough or too violent will reduce the whole to the tiniest of fragments.\nIt is a statue which may be reduced to dust, instead of being separated\ninto recognizable fragments, easily fitted in place along their\nfractured faces.\n\n_Analysis of Albumin by Sch\u00fctzenberger._\u2014Sch\u00fctzenberger, a chemist\nof great merit, attempted (about 1875) this thankless task. Others\nbefore him had experimented in various ways. Two Austrian scientists,\nHlasitwetz and Habermann, in 1873, and a little later Drechsel in 1892,\nhad used concentrated hydrochloric acid to break down albumin. They\nalso employed bromine for the same purpose. More recently Fuerth had\nused nitric acid with a similar object. Sch\u00fctzenberger tried another\nway. The battering ram which he used against the edifice of albumin\nwas a concentrated alkali, baryta. He warmed the white of an egg with\nbarium hydrate in a closed vessel at a temperature of 200\u00b0. The albumin\nof egg then divides into a certain number of simpler groups. The\ndifficulty is to isolate and to recognize each part in this mass of the\nmaterials of demolition. That can be done by the aid of the processes\nof direct analysis. By mentally combining these different fragments,\nthe original building is reconstructed. This method of demolition is\ncertainly too rough and violent. Sch\u00fctzenberger\u2019s operation gives us\nvery fine fragments\u2014small molecules of free hydrogen, of ammonia, of\ncarbonic, acetic, and oxalic, acids which reveal extreme pulverization.\nThese products represent about a quarter of the total mass. The other\nthree-quarters are formed of larger fragments, the examination of which\nis most instructive. They belong to four groups. The first comprises\nfive or six bodies, amido-acids or _leucins_. It proves the existence\nin the molecule of albumin of compounds of the series of fats\u2014_i.e._,\narranged in an open chain. The second group is formed by tyrosin and\nkindred products\u2014_i.e._, by the bodies of the aromatic series, which\nforce us to acknowledge the presence in the molecule of albumin of a\nbenzene nucleus. The third group forms around the nucleus known to\nchemists under the name of pyrrol. The fourth comprises bodies such as\nthe glucoproteins, connected with the sugars, or carbohydrates.\n\nDoes the fact that the molecule of albumin is destroyed in producing\nthese compounds raise the question as to whether it implies the idea\nthat in reality they pre-exist in it? Chemists are rather inclined to\nadmit this. However, the conclusion does not appear to be permissible.\nDuclaux considers it doubtful. It is not certain that all these\nfragmentary bodies pre-exist in reality, and it is no more certain that\na simple bringing of them together represents the primitive edifice.\nMaterials of demolition from a house that has been pulled down give no\nidea of its natural architectural character. There is only one way of\njustifying the hypothesis, and that is to reconstitute the original\nmolecule of albumin by bringing the fragments together. We have not got\nto that stage yet. The era of syntheses of such complexity is more or\nless near, but it has certainly not yet begun.\n\nMoreover, it is not correct to say that the simple juxtaposition of the\nsurfaces of fracture will reproduce the initial body. The fragments, so\nfar as analysis has obtained them, are not absolutely what they might\nhave been in the original structure. There they adhered the one to the\nother, not only by the mere contact of their surfaces of fracture, as\nis supposed, but in a slightly more complex manner. The fragments of\nthe molecule are joined by bonds. We can picture them to ourselves\nby supposing these bonds to be like hooks. The hooks, which could\nonly be broken by violence, are called by the chemists _satisfied\natomicities_. These atomicities, set free by the breaking up, cannot\nremain in this condition; they must be satisfied anew. The hook tries\nto attach itself. In Sch\u00fctzenberger\u2019s experiment the addition of water\nprovides for this necessity. A molecule of water (H\u2304{2}O) splits\ninto two, the hydrogen (H) on the one side and the hydroxyl (OH) on\nthe other. These two elements cling to the liberated bonds of the\nfragments of the molecule of albumin, and thus the bodies were found\ncomplete. Sch\u00fctzenberger\u2019s experiment was too violent, too radical,\nand it gave too large a number of fragments, with their free hooks and\natomicities unsatisfied, for rather a large proportion of the water\nadded disappeared during the experiment. In one case this quantity was\nas much as 17 grammes per 100 grammes of albumin. The molecules of this\nwater were employed in the reparation of the incomplete fragmentary\nmolecules of the albumin.\n\nIt follows that Sch\u00fctzenberger\u2019s experiment gave too large a number of\nvery small pieces corresponding to far too great a pulverization. The\nvery small fragments are the molecules of acids such as acetic acid,\noxalic acid, carbonic acid, molecules of ammonia, and even of hydrogen,\nwhich we know we are setting free.\n\nBut, apart from these products which represent a quarter of the\nmolecule of albumin submitted to analysis, the other three quarters\nrepresent larger fragments which may be considered as the real\nconstituents of the building. Thus we find four kinds of groups which\nmay be accepted as natural. The first of these groups is that of the\nleucins or amido-acids. It proves the existence in the molecule of\nalbumin of compounds of the fatty series. There is also an aromatic\ngroup\u2014a pyridine group\u2014and a group belonging to the category of sugars.\nImagine a certain grouping of these four series. This would be the\nnucleus of the molecule of albumin. If we graft on to this nucleus, on\nto this framework as it were, so many annexes, or lateral chains, the\nbuilding will be loaded with embellishments; it will have been made\nunstable and _ipso facto_ appropriate for the part that it plays in the\nincessant transformations of the organism.\n\n_Kossel\u2019s Analysis. Hexonic Nucleus._\u2014Kossel has approached the\nproblem in another fashion. He did not attempt to attack the albumin\nof the egg. This body is, in fact, a heterogeneous mixture as complex\nas the needs of the embryo of which it forms the food. Kossel tried\na physiologically simpler albuminoid. He got it from an anatomical\nelement having no nutritive r\u00f4le, of a very elementary organization\nand physiological functional activity, and yet one of energetic\nvitality\u2014the male generating cell. Instead of the hen\u2019s egg he\ntherefore analyzed the milt of fish, and, in the first place, of\nsalmon. As was to be expected from what has been said of the proteids,\nthis living matter gives a combination of the nuclein, already known,\nwith an albumin. The latter is abundant, forming a quarter of the\ntotal mass. Its reaction is strongly alkaline, which is the general\ncharacteristic of the variety of albumin known by the name of histones.\nMiescher, the learned chemist of Basle, who had noticed this basic\nalbumin when working on the Rhine salmon, gave it the name of protamin.\nThis is the substance submitted by Kossel to analysis in preference\nto the albumin of egg, so dear to the chemists who had preceded him.\nThe disintegration of this molecule, instead of giving the series of\nbodies obtained by Sch\u00fctzenberger, gave but one, a real chemical base,\n_arginin_. At the first trial the albumin examined was reduced to a\nsimple crystallizable element. The conclusion was obvious. The protamin\nof salmon is the simplest of albumins. To form this elementary proteid\nsubstance a hexonic base with water is all that is required.\n\nContinuing on these lines other male generating cells were examined\nand a series of protamines constructed on the same type was found,\nand these albuminous bodies proved to be formed of a base or mixture\nof analogous hexonic bases: arginin, histidin, and lysin\u2014all bodies\nclosely akin in their properties and entirely belonging to the physical\nworld.\n\nOnce aware of the existence of this fundamental nucleus, chemists\nfound it in the more complex albumins where it had been missed. It was\nfound in the albumin of egg hidden under the mass of other groups.\nIt was recognized in all animal or vegetable albumins. The nuclei\nof Sch\u00fctzenberger may be missing. Hexonic bases are the constant\nand universal element of all varieties of albumins. They prevail in\nthe chemical nucleus of the albuminous molecule, and perhaps as is\nsuggested by Kossel, they may form it exclusively. All the other\nelements are superadded and accessory. The essential type of this\nmolecular edifice, sought for so long, is known at last.\n\n_Conclusion._\u2014To sum up, the chemical unity of living beings is\nexpressed by saying that living matter, protoplasm, is a mixture or a\ncomplex of proteid substances with an hexonic nucleus.\n\n\n\n\n CHAPTER IV.\n\n THE TWOFOLD CONDITIONING OF VITAL PHENOMENA. IRRITABILITY.\n\n Appearance of internal activity of the living being\u2014Vital phenomena\n regarded as a reaction of the ambient world.\u2014\u00a7 1. Extrinsic\n conditions\u2014The optimum law.\u2014\u00a7 2. Intrinsic conditions\u2014The structure\n of organs and apparatus\u2014How experiment attacks the phenomena of life.\n Generalization of the law of inertia\u2014Irritability.\n\n\n_Instability. Mutability. The Appearance of Internal Activity of the\nLiving Being._\u2014One of the most remarkable characteristics of the living\nbeing is its instability. It is in a state of continual change. The\nsimplest of the elementary beings, the plastid, grows and goes on\ngrowing and becoming more complex, until it reaches a stage at which it\ndivides, and thus rejuvenated it commences the upward march which leads\nit once again to the same segmentation. Its evolution is thus betrayed\nby its growth, by the variations of form which correspond to it, and by\nits division.\n\nIf it be a question of beings higher in organization than the cellular\nelement the evolutionary character of this mutability becomes more\nobvious. The being is formed, it grows; then in most cases, after\nhaving passed through the stages of youth and adult age, it grows old,\ndeclines and dies, and is disorganized after having gone through\nwhat we may call an ideal trajectory. This march in a fixed direction\nwith its points of departure, its degrees, and its termination, is a\nrepetition of the path that the ancestors of the living being have\nalready followed.\n\nHere, then, is a characteristic fact of vitality, or rather there\nare two facts. The one consists in this morphological and organic\nevolution, the negation of immutability, the negation of the indefinite\nmaintenance of a permanent state or form which is regarded, on the\ncontrary, as the condition of inert, fixed stable bodies, eternally at\nrest. The other consists in the repetition, realized by this evolution,\nof the similar evolution of its ancestors; this is a fact of heredity.\nFinally, evolution is always in a cycle\u2014that is to say, that it comes\nto an end which brings the course of things to their point of departure.\n\nThis kind of internal activity of the living being is so striking, that\nnot only does it serve us to differentiate the living being from the\ninert body, but it gives rise to the illusion of a kind of internal\ndemon, vital force, manifested by the more or less apparent acts of the\nlife of relation, of the motricity, of the displacement, or by the less\nobvious acts of vegetative life.\n\n_Vital Phenomena regarded as a Reaction of the Ambient World. Their\nTwofold Conditioning._\u2014In reality, as the doctrine of energetics\nteaches us, the phenomena of vitality are not the effect of a purely\ninternal activity. They are a reaction of the environment. \u201cThe idea\nof life,\u201d says Auguste Comte, \u201cconstantly assumes the necessary\ncorrelation of two indispensable elements:\u2014an appropriate organism and\na suitable environment. It is from the reciprocal action of these two\nelements that all vital phenomena inevitably result.\u201d The environment\nfurnishes the living being with three things:\u2014its matter, its energy,\nand the exciting forces of its vitality. All vital manifestation\nresults from the conflict of two factors: the extrinsic factor which\nprovokes its appearance; the intrinsic factor, the very organization\nof the living body, which determines its form. Bichat and Cuvier saw\nin the phenomena of life the exclusive intervention of a principle of\naction entirely internal, checked rather than aided by the universal\nforces of nature. The exact opposite is true. The protozoan finds the\nstimuli of its vitality in the aquatic medium which is its habitat.\nThe really living particles of the metazoan\u2014that is to say, its\ncells, its anatomical elements\u2014meet these stimuli in the lymph, in\nthe interstitial liquids which bathe them and which form their real\nexternal environment.\n\nAuguste Comte thoroughly understood this truth, and has clearly\nexpressed it in the passage we have just quoted. Claude Bernard has\nfully developed it and given it its classical form.\n\nIn order to manifest the phenomena of vitality, the elementary being,\nthe protoplasmic being, requires from the external world certain\nfavourable conditions; these it finds there, and they may be called the\nstimuli, or extrinsic conditions of vitality. This being possesses no\ninitiative or spontaneity in itself, it has only a faculty of entering\ninto action when an external stimulus provokes it. This subjection of\nthe living matter is called _irritability_. The term expresses that\nlife is not solely an internal attribute, but an internal principle of\naction.\n\n\n \u00a7 1. EXTRINSIC CONDITIONS.\n\n\n_Extrinsic Conditions._\u2014By showing that every vital manifestation\nresults from the conflict of two factors: the extrinsic or\nphysico-chemical conditions which determine its appearance, and the\nintrinsic or organic conditions which regulate its form, Claude\nBernard dealt a mortal blow at the old vitalist theories. For he has\nnot only asserted the close dependence of the two kinds of factors,\nbut he has shown them in action in most physiological phenomena. The\nstudy of the extrinsic or physico-chemical conditions necessary to\nvital manifestations teaches us our first truth\u2014namely, that they\nare not infinitely varied as might be supposed. They present, on the\ncontrary, a remarkable uniformity in their essential qualities. The\nfundamental conditions are the same for the animal or vegetable cells\nof every species. They are four in number:\u2014_moisture_, the air, or\nrather _oxygen_, _heat_, and a certain _chemical constitution_ of the\nmedium, and the last condition, the enunciation of which seems vague,\nbecomes more precise if we look at it a little closer. The chemical\nconstitution of media favourable to life, the media of culture, obeys\nthree general laws. It is the knowledge of these laws which formerly\nenabled Pasteur, Raulin, Cohn, and Balbiani to provide the media\nappropriate to the existence of certain relatively simple organisms,\nand thus to create an infinitely valuable method for the study of\nnutrition, etc.,\u2014namely, the _method of artificial cultures_, numerous\ndevelopments of which have been shown us by microbiology and physiology.\n\n_The Optimum Law._\u2014It has been said, and it is more than a play on\nwords, that the conditions of the vital medium were the conditions\nof the _juste milieu_. Water is wanted, there must not be too much or\ntoo little. Oxygen is necessary, and also in certain proportions. Heat\nis required, and for that, too, there is an optimum degree. Certain\nchemical compounds are needed and, in this respect too, there must also\nbe _optima_ proportions.\n\nWater is a constituent element of the organisms. They contain fixed\nproportions for the same tissue, proportions varying from one tissue to\nanother (between 2\u22153 and 9\u221510). The cell of a living tissue requires\naround it an aqueous atmosphere, formed by the different juices of the\norganism, the interstitial liquids, the blood, and the lymph. We are\ndeceived by appearances when we distinguish between aerial, aquatic,\nand land-dwelling animals, and when we speak of the air, the water,\nand the land as their natural environment. If we go to the bottom\nof things, and fix our attention on the real living unities, on the\ncells of which the organism is composed, we shall find around them\nthe juices, rich in water, which are their real environment. If these\njuices are diluted or concentrated the least in the world, life stops.\nThe cell, the whole animal, falls into a state of latent life, or\ndies. \u201cAll living beings are aquatic,\u201d said Claude Bernard. \u201cBeings\nthat live in the air are in reality wandering aquariums,\u201d said another\nphysiologist. \u201cNo moisture, no life,\u201d wrote Preyer. The environment\nmust contain water, but it must contain it in certain proportions. In\nthe higher animals there is a mechanism which works automatically to\nkeep at a constant level the quantity of water in the blood. Researches\non the lavage of the blood (A. Dastre and Loye) have clearly shown\nthis.\n\nOxygen is also necessary to life. It is the _pabulum vit\u00e6_. But the\ndiscovery of the beings called by Pasteur _anaerobia_ appears to\ncontradict this statement. Pfeffer, the illustrious botanist, was\ncertain, in 1897, that the dogma of the necessity of oxygen no longer\nheld good. This is no longer tenable. In 1898 Beijerinck carried out\nmost careful researches on anaerobia said to have been cultivated in a\nvacuum, such as the _bacteria of tetanus_ and the _septic vibrion_; or\non those to which oxygen seems to be a poison, such as the _butyric_\nand the _butylic ferments_, the anaerobia of putrefaction, the reducing\nspirilla of the sulphates. All use free oxygen. They consume very\nlittle it is true; they are micro-aerobia. The other organisms, on\nthe contrary, need more. They are macro-aerobia or simply _aerobia_.\nBesides, if the so-called anaerobia take little or no free oxygen, it\nmatters little. They take the oxygen in combination. It may be said\nwith L. Errera that they have an affinity for oxygen, for they extract\nit from its combinations, and that \u201cthey are so well adapted to this\nmode of existence that life in the open air being too easy no longer\nsuits them.\u201d There are for the different animal species different\noptima of oxygen.\n\nLiving beings require a certain amount of heat. Life, which could not\nhave existed on the globe when it was incandescent, will not be able to\nexist when it is frozen. For each organism and each function there is a\nmaximum and a minimum of temperature compatible with activity. There is\nalso an optimum. For instance, the optimum is 29\u00b0 C for the germination\nof corn.\n\nThe condition of the optimum exists in the same way for the chemical\ncomposition of the vital medium\u2014and for the other ambient physical\nconditions, such as atmospheric pressure.\n\nIt is therefore a law of _universal_ scope, a regulating law, as it\nwere, of life. Life is a function of extrinsic variables, water, air,\nheat, the chemical composition of the medium, and pressure. \u201cEvery\nvital phenomenon begins to be produced, starting from a certain\nstage of the variable (minimum), becomes more and more vigorous as\nit increases up to a determinate value (optimum), weakens if the\nvariable continues to increase, and disappears when it has reached\na certain limiting value (maximum).\u201d This law, proved by Sachs, the\nGerman botanist, in 1860, apropos of the action of temperature on the\ngermination of plants, by Paul Bert in 1875, apropos of the action of\noxygen and of atmospheric pressure on animals, and already formulated\nat that time by Claude Bernard, was illustrated by Leo Errera in 1895.\nIt is a law of moderation. It expresses La Fontaine\u2019s \u201c_rien de trop_\u201d\nTerence\u2019s \u201c_ne quid nimis_,\u201d the \u03bc\u03b7\u03b4\u1f72\u03bd \u1f04\u03b3\u03b1\u03bd of Theognis, and the\nbiblical phrase \u201c_omnia in mensura et numero et pondere_.\u201d L. Errera\nsees the profound cause of this optimum law in the properties of the\nliving protoplasm, which are mean properties. It is semi-liquid. It is\ncomposed of albuminoid substances, which can stand no extremes either\nfrom the physical or from the chemical points of view.\n\n\n \u00a7 2. INTRINSIC CONDITIONS. THE LAW OF THE CONSTITUTION OF ORGANS AND\n APPARATUS.\n\n\n_Law of the Constitution of Organs and Apparatus._\u2014If we consider\nmore highly organized beings, the influence of the intrinsic\nconditions appears quite as clearly. As we have seen, this is so that\nthe requisite fundamental materials may be spent by each element in\nsuitable proportions,\u2014water, chemical compounds, air, and heat,\u2014that\norgans may be added to organs, and that apparatus may be set to work in\ncomplex structures. Why a digestive apparatus? To prepare and introduce\ninto the internal medium liquid materials which are necessary to\nlife. Why a respiratory apparatus? To impart the vital gas necessary\nto the cells, and to expel the gaseous excrement, the carbonic acid\nwhich they reject. Why a circulatory apparatus? To transport and renew\nthis medium throughout. The apparatus, the functional wheels, the\nvessels, the digestive and respiratory mechanisms do not exist for\nthemselves, like the random sketches of an artistic nature. They exist\nfor the innumerable anatomical elements which people the economy.\nThey are arranged to assist and more rigorously to regulate cellular\nlife with respect to the extrinsic conditions which it demands. They\nare, in the living body, as in civilized society, the manufactories\nand the workshops which provide for the different members of society\ndress, warmth, and food. In a word, the _law of the construction of\norganisms_ or of the _bringing to perfection of an organism_ is the\nsame as the law of cellular life. It is otherwise suggestive as the\nlaw of _division of physiological labour_ formerly enunciated by Henry\nMilne-Edwards; and in every case it has a more concrete significance.\nFinally, it brings the organic functional activity into relation with\nthe conditions of the ambient medium.\n\n_How Experiment acts on the Phenomena of Life._\u2014 The two orders of\nconditions, the one provided by the being itself, the other by external\nagents, are equally indispensable\u2014and therefore of equal importance or\ndignity. But they are not equally accessible to the experimentalist.\nIt is not easy to exercise on the organization direct and measurable\nactions. On the contrary, the physical conditions are in the hands\nand at the discretion of the experimenter. By them he may reach the\nvital manifestations as they appear, stimulate or check them, defer\nor precipitate them. Thus, for instance, the physiologist suspends\nor re-establishes at his will full vital activity in a multitude of\nreviviscent or hibernating beings, such as grains, the infusoria\ncapable of _encystment_, the vibrio, the tardigrade, the cold-blooded\nanimals, and perennial plants.\n\nThe ambient world therefore furnishes to the animal and to the\nvegetable, whole or fragmentary, those materials of its organization\nwhich are at the same time the stimuli of its vitality. That is to say,\nthe vital mechanism would be a dormant and inert mechanism if nothing\nin the surrounding medium could provoke it to action or give it a\ncheck. It would be a kind of steam engine without coal and fire.\n\nLiving matter, in other words, does not possess real spontaneity. As I\nhave shown elsewhere, the law of inertia which it is supposed it obeys\nwith inert bodies is not special to them. It is applied to the living\nbodies whose apparent spontaneity is only an illusion contradicted by\nphysiology as a whole. All the vital manifestations are responses to a\nstimulus of acts provoked, and not of spontaneous acts.\n\n_Generalization of the Law of Inertia in Living Bodies.\nIrritability._\u2014In fact, vulgar prejudice opposes this view. The\nopinion of the average man distrusts it. It applies the law of inertia\nonly to inert matter. This is because the vital response does not\nalways immediately succeed the external stimulus, and is not always\nproportional to it. But it is sufficient to have seen the flywheel of a\nsteam engine to understand that the restitution of a mechanical force\ncannot be instantaneous. It is sufficient to have had a finger on the\ntrigger of a firearm to know that there is no necessary proportion\nbetween the intensity of the stimulus and the magnitude of the force\nproduced. Things happen in the living just as in the inert machine.\n\nThe faculty of entering into action when provoked by an external\nstimulus has received, as we have said, the name of _irritability_.\nThe word is not used of inert matter. However, the condition of the\nlatter is the same. But there is no need to affirm its irritability,\nbecause no one denies it. We know perfectly well that brute matter\nis inert, that all the manifestations of activity of which it is the\ntheatre are provoked. Inertia is for it the equivalent of irritability\nin living matter. But while it is not necessary to introduce this idea\ninto the physical sciences, where it has reigned since the days of\nGalileo, it was, on the contrary, necessary to affirm it in biology,\nprecisely because it was in biology that the opposing doctrine of vital\nspontaneity ruled supreme.\n\nSuch was the view held by Claude Bernard. He never varied on this\npoint. _Irritability_, said he, is the property possessed \u201cby every\nanatomical element (that is to say, the protoplasm which enters into\nits constitution) of being stimulated into activity and of reacting\nin a certain manner under the influence of the external stimuli.\u201d He\ncould not claim that this was a distinguishing characteristic between\nliving bodies and brute bodies, and that all the less because he always\ntried to efface on this point the distinctions which were current in\nhis time, and which were established by Bichat and Cuvier. And so also\nLe Dantec does not seem to have thoroughly grasped the ideas of the\ncelebrated physiologist on this point when he asserts, as if he were\nthereby contradicting the opinion of Claude Bernard and his school,\nthat irritability is not something peculiar to living bodies.[17]\n\n [17] These ideas are clearly brought to light in a series of articles\n in the _Revue Philosophique_, published in 1879 under the title of \u201cLa\n probl\u00e8me physiologique de la vie,\u201d and endorsed by A. Dastre in his\n commentary on the _Ph\u00e9nom\u00e8nes communs aux animaux et aux plantes_.\n\n\n\n\n CHAPTER V.\n\n THE SPECIFIC FORM. ITS ACQUISITION. ITS REPARATION.\n\n \u00a7 1. Specific form not special to living beings\u2014Connected with the\n whole of the material conditions of the body and the medium\u2014Is it a\n property of chemical substance?\u2014\u00a7 2. Acquisition and re-establishment\n of the specific form\u2014Normal regeneration\u2014Accidental regeneration in\n the protozoa and the plastids\u2014In the metazoa.\n\n\n \u00a7 1. THE SPECIFIC FORM.\n\n\n_The Specific Form is not Peculiar to Living Beings._\u2014The position of\na _specific form_\u2014the acquisition of this typical form progressively\nrealized\u2014the re-establishment when some accident has altered it\u2014these\nare the features which we consider distinctive of living beings, from\nthe protophytes and the lowest protozoa to the highest animals. Nothing\ngives a better idea of the unity and the individuality of the living\nbeing than the existence of this typical form. We do not mean, however,\nthat this characteristic belongs to the living being alone, and is by\nitself capable of defining it. We repeat that this is not a case with\nany characteristic. In particular the _typical form_ belongs to crystal\nas well as to living beings.\n\n_The Specific Form depends on the sum of Material Conditions of the\nBody and the Medium._\u2014The consideration of mineral bodies shows us\nform dependent on the physico-chemical conditions of the body and the\nmedium. The form depends mainly on physical conditions in the cases\nof a drop of water falling from a tap, of the liquid meniscus in a\nnarrow tube, of a small navel-shaped mass of mercury on a marble slab,\nof a drop of oil \u201cemulsioned\u201d in a solution, and of the metal which\nis hardened by hammering or annealed. In the case of crystals the\nform depends more on chemical conditions. It is crystallization which\nhas introduced into physics the idea that has now become a kind of\npostulate\u2014namely, that the specific form is connected with the chemical\ncomposition. However, it is sufficient to instance the dimorphism\nof a simple body, such as sulphur, sometimes prismatic, sometimes\noctahedric, to realize that substance is only one of the factors of\nform, and that the physical conditions of the body and of the medium\nare other factors quite as influential.\n\n_Is the Specific Form a Property of the Chemical Substance?_\u2014How much\ntruer this restriction would be if we consider, instead of a given\nchemical compound, an astonishingly complex mixture, such as protoplasm\nor living matter, or the more complex organism still\u2014the cell, the\nplastid.\n\nAre there not great differences between the substance of the cellular\nprotoplasm, or cytoplasmic substance, and that of the nucleus? Should\nwe not distinguish in the former the hyaloplasmic substance; the\nmicrosomic in the microsomes; the linin between its granulations; the\ncentrosomic in the centrosome; the archoplasmic in the attraction\nsphere; not to mention the different leucins, the vacuolar juice, and\nthe various inclusions? And in the nucleus must we not consider the\nnuclear juice, the substance of the chromosomes, and that of the\nnucleoles? And is not each of these probably a very complex mixture?\n\nHowever, it is to this mixture that we attribute the possession\nof a form, in virtue of and by extension of the principles of\ncrystallization, which definitely teach us that these mixtures cannot\nhave form; that form is the attribute of pure bodies, and is only\nobtained by the separation of the blended parts\u2014_i.e._, by a return\nto homogeneity. There are therefore very good reasons for hesitating\nbefore we transfer the absolute principle of the dependence between\nchemical form and composition, as some philosophical biologists have\ndone, from the physical sciences\u2014where it is already subject to serious\nrestrictions\u2014to the biological sciences.\n\nLe Dantec, however, has made this principle the basis of his biological\nsystem. He therefore finds in the crystal the model of the living\nbeing. He thus gives a physical basis to life.\n\nIs it a question in this system of explaining this incomprehensible,\nthis unfathomable mystery, which shows the egg cell attracting to\nitself materials from without and progressively building up that\namazing structure which is the body of the animal, the body of a\nman, of any given man, of Primus, for example? It is said that the\nsubstance of Primus is specific. His living substance is his own,\nspecial to him; and that, too, from the beginning of the egg to the end\nof its metamorphosis. It only remains to apply to this substance the\npostulate, borrowed from crystallography, of the absolute dependence\nof the nature of substance on the form it assumes. The form of the\nbody of the animal, of the man, of Primus, is the crystalline form of\ntheir living substance. It is the only form of equilibrium that this\nsubstance can assume under the given conditions, just as the cube is\nthe crystallized form of sea salt, the only state of equilibrium of\nchloride of sodium in slowly evaporated sea water. Thus the problem\nof the living form is reduced to the problem of the living substance,\nwhich seems easier; and at the same time the biological mystery is\nreduced to a physical mystery. It is clear that this way of looking\nat things simplifies prodigiously\u2014and, we must add, simplifies far\ntoo much\u2014the obscure problem of the relation of form to substance,\nsimultaneously in the two orders of science. This may be summed up in a\nsingle sentence: There is an established relation between the specific\nform and the chemical composition: the chemical composition _directs_\nand implies the specific form.\n\nWe need not now examine the basis of this opinion. If it is nothing but\na verbal simplification, a unification of the language applied to the\ntwo orders of phenomena, it implies an assimilation of the mechanisms\nwhich realize them. To the organogenic forces which direct the\nbuilding up of the living organisms it brings into correspondence the\ncrystallogenic forces which group, adjust, equilibrate, and harmonize\nthe materials of the crystal.\n\nWhen it is a question of the application of a principle such as\nthis, in order to test its legitimacy we must always return to the\nexperimental foundations. Let us imagine, for example, a simple body,\nsuch as sulphur, heated and brought to a state of fusion\u2014that is to\nsay, homogeneous, isotropic, in an undisturbed medium the only change\nin which will be a very gradual cooling down. These are the typical\ncrystallogenic conditions. The body would take a given crystalline\nform. It is from experiments such as this that we derive the idea of _a\nspecific form connected with a chemical constitution_.\n\nBut in drawing this conclusion our logic is at fault. The real\ninterpretation suitable to this case, as in all others, is that the\nspecific form is suitable to the substance, and also to the physical,\nchemical, and mechanical conditions in which it is placed. And the\nproof is that this same substance, sulphur, which takes the prismatic\nform immediately after fusion, will not retain that form, but will pass\non to the quite different octahedral form.\n\nIt is so with the specific form of the living being\u2014that is to say,\nwith the assemblage of its constituent materials co-ordinated in a\ngiven system\u2014in a word, with its organization. This is suitable to its\nsubstance, and to all the material, physical, chemical, and mechanical\nconditions in which it is placed. This form is the condition of\nmaterial equilibrium corresponding to a very complex situation, to a\nsum of given conditions. The chemical condition is only one of these.\nAnd further, it is hardly proper to speak of a \u201cchemical substance\u201d\nwhen we refer to an astonishingly complex mixture which is in addition\nvariable from one point to the other of the living body. When we thus\nreduce phenomena to their original signification, false analogies\ndisappear. To say with Le Dantec that the form of the greyhound is\nthe condition of equilibrium of the \u201cgreyhound chemical substance\u201d is\nsaying much; and too much, if it means that the body of the greyhound\nhas a substance which behaves in the same way as homogeneous, isotropic\nmasses like melted sulphur and dissolved salt. It were better to say\nmuch less, if it means, as it will in the minds of the physiologists,\nthat the body of the greyhound is the condition of equilibrium of a\nheterogeneous, anisotropic, material system, subjected to an infinite\nnumber of physical and chemical conditions.\n\nThe idea of connecting form, and by that we mean organization, with\nchemical composition did not arise in the minds of chemists or\nphysiologists. Both have expressed themselves very clearly on this\npoint.\n\n\u201cWe must distinguish,\u201d said Berthelot, \u201cbetween the formation of the\nchemical substances, the assemblage of which constitutes organized\nbeings, and the formation of the organs themselves. This last problem\ndoes not come into the domain of chemistry. No chemist will ever\nclaim to have formed in his laboratory a leaf, a fruit, a muscle, or\nan organ.... But chemistry has a right to claim that it forms direct\nprinciples\u2014that is to say, the chemical materials which constitute the\norgans.\u201d And Claude Bernard in the same way writes:\u2014\u201cIn a word, the\nchemist in his laboratory, and the living organism in its apparatus,\nwork in the same way, but each with its own tools. The chemist can make\nthe products of the living being, but he will never make the tools,\nbecause they are the result of organic morphology.\u201d\n\n\n \u00a7 2. THE ACQUISITION AND RE-ESTABLISHMENT OF THE SPECIFIC FORM.\n\n\n_Acquisition of the Typical Form._\u2014The acquisition of the typical\nform in the living being is the result of ontogenic work which cannot\nbe examined here. In the elementary being, the plastid, this work is\nblended with the work of nutrition. It is _directed nutrition_. It\nconsists of a simple increase from the moment the element is born by\nthe division of an anterior element, and of a necessarily restricted\ndifferentiation. It is a rudimentary embryogeny. In the complex being,\nmetazoan or metaphyte, the organism is constituted, starting from the\negg, by the growth, by the bipartition of the elements, and their\ndifferentiation, accomplished in a certain direction and in conformity\nwith a given plan. This, again, is directed nutrition, but here the\nembryogeny is complex. The directing plan of operations is no doubt\nthe consequence of the material conditions realized each moment in the\norganism.\n\n_Normal Regeneration._\u2014Not only do living beings themselves\nconstruct their typical architecture, but they re-establish it\nand continually reconstitute it, according as accidents, or even\nordinary circumstances, tend to destroy it; in a word, they become\nrejuvenescent. This regeneration consists in the reformation of the\nparts that are altered or carried away in the normal play of life, or\nby the accidents which disturb its course.\n\nThus there is a _normal physiological regeneration_, which is, so to\nspeak, the prolongation of the ontogenesis\u2014_i.e._, of the work of\nformation of the individual. We have examples in the reconstitution\nof the skin of mammals\u2014in the throwing off of the epidermic products\nconstantly used up in their superficial and distal parts and\nregenerated in their deeply-seated parts; in the loss and the renewal\nof teeth at the first dentition and in certain fish in the fact of\nsuccessive dentitions; in the periodical renewal of the integument\nin the larv\u00e6 of insects, and in the crustace\u00e6; and finally in the\ndestruction and the neo-formation of the globules of the blood of\nvertebrates, of the glandular cells, and of the epithelial cells of the\nintestine.\n\n_Accidental Regeneration in Protozoa and Plastids._\u2014There is also an\n_accidental regeneration_ which more or less perfectly renews the parts\nthat are lost. This regeneration has its degrees, from the simple\ncicatrization of a wound to the complete reproduction of the part cut\noff. It is very unequally developed in zoological groups even when they\nare connected. In the elementary monocellular beings\u2014_i.e._, in the\nanatomical elements and in the protozoa,\u2014the experiments in merotomy,\n_i.e._, in _partial section_, enable us to appreciate the extent of\nthis faculty of regeneration. These experiments, inaugurated by the\nresearches of Augustus Waller in 1851, were repeated by Gruber in 1885,\ncontinued by Nussbaum in 1886, Balbiani in 1889, Verworn in 1891, and\nhave been reproduced by a large number of observers. They have shown\nthat the two fragments cicatrize, and are repaired, building up an\norganism externally similar to the primitive organism, but smaller.\nThe two new organic units do not, however, behave in the same way.\nThat which retains the nucleus possesses the faculty of regeneration,\nand of living as the primitive being lived. The protoplasmic fragment,\nwhich does not contain the nucleus, cannot rebuild this absent organ;\nand though it has functional activity in most respects, just as the\nnucleated fragment, yet it is distinguished from it in others of great\nimportance. The anucleated fragment of an infusorian behaves as the\nnucleated, and as the whole animal so far as the movements of the body,\nthe cilia, prehension of food, evacuation of f\u00e6ces, and the rhythmical\ncontraction of the pulsatile vesicules are concerned. But Balbiani\u2019s\nresearches in 1892 have shown us that secretion, complete regeneration,\nand the faculty of reproduction by fission can take place only in the\nnucleated fragment\u2014_i.e._, in the nucleus.\n\n_Accidental Reproduction in the Metazoa._\u2014Among multicellular beings\nthe faculty of reproduction is met with in the highest degree in\nplants, where we find it in the process of propagation by slips. In\nanimals it is the most marked in C\u0153lenterata. Trembley\u2019s experiments\nare a striking instance. We know that when the hydra is cut into\ntiny pieces it reproduces exactly as many complete beings. Among the\nworms, Planaria afford a similar example. Every fragment, provided its\nvolume is not less than a tenth of that of the whole, can reproduce\na complete, entire being. The snail can produce a large part of its\nhead, including the tentacles and the mouth. Among the Tritons and\nthe Salamanders the faculty of regeneration reproduces the limbs, the\ntail, and the eye. In the Frog family, on the contrary, the work of\nregeneration does not go beyond cicatrization, and it is the same with\nBirds and Insects.\n\nIt is really startling to see in a vertebrate like the Triton the stump\nof an arm with its fragment of humerus reproducing the forearm and\nthe hand in all their complexity, with their skeleton, blood vessels,\nnerves, and teguments. We say that the limb has _budded_, as if there\nwere a germ of it which develops like the seed of a plant, or as if\neach transverse portion of the limb, each slice, so to speak, could\nre-form the slice that follows.\n\nThe mechanism of generation and that of regeneration alike raise\nproblems of the highest importance. Does the part become regenerated\njust as it was formed at first? Does the regeneration repeat the\nontogeny? Is it true that a lost organ is never regenerated (the\nkidney for instance)? Does the symmetrical organ enjoy a compensating\nand hypertrophic development, as Ribbert has asserted? And further,\nif the organ be removed and transplanted to another position, can it\nbe grafted there, as Y. Delage maintains? These are very important\nquestions; but if we dwell upon them, we shall be diverted from our\nimmediate object. Our task is to look at these facts from the point\nof view of their significant and characteristic meaning in vitality.\nFlourens invoked on their behalf the intervention of vital forces,\n_plastic_ and _morphoplastic_. But, as we shall see later, these\nphenomena of cicatrization, of reparation, of regeneration, these more\nor less complete efforts for the re-establishment of the specific form,\nalthough they are found in all living beings in different degrees,\nare not exclusively confined to them. We find them again in some\nrepresentatives of the mineral world\u2014in crystals, for instance.\n\n\n\n\n CHAPTER VI.\n\n NUTRITION.\n\n FUNCTIONAL ASSIMILATION. FUNCTIONAL DESTRUCTION. ORGANIC DESTRUCTION.\n ASSIMILATING SYNTHESIS.\n\n The extreme importance of nutrition\u2014\u00a7 1. Effect of vital\n activity\u2014Destruction or growth\u2014Distinction between the living\n substance and the reserve-stuff mingled with it\u2014Organic\n destruction\u2014Destruction of reserve-stuff\u2014Destruction of living\n matter\u2014Growth of living matter\u2014\u00a7 2. The two categories of vital\n phenomena\u2014Foundations of the idea of functional destruction\u2014The two\n kinds of phenomena of vitality\u2014Criticism of Claude Bernard\u2014Current\n views\u2014Criticism of Le Dantec\u2019s new theory of life.\u2014\u00a7 3. Correlation of\n the two kinds of vital facts\u2014Law of connection\u2014Contradictions in the\n new theory.\u2014\u00a7 4. The characteristics of nutrition\u2014Its definition\u2014Its\n permanence\u2014Erroneous idea of the vital vortex\u2014Formative assimilation\n of reserve-stuff\u2014Formative assimilation of protoplasm\u2014Death, real and\n apparent.\n\n\n_The Immense Importance of Nutrition._\u2014We now come to the important\nfeature of vitality. All other characteristics of living matter, its\nunstable equilibrium, its chemical and anatomical organization, the\nacquisition and the maintenance of a typical form, are only secondary\nproperties, so to speak, subordinate with reference to _nutrition_.\nGeneration itself is only a mode. _Nutrition_ is the essential\nattribute of life. It is life itself.\n\nBefore we define it a few preliminary explanations are necessary.\n\nThe most striking thing in living matter is its _growth_. An animal, a\nvegetable, is something which is first more or less minute, and which\ngrows. Its characteristic is to expand\u2014from the spore, the seed, the\nslip, the egg\u2014it grows.\n\nWhether we are dealing with a cellular element, a plastid, or a complex\nbeing, their condition is the same in this respect. No doubt when the\nanimal or plant has reached a certain stage of development its growth\nis stopped, and for a more or less lengthy period it remains in the\nadult stage, in what seems to be equilibrium. But even then there is no\ncheck in the manufacture of living matter; there is only a compensation\nbetween its production and its destruction.\n\nIt is important to reduce to order the ideas on this important subject,\nwhich at present are confused, inconsistent, and contradictory. In\nbiology grievous confusion reigns.\n\n\n \u00a7 1. EFFECT OF THE VITAL ACTIVITY. DESTRUCTION OR GROWTH?\n\n\n_Distinction between the Living Substance and the Reserve-stuff mingled\nwith it._\u2014The physiology of nutrition has given rise to a vast body\nof research during the last half-century. Physiological schools,\nmasters and pupils, such as the school at Munich under Voit and\nPettenkofer, Pfl\u00fcger\u2019s at Bonn, Rubner\u2019s, and those of Zuntz and von\nNoorden at Berlin, and a large number of zootechnical and agricultural\nlaboratories through the whole world have for years past been engaged\nin analyzing ingesta and egesta, in drawing up schedules of nutrition,\nin order to determine the course of decomposition and reconstitution of\nthe living material.\n\nIf I were asked what, in my opinion, is the most general result of\nall this labour, I would reply that it has affirmed and corroborated\nthe important distinction which must be drawn between _living\nsubstance, properly so called_, and _reserve-stuff_. The latter,\nthe _reserve-stuff_ of albuminoids, carbohydrates, and fats, are so\nintimately intermingled with the living substance that they are in most\ncases very difficult to distinguish from it.\n\n_Organic Destruction._\u2014A second point, which is placed equally\nbeyond doubt, is that the vital functional activity is accompanied\nby a destruction of the immediate principles of the organism, in the\ndirection of their simplification. This functional destruction cannot\nbe doubted in the case of differentiated organs in which the functional\nactivity is evident, intermittent, and in some measure distinct from\nthe other vital phenomena which take place in them. For example, in the\ncase of contracting muscles the respiratory carbonic acid and urinary\ncarbon are the irrefutable proofs of this destruction: weak in repose,\nabundant during activity, and in proportion to it. There can be no\ndoubt on this point. The truth laid down by Claude Bernard under the\nname of the _law of functional destruction_ has been doubly consecrated\nby experiment and theory. According to the energetic theory, in fact,\nmechanical and thermal energies manifested in the vital functional\nactivity can only have their source in the chemical energy set free by\nthe destruction of the immediate principles of the organism, reduced\nto a lower degree of complexity.\n\n_Destruction of Reserve-stuff._\u2014But now the disagreement begins. What\nare these decomposed, destroyed principles? Do they belong to the\ncellular reserve-stuff or to the living matter properly so called?\nThere is no doubt that most of them belong to the reserve-stuff.\nFor example, this is especially true of glycogen, which is consumed\nin muscular contraction just as coal is consumed in the furnace of\nthe locomotive; and glycogen is a reserve-stuff of muscle. These\nreserve-stuffs destroyed in the functional activity can be built up\nagain only during repose.\n\nBut it is not yet certain whether the living matter itself, the\nactive protoplasm, the muscular protoplasm, takes part in this\ndestruction, whether it provides it with elements. Experiments have\nproved contradictory. Experimenters have isolated the nitrogenous\nwastes (urea) after muscular labour, and they have compared them with\nthe wastes of the period of repose. These nitrogenous wastes bear\nwitness to the destruction of albuminoid substances, and the latter are\nthe constituent principles of living matter. If\u2014under conditions of\nsufficient alimentation\u2014the muscular functional activity involves more\nnitrogenous waste, _i.e._, a greater destruction of albuminoids, it\nmight be supposed that the living material properly so called has been\nused up and destroyed for its own purposes. (And here again there might\nbe a reserve-stuff of albuminoids, distinct from the living protoplasm\nitself, and more or less incorporated with it.)\n\nBut experiment so far has not given decisive results. The latest\nexperimental researches, such as those of Igo Kaup, of Vienna, which\ndate from 1902, tell us as uncertain a tale as their predecessors.\nThe increase in the destruction of albumen has not been constant; the\nconditions of the observations do not justify our making an assertion\neither _pro_ or _con_.\n\n_Destruction of Living Matter._\u2014As no certain answer is supplied by\nexperiment, theory intervenes and gives two conflicting answers. The\nmajority of physiologists are inclined to believe in _the destruction\nof the living substance as the result of its own functional activity_.\nThe functional activity would therefore destroy not only the\nreserve-stuff, but also the protoplasmic material. This is the current\nview. Only this opinion is strongly challenged by the positive teaching\nof science. It is certain that this material, in the muscle, is but\nlittle attacked, if it is attacked at all. We have seen above that the\nphysiologists, with Pfl\u00fcger and Chauveau, are agreed on this point.\nThe vital functional activity in particular is destructive to the\nreserve-stuffs. It does not destroy them much; it destroys the organic\nmaterial still less. Both would be repaired in functional repose.\n\n_Growth of Living Matter._\u2014The second assertion is diametrically\nopposed to this. Not only, says Le Dantec, is the muscle not destroyed\nin the functional activity, but it grows. Contrary to universal\nopinion, the protoplasmic material increases by activity, and it is\ndestroyed in repose. There would thus be a general law\u2014_the law of\nfunctional assimilation_. \u201cA cell of brewers\u2019 yeast when introduced\ninto a sugared must makes this must ferment, and at the same time, so\nfar from destroying it, it increases it. Now, the fermentation of the\nmust is exactly the same as the functional activity of the yeast.\u201d It\nis, says the same author, a mistake to believe that the phenomena of\nfunctional activity, of _vital activity_, only takes place at the price\nof organic destruction. Here, then, are these two competing views.\nThey are not so very far apart as a matter of fact, since the question\nat issue is one of deciding between a slight destruction and a slight\ngrowth, but theoretically they are strongly opposed. Moreover, they are\narbitrary, and _experiment_ has not decided between them.\n\n\n \u00a7 2. THE TWO CATEGORIES OF VITAL PHENOMENA.\n\n\n_Foundation of the Idea of Functional Destruction. Claude Bernard._\u2014The\ndoctrine of functional destruction has been laid down with remarkable\npower by Claude Bernard. But the terms in which he has expressed it\nin a measure betray the thoughts of the great physiologist, or, at\nany rate, overstep the immediate fact he had in view. \u201cThe phenomena\nof destruction are very obvious. When movement is produced, when the\nmuscle contracts, when volition and sensibility are manifested, when\nthought is exercised, when the gland secretes, then the substance\nof the muscles, of the nerves, of the brain, of the glandular\ntissue, becomes disorganized, destroyed, and consumed. So that every\nmanifestation of a phenomenon in the living being is necessarily\nconnected with an organic destruction.\u201d To Claude Bernard organic\ndestruction is a truth. To Le Dantec it is an error. Which is right?\nClearly Claude Bernard. He bases his conviction on the analyses of\nthe materials excreted in the process of physiological work. The\nexcreta bear witness to a certain organic demolition. Generalizing\nthis teaching of experiment the illustrious biologist divined the\nfundamental law of energetics before the idea of energetics had made\nmuch way in France. Every act which expends energy, which produces heat\nor motion, any manifestation whatever that may be looked upon as an\nenergetic transformation, necessarily expends energy, and that energy\nis borrowed from the substance of the organism. These substances are\nsimplified, broken up, and destroyed. Now the functional activity of\nthe muscle produces heat and movement in warm-blooded as well as in\ncold-blooded animals. The functional activity of the glands produces\nheat, as has been shown by the celebrated experiments of C. Ludwig on\nthe salivary secretion, and as is also shown by the study of thermal\ntopography in the vertebrates. The functional activity of the nerves\nand the brain produces a slight quantity of electricity and heat, as\nmost observers have agreed. The functional activity of the electrical\nand of the photic apparatus also expends energy. Finally, the eye\nwhich receives the photic impression destroys the purple matter of the\nretina, and that purple matter, as we well know, is recuperated in\nthe dark during the repose of the organ. Everything that is expressed\nobjectively, everything that is a phenomenon in the living being\u2014with\nthe exception of growth and formation, which are generally slow\nphenomena, and of which we can only get an idea by the comparison\nof successive states\u2014all these energetic manifestations suppose a\ndestruction of organic matter, a chemical simplification, the source\nof the energy manifested. And that is why material destruction does\nnot merely coincide with functional activity, but is its measure and\nexpression.\n\n_The Two Kinds of Phenomena of Vitality._\u2014Another point on which\nClaude Bernard is right and his opponent is wrong is not less\nfundamental. What are we to understand by functional phenomena?\nThis is the very point at issue. Now, in the mind of physiologists,\nthis expression has a perfectly definite meaning. It is not so with\nLe Dantec. Physiologists who have studied animals rather high in\norganization\u2014in which the differentiation of phenomena enables us to\ngrasp the fundamental distinction\u2014have readily recognized that the\nphenomena of living beings are divided into two categories. There are\nsome which are intermittent, alternative, which take place, or grow\nstronger at certain moments, but which cannot be continuous\u2014they are\nthe _functional acts_; there are others in which this characteristic of\nexplosives, energetic expenditure and intermittence, do not appear\u2014they\nare, in general, the _nutritive acts_. The muscle which contracts shows\nfunctional activity. It has an activity and a repose. During this\napparent repose we must not say that it is dead; it has a life, but\nthat life is obscure as far as the salient fact of functional movement\nis concerned. The salivary gland which throws up waves of saliva when\nthe food is introduced and masticated in the mouth, or when the chord\nof the tympanum is at work, is in a state of functional activity; this\nis the salient phenomenon. But before, though nothing, absolutely\nnothing, was flowing through the glandular canal, yet the gland was\nnot reduced to the condition of a dead organ: it was living a more\nobscure, a less evident life. The microscopical researches of K\u00fchne,\nLea, and Langley, now universally verified, show us that during this\ntime of apparent repose the cells were loading up their granulations\nand getting ready the materials of secretion, as just now the muscle\nat rest was accumulating glycogen and the reserve-stuff which are to\nbe expended and destroyed in contraction. Similarly, with regard to\nthe functional activity of the other glands, of the brain, etc. Claude\nBernard was, therefore, perfectly right, when he took as his model\nthe chemists who distinguished between exothermic and endothermic\nreactions, and who classed the phenomena of life into two great\ndivisions: those of functional activity, and those of functional repose.\n\n1st. _The phenomena of functional activity_ \u201care those which \u2018leap to\nthe eyes,\u2019 and by which we are inclined to characterize life. They are\nconditioned by the effects of wear and tear, of chemical simplication,\nand of the organic destruction which liberates energy.\u201d And it must\nbe so, because these functional manifestations expend energy. These\nphenomena, which are the most obvious, are also the least specific\nphenomena of vitality. They form part of the general phenomenality.\n\n2nd. The _phenomena_ which accompany _functional repose_ correspond to\nthe building up of the reserve-stuff destroyed in the preceding period,\nto the organizing synthesis. The latter remains \u201cinternal, silent,\nconcealed in its phenomenal expression, noiselessly gathering together\nthe materials which will be expended. We do not see these phenomena\nof organization directly. The histologist and the embryogenist alone,\nfollowing the development of the element or of the living being, sees\nthe changes and the phases which reveal this silent effort. Here is a\nstore of substance; there, the formation of an envelope or a nucleus;\nthere, a division or multiplication, a renewal.\u201d This type of phenomena\nis the only type which has no direct analogues: it is peculiar, special\nto the living being: what is really vital is this evolutive synthesis.\nLife is creation.\n\n_Criticism of Claude Bernard._\u2014All this is perfectly true. Thirty years\nof the most intensive scientific development have run by since these\nlines were written, and have not essentially changed the ideas therein\nexpressed. His work in its broad lines remains intact. Does that imply,\nhowever, that everything is perfect in detail and expression, and that\nthere is no reason for making it more precise or for giving it fresh\nform? No doubt this is not so. Although Claude Bernard contributed to\nestablish the essential distinction between the real living protoplasm\nand the materials of reserve-stuff which it contains, he has not drawn\na sufficiently clear distinction between what belongs to each of the\ncategories. He has not specified, in relation to organic destruction,\nwhat bearing it has on the organic materials of reserve-stuff.\nSometimes he uses the term \u201corganic destruction,\u201d which is correct, and\nsometimes \u201cvital destruction,\u201d which is of doubtful import. Further, he\nemploys an obscure and paradoxical formula to characterize the obvious\nbut nevertheless not specific phenomena of organic destruction, and he\nsays: \u201clife is death.\u201d\n\n_Current Views._\u2014Nowadays, if I may express a personal opinion on\nthis important distinction between functional activity and functional\nrepose, I should say that after having distinguished between the\ntwo categories of phenomena we must try to correlate them. We must\ntry to discover, for instance, what there is in common between the\nmuscle in repose and the muscle in contraction, and to perceive in the\n_muscular tonus_ a kind of bridge thrown between these two conditions.\nThe functional activity would be uninterrupted, but it would have\nits degrees of activity. The muscular tonus would be the permanent\ncondition of an activity which is capable only of being considerably\nraised or lowered. Similarly for the glandular functional activity;\nthe periods of charge must be connected with the periods of discharge.\nIn a word, following the constant path of the human mind in scientific\nknowledge, after having drawn the distinctions that are necessary to\nour understanding of things, we must obliterate them. After having\ndug our ditches we must fill them up again. After having analyzed we\nmust synthesize. The distinction between the phenomena of _functional\nactivity_ and the phenomena of _functional repose_ or _purely\nvegetative_ and nutritive _activity_, though only valid in the case of\na provisional and approximate truth, none the less throws light on the\nobscure regions of biology.\n\nThe succession of energy and repose, of sleep and awakening, is a\nuniversal law, or at least a very general law, connected with the laws\nof energetics. The heart, the lungs, the muscles, the glands, the brain\nobey in the most obvious manner this obligation of rhythmical activity.\nThe reason is clear. It is because the functional activity involves\nwhat is generally a sudden expenditure of energy, and this has to be\nreplaced by what is generally a slow process of reparation. Functional\nactivity is an explosive destruction of a chemical reserve which is\nbuilt up again more or less slowly.\n\n_Criticism of Le Dantec\u2019s \u201cNew Theory of Life.\u201d_\u2014Let us now examine the\nantithesis of Claude Bernard\u2019s views. There are evidently rudimentary\norganisms in which the differentiation of the two categories of\nphenomena is but little marked; in which, apart from the movement,\nit is impossible to recognize intermittent, functional activities\nclearly distinct from morphogenic activity. It is not in this domain\nof the indistinct that we must seek the touchstone of physiological\ndistinctions. Clearly, we must not choose these elementary plastids\nto test the doctrine of functional assimilation and functional\ndestruction. But is not this exactly what Le Dantec did when he began\nhis researches on brewers\u2019 yeast? When we try to examine things,\nwe must choose the conditions under which they are differentiated,\nand not those in which they are confused. And this is why, in the\nsignificant words of Auguste Comte, \u201cthe more complex living beings\nare, the better known they are to us.\u201d The philosopher goes still\nfarther in this direction, and adds \u201cdirectly it is a question of the\ncharacteristics of animality we must start from the man, and see how\nthose characteristics are little by little degraded, rather than start\nfrom the sponge and endeavour to discover how these characteristics are\ndeveloped. The animal life of the man assists us to understand the life\nof the sponge, but the converse is not true.\u201d\n\nWhen, moreover, we consider a vegetable organism such as yeast, which\nderives its energy, not from itself, not from the potential chemical\nenergy of its reserve-stuff, but directly from the medium\u2014that is to\nsay, from the potential chemical energy of the compounds which form\nits medium of culture,\u2014we then find ourselves in the worst possible\nsituation for the recognition of organic destruction. Further, it is\ndoubly wrong to assert that in so ill-chosen a type the functional\nphenomena do not result from an organic destruction\u2014for at first there\nare no very distinct functional phenomena here\u2014and, in the second\nplace, there certainly is organic destruction. The phenomena of the\nmorphogenic vitality detected in the yeast are the exact concomitants,\nor the results, of the destruction of an organic compound, which in\nthis case is sugar. The yeast destroys an immediate principle, and\nthis is the point of departure of its vital manifestations; only, it\nhas not, as a preliminary, clearly incorporated and assimilated this\nprinciple. When, therefore, the functional phenomena are effaced and\ndisappear, we none the less find phenomena of destruction of organic\ncompounds which are in a measure, a preface to the phenomena of growth.\nThis is what happens in the case of brewers\u2019 yeast: and here, again,\nthe two categories of facts exist. Once more, we find, in the first\nplace, the phenomena of destruction (destruction of sugar, reduced\nby simplification to alcohol and carbonic acid)\u2014phenomena which this\ntime no longer respond to obvious functional manifestations; and, in\nthe second place, the phenomena of chemical and organogenic synthesis,\ncorresponding to the growth of the yeast and the multiplication of its\nprotoplasm. The former are no longer detected, as we have just said, by\nstriking manifestations. However, it is not true that everything which\nis visible and which may be isolated outside the activity of the yeast\nis part of those phenomena. The boiling of the juice or the mash,\nthe heat given off by the copper, all this phenomenal apparatus is\nbut the consequence of the production of the carbonic acid and of its\nliberations\u2014_i.e._, the consequence of the act of destruction of the\nsugar. Here is organic destruction with its energetic manifestations!\n\nThis example of the life of brewers\u2019 yeast, of the saccharomyces,\nspecially chosen by Le Dantec as being absolutely clear and giving the\nbest illustration of his argument, contradicts him at every point. The\ngeneral thesis of this vigorous thinker is that we cannot distinguish\nbetween the two parts of the vital act, organic destruction, and\nassimilating synthesis; that these two acts are not successive; that\nthey give rise to phenomenal manifestations equally evident, apparent,\nor striking. Now, in the case of yeast, the phenomenon of destruction\nis clearly distinct from that of the assimilating synthesis which\nmultiplies the substance of the saccharomyces. In fact, the action is\nrealized by means of an alcoholic diastase manufactured by the cell;\nand B\u00fcchner succeeded in isolating this alcoholic ferment which splits\nup the sugar into alcohol and carbonic acid, and also _in vitro_ and\n_in vivo_, makes the vat boil and heats the liquid. All the yeast is at\nwork at once, says M. Dantec. No, and this is the proof.\n\nAnd, further, Pasteur himself, who had shown the relation of the\ndecomposition of the sugar to the fact of the growth of the yeast and\nof the production of accessory substances such as succinic acid and\nglycerine, always referred to _correlation_ between these phenomena.\nThe destruction of the sugar is the _correlative_ of the life of the\nyeast. This was his favourite formula. It never entered his head\nthat there could be a confusion instead of a correlation, and that\nthere might be only one and the same act, the phases of which would\nbe indistinguishable. This unfortunate idea, which was fated to be so\nrapidly contradicted, is due to Le Dantec. Far from it being the case,\nPasteur had distinguished the _ferment function_ from the life of the\nyeast. According to him, the yeast may exist sometimes as a ferment and\nsometimes otherwise.\n\n\n \u00a7 3. CORRELATION OF TWO ORDERS OF VITAL FACTS.\n\n\nIt is this correlation between acts _distinct in themselves_ but\n_usually connected_ that was announced by Claude Bernard. And,\n_mirabile dictu_\u2014and this is the natural outcome of the perfect sanity\nof mind of this great physiologist\u2014it happens that not only Pasteur\u2019s\nresearches, but the development of a new science, Energetics, and\nB\u00fcchner\u2019s discovery lend support to his views, and that, too, in a\nfield where one would have thought they had no application. Le Dantec\nis wrong when he declares that these ideas only apply to vertebrates.\n\u201cIt is clear,\u201d he says on several occasions, \u201cthat the author has\nin view the metazoa and even the vertebrates.\u201d Well! no. All that\nis general, universally applicable, and universally true. So that\nthere are two orders of distinct phenomena energetically opposed and\ncertainly connected. We need only repeat Claude Bernard\u2019s own words\nquoted by Le Dantec in order to confute them.\n\n_Law of Connection of Two Orders of Vital Facts._\u2014\u201cThese phenomena [of\norganic destruction and of assimilating synthesis] are simultaneously\nproduced in every living being, in a connection which cannot be broken.\nThe disorganization or dissimilation uses up living matter [by this\nwe must understand the reserve-stuff, as will be seen later on in the\nquotation] in the organs _in function_: the assimilating synthesis\nregenerates the tissues; it gathers together the reserve-stuff which\nthe vital activity must expend. These two operations of destruction\nand renovation, inverse the one to the other, are absolutely connected\nand inseparable, in this sense at any rate, that destruction is\nthe necessary condition of renovation. The phenomena of functional\ndestruction are themselves the precursors and the instigators of\nmaterial regeneration, of the formative process which is silently going\non in the intimacy of the tissues. The losses are repaired as they take\nplace; and equilibrium being re-established as soon as it tends to be\nbroken, the body is maintained in its composition.\u201d\n\nIt is perfectly right and wise to say with Claude Bernard that the two\norders of facts are successive, and that one is normally the inciting\ncondition of the other. The possibility of the development of the yeast\nwhen fermentation fails, and the weakness of this development on the\nother hand under these conditions, are an excellent proof of this. The\none proves the essential independence of the two orders of facts, the\nother the inciting and provoking virtue of the first relatively to the\nsecond. The experimental truth is thus expressed with a minimum of\nuncertainty. We know the facts which led Le Dantec to formulate his\nlaw of functional assimilation\u2014namely, that the functional activity is\nuseful or indispensable to the growth of the organ; that the organs\nwhich are functionally active grow, and those which do not act\nbecome atrophied. We are only expressing the facts when we say that\nthe organic destructions that go on in the living being (whether at\nthe expense of its reserve-stuff or at the expense of its medium, or\nwhether it be even slightly at the expense of the plastic substance\nitself) are the antecedent, the inciting agent or the normal condition\nof the chemical and organogenic syntheses which create the new\nprotoplasm.\n\nOn the other hand, we are wrong if we hold with Le Dantec that\ninstead of two chemical operations there is only one, that which\ncreates the new protoplasm. The obvious destruction is neglected; it\nis deliberately passed over. He does not see that it is necessary to\nliberate the energy employed in the construction, by complication, of\nthis highly complex substance which is the new protoplasm. He really\nseems to have made up his mind not to analyze the phenomenon. If we\ndecline to admit that to the first act of functional destruction\nsucceeds a second, assimilation or organogenic synthesis, we are\nlooking at elementary beings, in which the succession cannot be\ngrasped, as we look on brewers\u2019 yeast. We not only mean that the\nmorphogenic assimilation results from the functional activity; we\nmean that it results from it directly, immediately, that it is the\nfunctional activity itself. Experiment tells us nothing of all this.\nIt shows us the real facts, the facts of the destruction of an organic\nimmediate principle, the sugar, and the fact that an assimilating\nsynthesis is the correlative of this destruction. Besides, if it is\nimpossible in examples of this kind to exhibit the succession, it is\nperfectly easy in beings of a higher order. It is, then, clearly seen\nthat the preliminary destruction of a reserve-stuff (and perhaps of\na small quantity of the living substance) precedes and conditions the\nformation of a greater quantity of this living matter\u2014in other words,\nthe growth of the protoplasm of the organ.\n\n_Contradictions in the New Theory._\u2014Moreover, these mistakes involve\nthose who make them in a series of inextricable contradictions. Here,\nfor example, is life; it is found, they say, in three forms:\u2014Life\nmanifested, or condition 1\u00ba; latent life, or condition 3\u00ba. So far\nthis is the classical theory; but they add a condition 2\u00ba, which\nis what might be called _pathological or incomplete life_. This\nis defined by the following characteristic:\u2014That its functional\nphenomena are identical with those in the first form, but that they\nare not accompanied by assimilation and by protoplasmic growth, But\nsince, they say, growth is the chemical consequence of the functional\nactivity, since it is so to speak its metabolic aspect, since it is\nconfused with it, and inseparable from it, by the argument\u2014then it is\ncontradictory and logically absurd to speak of condition 2\u00ba. It would\nbe acknowledging in the case of the anucleated merozoite, for example,\na functional activity unaccompanied by assimilation, yet identical\nwith the functional activity which is accompanied by assimilation in\nthe nucleated merozoite. The general movement, that of the cilia, the\ntaking of food, the evacuation of the f\u00e6ces, the contraction of the\npulsatile vacuoles, are the same. And this fact is the best proof that\nthis vital functional activity (with the organic destruction which is\nits energetic source) must be distinguished from the assimilation which\nusually follows it, and which in exceptional cases may not follow it.\n\nWe shall carry this discussion no farther. We have examined at some\nlength Le Dantec\u2019s views, and we have contrasted them with the doctrine\nwhich has been current in general physiology since the time of\nClaude Bernard, and this comparison does not turn out quite to their\nadvantage. It was inevitable that the experimental and realistic spirit\nwhich inspired the doctrine of the celebrated physiologist made his\nwork really too systematic. His formula, \u201clife is death,\u201d and the form\nhe gave his ideas, are not always irreproachably correct. They lend\nthemselves at times to criticism. Sometimes they require commentary.\nThese are errors of detail which Le Dantec has summarized somewhat\nroughly. There is no necessity to do this in his own case. We pay our\ntribute to the clearness of his language, although we believe the\nfoundations of his system are false and ill-founded. Their rigour is\npurely verbal. Their external qualities, their careful arrangement\nare well adapted to the seduction of the systematic mind prepared\nby mathematical teaching. This new theory of life is presented with\npedagogic talent of the highest order. We think we have shown that the\nfoundations are entirely fallacious, in particular the following:\u2014Vital\ncondition No. 2\u00ba; the confusion between functional activity and\nassimilating synthesis; the so-called absolute connection between\nmorphogeny and chemical composition; the fundamental distinction\nbetween elementary life and individual life.\n\n\n \u00a7 4. CHARACTERISTICS OF NUTRITION.\n\n\n_Definition of Nutrition._\u2014As we have just seen, the organism is the\nscene of chemical reactions of two kinds, the one destructive and\nsimplifying, the other synthetic, constructive, or assimilating. This\ntotality of reactions constitutes nutrition. Hence the two phases\nthat it is convenient to consider in this function\u2014_assimilation_ and\n_disassimilation_. This twofold chemical movement or _metabolism_\ncorresponding to the two categories of vital phenomena, of destruction\n(catabolism) and of synthesis (anabolism) is therefore the chemical\nsign of vitality in all its forms. But it is clear that disassimilation\nor organic destruction, which is destined to furnish energy to the\norganism for its different operations, reappears in the plan of the\ngeneral phenomena of nature. It is not specifically vital in its\nprinciple. Assimilation, on the other hand, is in this respect much\nmore characteristic.\n\nTo some physiologists nutrition is only assimilation. Of the two\naspects of metabolism they consider only one, the most typical,\n_Ad-similare_, to assimilate, to restore the substance borrowed\nfrom the ambient medium, the alimentary substances, _similar_ to\nliving matter, to make living matter of them, to increase active\nprotoplasm\u2014this is indeed the most striking phenomenon of vitality.\nTo grow, to increase, to expand, to invade, is the law of living\nmatter. Assimilation, nutrition in its essentials, is, according to\nthe definition of Ch. Robin, \u201cthe production by the living being of a\nsubstance identical with its own.\u201d It is the act by which the living\nmatter, the protoplasm of a given being, is created.\n\n_Permanence in Nutrition._\u2014Nutrition presents one quite remarkable\ncharacter\u2014permanence. It is a vital manifestation, a property if\nwe look at it in the cell, in the living substance, a function if\nwe consider it in the animal or in the plant as a whole, which is\nnever arrested. Its suspension involves _ipso facto_ the suspension\nof life itself. It is, in the words of Claude Bernard, that property\nof nutrition \u201cwhich, as long as it exists in an element, compels us\nto believe that this element is alive, and which, when it is absent,\ncompels us to believe that it is dead. It dominates all others by its\ngenerality and its importance. In a word, it is the absolute test of\nvitality.\u201d\n\n_Biological Energetics shows the Importance of Nutrition._\u2014We have\nindicated in advance the reason of its importance, showing that its two\nphases, disassimilation and assimilation, are the energetic condition\nof the two kinds of vital phenomena which we can distinguish.\n\nNutrition is a manufacture of protoplasm at the expense of the\nmaterials of the cellular ambient medium, which are assimilated\u2014_i.e._,\nmade chemically and physically similar to living matter and to the\nreserves it stores up. This operation, which is peculiarly chemical,\nis therefore indicated by the borrowing of materials from the external\nworld, a borrowing which is always going on, because the operation is\npermanent, and, let me add, because of the continual rejection of the\nwaste products of this manufacture. Our formula is:\u2014Nutrition is a\nchemistry which persists.\n\n_The Idea of the Vital Vortex is Erroneous._\u2014Here the effect has hidden\nthe cause from the eyes of the biologists. They have been struck by\nthe incessant entry and exit, by the never-ceasing passage, by the\n_cycle_ of matter through the living being without guessing its why\nand wherefore; and they have taken as a picture of the living being a\nvortex in which the essential form is maintained while the matter,\nwhich is accessory, flows on without a check. This is Cuvier\u2019s _vital\nvortex_. But for what purpose is this circulating matter used? They\nthought that it was employed entirely for the reconstitution of the\nliving substance, continually and inevitably destroyed by the vital\nMinotaur.\n\n_Destruction of Reserve-stuff_.\u2014Here again there is a mistake. Really\nliving substance is but little destroyed, and consequently requires\nvery little renewal by the functional activity of the animal machine.\nIts metabolism\u2014destruction and renewal\u2014is in every case infinitely less\nthan is supposed in the classical image of the vital vortex. It is\nthe merit of physiologists, and particularly of Pfl\u00fcger and Chauveau,\nto have worked for nearly forty years to establish this truth. They\nhave proved it, at least as far as the muscular tissue is concerned.\nProtoplasm, properly so-called, is only destroyed as the organs of a\nsteam engine are destroyed\u2014its tubes, its boiler, its furnace. And\nit matters little. We know that such an engine uses much coal, and\nwe know very little of its machinery and its metallic frame. And so\nit is with the cell, the living machine. A very small portion of the\nfood introduced will be assimilated in the living substance. By far\nthe greater part of it is destined to be worked up by the protoplasm\nand placed in reserve under the form of glycogen, albumen, and fat,\netc.\u2014_i.e._, compounds which are not the really living substance, the\nhereditary protoplasm, but the products of its industry, just as they\nare or may be the products of the industry of the chemist working in\nhis laboratory. They will be expended for the purpose of furnishing\nthe necessary energy to the vital functional activity, muscular\ncontraction, secretion, heat, etc., just as coal is expended to set\nthe steam engine going. The proof as far as the muscle is concerned\ndoes not stand alone. There are other examples. In particular,\nmicrographic physiologists who have studied nervous phenomena say\nthat the anatomical elements of the brain last indefinitely, and that\nthey continue as they are, without renewal from birth to death. The\npermanence of the consciousness, be it said in passing, is connected by\nthem with the permanence of the cerebral element (Marinesco).\n\nThus destruction is very restricted. There is only a very slight\ndisassimilation of the living matter, properly so-called, in the course\nof the vital functional activity. We may even go farther than this\nexperimental fact. This is what Le Dantec has done when he claims that\nthere is even an assimilation, an increase of the protoplasm. Strictly\nspeaking, this is possible, but there is no certain proof of it; and\nin any case we cannot agree with him when he affirms that the increase\nis the _direct result_ of the functional activity and blends with\nit in one single, unique operation. We must, on the contrary, agree\nwith Claude Bernard that it is only a _consequence_ of it, that it\nis produced in consequence of the existence of a bond of correlation\nbetween organic destruction and assimilating synthesis.\n\nWhy is there this bond? That is easily understood if we reflect that\nthe assimilating synthesis, an operation of endothermic, chemical\ncomplexity, naturally requires an exothermic counterpart, the organic\ndestruction which will set free this necessary energy.\n\n_Formative Assimilation of Reserve-stuff. Formative Assimilation of\nProtoplasm._\u2014It follows that there are in nutritive assimilation\nitself two distinct acts. The one consisting of the manufacture\nof reserve-stuff is the more obvious but the less specific; the\nother, really essential, is assimilation properly so-called, the\nreconstitution of the protoplasm. The former is indispensable to the\nproduction of the most prominent acts of vitality\u2014movement, secretion,\nproduction of heat. If it is suspended, functional activity is\narrested. We get _apparent death_, or _latent life_. But if the real\nassimilation is arrested, we have _real death_.\n\nAccording to this there would be a fundamental distinction between real\nand apparent death. The former would be characterized by an _arrest\nof the protoplasmic assimilation_ which is externally indicated by\nno sign. On the other hand, apparent death would be characterized\nby _the arrest of the formation and destruction of reserve-stuff_.\nIt would be externally manifested by two signs:\u2014The suppression of\nmaterial exchanges with the medium (respiration, alimentation) and the\nsuppression of the functional acts (production of movement, of heat, of\nelectricity, of glandular excretion).\n\nSuch would be the most expedient test for apparent or real death. The\nquestion occurs in the case of grains of corn in Egyptian tombs, and\nalso of hibernating animals and reviviscent beings, and, in general, in\nthe case of what has been called the state of _latent life_. But from\nthe practical point of view it is extremely difficult to apply this\ntest and to decide if the phenomena which are arrested in the grain\nat maturity, in Leeuwenhoek\u2019s tardigrada,[18] and in the dried-up\nAnguillulid\u00e6[19] of Baker and Spallanzani, in the encysted colpoda[20]\nthat a drop of warm water will revive, in the animals exposed by E.\nYung and Pictet to a cold of more than a 100\u00b0 C. below zero, are due\nto the general arrest of the two forms of assimilation, or to the\narrest of the manufacture and utilization of reserve-stuff alone, or\nfinally, to the arrest of protoplasmic assimilation alone. The latter,\nwhich is already very restricted in beings in a normal condition whose\ngrowth is terminated, may fall to the lowest degree in the being which,\nhaving no functional activity, is assimilating nothing. So that, to\ncut the question short, the experimenter who measures the value of\nthe exchanges between the being and the medium has seldom to do more\nthan decide between little and nothing. Hence his perplexity. But if\nexperiment hesitates, theory affirms: it admits _a priori_ that the\nmovement of protoplasmic assimilation, an essential sign of vitality,\nis neither checked nor renewed, but proceeds continuously.\n\n [18] Bear-animalcules, Sloth-animalcules. An order of Arachnida.\u2014TR.\n\n [19] Minute thread worms, known as paste-eels and vinegar-eels.\u2014TR.\n\n [20] Genus of Infusoria. Colpodea cucullus is found in infusions of\n hay.\u2014TR.\n\n\n_Is Nutrition, the Assimilating Synthesis, interrupted?_\u2014Nevertheless,\nthere are many reasons for suspending all judgment as to this\ninterpretation. It is questioned by most biologists. According to A.\nGautier, the preserved grain of corn and the dried up rotifera are not\nreally alive; they are like clocks in working order, ready to tell the\ntime, but awaiting in absolute repose the first vibration which will\nset them going. As for the grain, it is the air, heat, and moisture\nwhich supply the first impulse. In other words, the organization\nproper to the manifestation of life remains, but there is no life. The\nso-called arrested life is not a life.\n\nIt must be said, however, that the majority of physiologists refuse\nto accept this interpretation. They believe in an attenuation of the\nnutritive synthesis and not in its complete destruction. They think\nthat this total suppression would be contrary to current ideas relative\nto the perpetuity of the protoplasm and the limited duration of the\nliving element. The natural medium is variable, and even the mineral\ncannot remain eternally fixed. Still less is perennity a property of\nthe living being. If ordinary life is for each individual of limited\nduration, the arrested life must also be of limited duration. We cannot\nbelieve that after an indefinitely prolonged sleep the grain of corn,\nor the paste-eel, or the colpoda, emerging from their torpor can resume\ntheir existence, like the Sleeping Beauty, at the point at which it\nwas interrupted, and thus pass with a bound, as it were, through the\ncenturies.\n\nIn fact the maintenance of the vitality of grains of corn from the\nEgyptian tombs and their aptitude to germinate after thousands of\nyears are only fables or the result of imposture. Maspero, in a letter\naddressed to M. E. Griffon on the 15th July 1901, has clearly summed up\nthe situation by saying that the grains of corn bought from the fellahs\nalmost always germinate, but that this is never the case with those\nthat the experimenter himself takes from the tombs.\n\nTo sum up, we must use the same language of nutrition and of life,\nof their uninterrupted progress, of their continuity, of their\npermanence, of their activity, and of their slackening. Living\nmatter is always growing, much or little, slowly or quickly, in its\nreserve-stuff or in its protoplasm, for expenditure or accumulation.\nThis inevitability of growth defines it, characterizes it, and sums up\nits activity. Development and the evolution of growth are consequences\nor aspects of nutrition.\n\n\n\n\nBOOK IV.\n\nTHE LIFE OF MATTER.\n\n Summary: Chap. I. Universal life\u2014Opinions of philosophers and\n poets\u2014Continuity between brute and living bodies\u2014Origin of this\n principle.\u2014Chap. II. Origin of brute matter in living matter.\u2014Chap.\n III. Organization and chemical composition of brute and living\n bodies.\u2014Chap. IV. Evolution and transformation of brute and living\n bodies.\u2014Chap. V. Possession of a specific form\u2014Living bodies and\n crystals\u2014Cicatrization.\u2014Chap. VI. Nutrition in the living body\n and in the crystal.\u2014Chap. VII. Generation in brute and in living\n bodies\u2014Spontaneous generation.\n\n\n_Apparent Differences between Living and Brute Bodies. The Two\nKingdoms._\u2014It seems at first impossible that there should be any\nessential similarity between an inanimate object and a living being.\nWhat resemblance can be discovered between a stone, a lion, and an\noak? A comparison of the inert and immovable pebble with the leaping\nanimal, and with the plant extending its foliage gives an impression\nof vivid contrast. Between the organic and the inorganic worlds there\nseems to be an abyss. The first impressions we receive confirm this\nview; superficial investigation furnishes arguments for it. There is\nthus aroused in the mind of the child, and later in that of the man, a\nsharply marked distinction between the natural objects of the mineral\nkingdom on the one hand, and those of the two kingdoms of living beings\non the other.\n\nBut a more intimate knowledge daily tends to throw doubt upon the\nrigour or the absolute character of such a distinction. It shows that\nbrute matter can no longer be placed on one side and living beings on\nthe other. Scientists deliberately speak of \u201cthe life of matter,\u201d which\nseems to the average man a contradiction in terms. They discover in\ncertain classes of mineral bodies almost all the attributes of life.\nThey find in others fainter, but still recognizable indications of an\nundeniable relationship.\n\nWe propose to pass in review these analogies and resemblances, as has\nalready been done in a fairly complete manner by Leo Errera, C. E.\nGuillaume, L. Bourdeau, Ed. Griffon, and others. We will consider the\nfine researches of Rauber, of Ostwald, and of Tammann upon crystals\nand crystalline germs\u2014researches which are merely a continuation of\nthose of Pasteur and of Gernez. These show that crystalline bodies\nare endowed with the principal attributes of living beings\u2014_i.e._,\na rigorously defined form; an aptitude for acquiring it, and for\nre-establishing it by repairing any mutilations that may be inflicted\nupon it; nutritive growth at the expense of the mother liquor which\nconstitutes its culture medium; and, finally\u2014a still more incredible\nproperty\u2014all the characteristics of reproduction by generation. Other\ncurious facts observed by skilful physicists\u2014W. Roberts-Austen, W.\nSpring, Stead, Osmond, Guillemin, Charpy, C. E. Guillaume\u2014show that\nthe immutability even of bodies supposed to be the most rigid of all,\nsuch as glass, the metals, steel, and brass, is apparent rather than\nreal. Beneath the surface of the metal that seems to us inert there\nis a swarming population of molecules, displacing each other, moving\nabout, and arranging themselves so as to form definite figures, and\nassuming forms adapted to the conditions of the environment. Sometimes\nit is years before they arrive at the state of ultimate and final\nequilibrium\u2014which is that of eternal rest.\n\nHowever, in order to understand these facts and their interpretations,\nit is necessary to pass in review the fundamental characteristics of\nliving beings. It will be shown that these very characteristics are\nfound in inanimate matter.\n\n\n\n\n CHAPTER I.\n\n UNIVERSAL LIFE. OPINIONS OF PHILOSOPHERS AND POETS.\n\n \u00a7 1. Primitive beliefs; the ideas of poets.\u2014\u00a7 2. Opinions of\n philosophers\u2014Transition from brute to living bodies\u2014The principle of\n continuity: continuity by transition: continuity by summation\u2014Ideas of\n philosophers as to sensibility and consciousness in brute bodies\u2014The\n general principle of homogeneity\u2014The principle of continuity as a\n consequence of the principle of homogeneity.\n\n\n \u00a7 1. PRIMITIVE BELIEFS. IDEAS OF THE POETS.\n\n\nThe teaching of science as to the analogies between brute bodies and\nliving bodies accords with the conceptions of the philosophers and\nthe fancies of the poets. The ancients held that all bodies in nature\nwere the constituent parts of a universal organism, the macrocosm,\nwhich they compared to the human microcosm. They attributed to it a\nprinciple of action, the _psyche_, analogous to the vital principle,\nand this psyche directed phenomena; and also an intelligent principle,\nthe _nous_, analogous to the soul, and the _nous_ served for the\ncomprehension of phenomena. This universal life and this universal soul\nplayed an important part in their metaphysical systems.\n\nIt was the same with the poets. Their tendency has always been to\nattribute life to Nature, so as to bring her into harmony with our\nthoughts and feelings. They seek to discover the life or soul hidden in\nthe background of things.\n\n \u201cHark to the voices. Nothing is silent.\n\n Winds, waves, and flames, trees, reeds, and rocks\n All live; all are instinct with soul.\u201d\n\nAfter making proper allowance for emotional exaggeration, ought we\nto consider these ideas as the prophetic divination of a truth which\nscience is only just beginning to dimly perceive? By no means. As\nRenan has said, this universal animism, instead of being a product\nof refined reflection, is merely a legacy from the most primitive of\nmental processes, a residue of conceptions belonging to the childhood\nof humanity. It recalls the time when men conceived of external things\nonly in terms of themselves; when they pictured each object of nature\nas a living being. Thus, they personified the sky, the earth, the sea,\nthe mountains, the rivers, the fountains, and the fields. They likened\nto animate voices the murmur of the forest:\u2014\n\n \u201c ... The oak chides and the birch\n Is whispering....\n And the beech murmurs....\n The willow\u2019s shiver, soft and faint, sounds like a word.\n The pine-tree utters mysterious moans.\u201d\n\nFor primitive man, as for the poet of all times, everything is alive,\nand every sound is due to a being with feelings similar to our own.\nThe sighing of the breeze, the moan of the wave upon the shore, the\nbabbling of the brook, the roaring of the sea, and the pealing of the\nthunder are nothing less than sad, joyous, or angry living voices.\n\nThese impressions were embodied in ancient mythology, the graceful\nbeauty of which does not conceal its inadequacy. Then they passed\ninto philosophy and approached the realm of science. Thales believed\nthat all bodies in nature were animate and living. Origen considered\nthe stars as actual beings. Even Kepler himself attributed to the\ncelestial bodies an internal principle of action, which, it may be\nsaid in passing, is contrary to the law of the inertia of matter,\nwhich has been wrongly ascribed to him instead of to Galileo. The\nterrestrial globe was, according to him, a huge animal, sensitive to\nastral influences, frightened at the approach of the other planets, and\nmanifesting its terror by tempests, hurricanes, and earthquakes. The\nwonderful flux and reflux of the ocean was its breathing. The earth had\nits blood, its perspiration, its excretions; it also had its foods,\namong which was the sea water which it absorbs by numerous channels.\nIt is only fair to add that at the end of his life Kepler retracted\nthese vague dreams, ascribing them to the influence of J. C. Scaliger.\nHe explained that by the soul of the celestial bodies he meant nothing\nmore than their motive force.\n\n\n \u00a7 2. OPINION OF THE PHILOSOPHERS.\n\n\n_Transition from Brute to Living Bodies._\u2014The lowering of the barrier\nbetween brute bodies and living bodies began with those philosophers\nwho introduced into the world the great principles of continuity and\nevolution.\n\n_The Principle of Continuity._\u2014First and foremost we must mention\nLeibniz. According to the teaching of that illustrious philosopher,\nas interpreted by M. Fouill\u00e9e, \u201cthere is no inorganic kingdom, only\na great organic kingdom, of which mineral, vegetable, and animal\nforms are the various developments.... Continuity exists everywhere\nthroughout the world; everywhere is life and organization. Nothing is\ndead; life is universal.\u201d It follows that there is no interruption\nor break in the succession of natural phenomena; that everything is\ngradually developed; and finally, that the origin of the organic being\nmust be sought in the inorganic. Life, properly so called, has not,\nin fact, always existed on the surface of the globe. It appeared at a\ncertain geological epoch, in a purely inorganic medium, by reason of\nfavourable conditions. The doctrine of continuity compels us, however,\nto admit that it pre-existed on the globe under some rudimentary form.\n\nThe modern philosophers who are imbued with these principles, MM.\nFouill\u00e9e, L. Bourdeau, and A. Sabatier, express themselves in similar\nlanguage. \u201cDead matter and living matter are not two absolutely\ndifferent entities, but represent two forms of the same matter,\ndiffering only in degree, sometimes but slightly.\u201d When it is only\na matter of degree, it cannot be held that these views are opposed.\nInequalities must not be interpreted as contrary attributes, as when\nthe untrained mind considers heat and cold as objective states,\nqualitatively opposed to each other.\n\n_Continuity by Transition._\u2014The argument which leads us to remove the\nbarrier between the two kingdoms, and to consider minerals as endowed\nwith a sort of rudimentary life, is the same as that which compels\nus to admit that there is no fundamental difference between natural\nphenomena. There are transitions between what lives and what does not,\nbetween the animate being and the brute body. And in the same way there\nare transitions between what thinks and what does not think, between\nwhat is thought and what is not thought, between the conscious and\nthe unconscious. This idea of insensible transition, of a continuous\npath between apparent antitheses, at first arouses an insuperable\nopposition in minds not prepared for it by a long comparison of facts.\nIt is slowly realized, and finally is accepted by those who, in the\nworld of things, follow the infinity of gradations presented by natural\nphenomena. The principle of continuity comes at last to constitute,\nas one may say, a mental habit. Thus the man of science may be led,\nlike the philosopher, to entertain the idea of a rudimentary form of\nlife animating matter. He may, like the philosopher, be guided by\nthis idea; he may attribute _a priori_ to brute matter all the really\nessential qualities of living beings. But this must be on the condition\nthat, assuming these properties to be common, he must afterwards\ndemonstrate them by means of observation and experiment. He must show\nthat molecules and atoms, far from being inert and dead masses, are in\nreality active elements, endowed with a kind of inferior life, which\nis manifested by all the transformations observed in brute matter,\nby attractions and repulsions, by movements in response to external\nstimuli, by variations of state and of equilibrium; and finally, by the\nsystematic methods according to which these elements group themselves,\nconforming to those definite types of structure by means of which they\nproduce different species of chemical compounds.\n\n_Continuity by Summation._\u2014The idea of summation leads by another path\nto the same result. It is another form of the principle of continuity.\nA sum total of effects, obscure and indistinct in themselves, produces\na phenomenon appreciable, perceptible, and distinct, apparently,\nbut not really, heterogeneous in its components. The manifestations\nof atomic or molecular activity thus become manifestations of vital\nactivity.\n\nThis is another consequence of the teaching of Leibniz. For, according\nto his philosophical theory, individual consciousness, like individual\nlife, is the collective expression of a multitude of elementary lives\nor consciousnesses. These elements are inappreciable because of their\nlow degree, and the real phenomenon is found in the sum, or rather\nthe _integral_, of all these insensible effects. The elementary\nconsciousnesses are harmonized, unified, integrated into a result that\nbecomes manifest, just as \u201cthe sounds of the waves, not one of which\nwould be heard if by itself, yet, when united together and perceived at\nthe same instant, become the resounding voice of the ocean.\u201d\n\n_Ideas of the Philosophers as to Sensibility and Consciousness in\nBrute Bodies._\u2014The philosophers have gone still further in the way\nof analogies, and have recognized in the play of the forces of brute\nmatter, particularly in the play of chemical forces, a mere rudiment\nof the appetitions and tendencies that regulate, as they believe, the\nfunctional activity of living beings\u2014a trace, as it were, of their\nsensibility. To them reactions of matter indicate the existence of a\nkind of _hedonic consciousness_\u2014_i.e._, a consciousness reduced simply\nto a distinction between comfort and discomfort, a desire for good and\nrepulsion from evil, which they suppose to be the universal principle\nof all activity. This was the view held by Empedocles in antiquity;\nit was that of Diderot, of Cabanis, and, in general, of the modern\nmaterialistic school, eager to find, even in the lowest representatives\nof the inorganic world, the first traces of the vitality and\nintellectual life which blossom out at the top of the scale in the\nliving world.\n\nSimilar ideas are clearly seen in the early history of all natural\nsciences. It was this same principle of appetition, or of love and of\nrepulsion or hate that, under the names of affinity, selection, and\nincompatibility, was thought to direct the transformations of bodies\nwhen chemistry first began; when Boerhaave, for example, compared\nchemical combinations to voluntary and conscious alliances, in which\nthe respective elements, drawn together by sympathy, contracted\nappropriate marriages.\n\n_General Principle of the Homogeneity of the Complex and its\nComponents._\u2014The assimilation of brute bodies to living bodies, and\nof the inorganic kingdom to the organic, was, in the mind of these\nphilosophers, the natural consequence of positing _a priori_ the\nprinciples of continuity and evolution. There is, however, a principle\nunderlying these principles. This principle is not expressed explicitly\nby the philosophers; it is not formulated in precise terms, but is more\nor less unconsciously implied; it is everywhere applied. It, however,\nmay be clearly seen behind the apparatus of philosophical argument It\nis the assertion that no arrangement or combination of elements can\nput forth any new activity essentially different from the activities\nof the elements of which it is composed. Man is living clay, say\nDiderot and Cabanis; and, on the other hand, he is a thinking being.\n_As it is impossible to produce that which thinks from that which\ndoes not think_, the clay must possess a rudiment of thought. But is\nthere not another alternative? May not the new phenomenon, thought,\nbe the effect of the arrangement of this clay? If we exclude this\nalternative, we must then consider arrangement and organization as\nincapable of producing in arranged and organized matter a new property\ndifferent from that which it presented before such arrangement. Living\nprotoplasm, says another, is merely an assemblage of brute elements;\n\u201cthese brute elements must therefore possess a rudiment of life.\u201d This\nis the same implied supposition which we have just considered; if life\nis not the basis of each element, it cannot result from their simple\nassemblage.\n\nMan and animals are combinations of atoms, says M. le Dantec. It is\nmore natural to admit that human consciousness is the result of the\nelementary consciousness of the constituent atoms than to consider\nit as resulting from construction by means of elements with no\nconsciousness. \u201cLife,\u201d says Haeckel, \u201cis universal; we could not\nconceive of its existence in certain aggregates of matter if it did not\nbelong to their constituent elements.\u201d Here the postulate is almost\nexpressed.\n\nThe argument is always the same; even the same words are used:\nthe fundamental hypothesis is the same; only it remains more or\nless unexpressed, more or less unperceived. It may be stated as\nfollows:\u2014Arrangement, assemblage, construction, and aggregation are\npowerless to bring to light in the complex anything new and essentially\nheterogeneous to what already exists in the elements. Reciprocally,\ngrouping reveals in a complex a property and character which is the\ngradual development of an analogous property and character in the\nelements. It is in this sense that there exists a collective soul in\ncrowds, the psychology of which has been discussed by M. G. Le Bon. In\nthe same way, many sociologists, adopting the views advanced by P. de\nLilienfeld in 1865, attribute to nations a formal individuality, after\nthe type of that possessed by each of their constituent members. M.\nIzolet considers society as an organism, which he calls a \u201chyperzoan.\u201d\nHerbert Spencer has developed the comparison of the collective organism\nwith the individual organism, insisting on their resemblances and\ndifferences. Th. Ribot has dwelt, in particular, on the resemblances.\n\nThe postulate that we have clearly stated here is accepted by many as\nan axiom. But it is not an axiom. When we say that there is nothing\nin the complex that cannot be found in the parts, we think we are\nexpressing a self-evident truth; but we are, in fact, merely stating\nan hypothesis. It is assumed that arrangement, aggregation, and\ncomplicated and skilful grouping of elements can produce nothing really\nnew in the order of phenomena. And this is an assertion that requires\nverification in each particular case.\n\n_The Principle of Continuity, a Consequence of the Preceding._\u2014Let us\napply this principle to the beings in nature. All beings in nature are,\naccording to current ideas, arrangements, aggregates, or groupings of\nthe same universal matter, that is to say, of the same simple chemical\nbodies. It results from the preceding postulate that their activities\ncan only differ in degree and form, and not fundamentally. There is\nno essential difference of nature between the activities of various\ncategories of beings, no heterogeneity, no discontinuity. We may pass\nfrom one to another without coming to an hiatus or impassable gulf.\nThe law of continuity thus appears as a simple consequence of the\nfundamental postulate. And so it is with the law of evolution, for\nevolution is merely continuity of action.\n\nSuch are the origins of the philosophical doctrine which universalizes\nlife and extends it to all bodies in nature.\n\nIt may be remarked that this doctrine is not confined to any particular\nschool or sect. Leibniz was by no means a materialist, and he endowed\nhis mundane elements, his _monads_, not only with a sort of life, but\neven with a sort of soul. Father Boscovitch, Jesuit as he was, and\nprofessor in the college of Rome, did not deny to his _indivisible\npoints_ a kind of inferior vitality. St. Thomas, too, the angelical\ndoctor, attributed, according to M. Gardair, to inanimate substances a\ncertain kind of activity, inborn inclinations, and a real appetition\ntowards certain acts.\n\n\n\n\nCHAPTER II.\n\nORIGIN OF BRUTE MATTER IN LIVING MATTER.\n\n Spontaneous generation: an episode in the history of the\n globe\u2014Verification of the identity between brute and living\n matter\u2014Slow identification\u2014Rapid identification\u2014Contrary\n opinion\u2014Hypothesis of cosmozoa; cosmic panspermia\u2014Hypothesis of\n pyrozoa.\n\n\nThere should be two ways of testing the doctrine of the essential\nidentity of brute and living matter\u2014one slow and more laborious, the\nother more rapid and decisive.\n\n_Identification of the Two Matters, Brute and Living._\u2014The laborious\nmethod, which we will be obliged to follow, consists in the attentive\nexamination of the various activities by which life is manifested, and\nin finding more or less crude equivalents for them in all brute beings,\nor in certain of them.\n\n_Rapid Verification. Spontaneous Generation._\u2014The rapid and decisive\nmethod, which, unhappily, is beyond our resources, would consist in\nshowing unquestionable, clearly marked life, the superior life, arising\nfrom the kind of inferior life that is attributed to matter in general.\nIt would be necessary completely to construct in all its parts, by a\nsuitable combination of inorganic materials, a single living being,\neven the humblest plant or the most rudimentary animal. This would\nindeed be an irrefutable proof that the germs of all vital activity are\ncontained in the molecular activity of brute bodies, and that there is\nnothing essential to the latter that is not found in the former.\n\nUnhappily this demonstration cannot be given. Science furnishes no\nexample of it, and we are forced to have recourse to the slow method.\n\nThe question here involved is that of spontaneous generation. It is\nwell known that the ancients believed in spontaneous generation,\neven for animals high in the scale of organization. According to Van\nHelmont, mice could be born by some incomprehensible fermentation in\ndirty linen mixed with wheat. Diodorus speaks of animal forms which\nwere seen to emerge, partly developed, from the mud of the Nile.\nAristotle believed in the spontaneous birth of certain fishes. This\nbelief, though rejected as to the higher forms, was for a long time\nheld with regard to the lower forms of animals, and to insects\u2014such as\nthe bees which the shepherd of Virgil saw coming out from the flanks\nof the dead bullock\u2014flies engendered in putrefying meat, fruit worms\nand intestinal worms; finally, with regard to infusoria and the most\nrudimentary vegetables. The hypothesis of the spontaneous generation of\nthe living being at the expense of the materials of the ambient medium\nhas been successively driven from one classificatory group to another.\nThe history of the sciences of observation is also a history of the\nconfutation of this theory. Pasteur gave it the finishing stroke, when\nhe showed that the simplest microorganisms obeyed the general law which\ndeclares that the living being is formed only by _filiation_\u2014that is\nto say, by the intervention of a pre-existing living organism.\n\n_Spontaneous Generation an Episode in the History of the Globe._\u2014Though\nwe have been unable to effect spontaneous generation up to the present,\nit has been referred by Haeckel to a more or less distant past, to\nthe time when the cooling of the globe, the solidification of its\ncrust, and the condensation of aqueous vapour upon its surface created\nconditions compatible with the existence of living beings similar\nto those with which we are acquainted. Lord Kelvin has fixed these\ngeological events as occurring from twenty to forty million years ago.\nThen circumstances became propitious for the appearance of the first\norganisms, whence were successively derived those which now people the\nearth and the waters.\n\nCircumstances favourable to the appearance of the first beings\napparently occurred only in a far distant past; but most physiologists\nadmit that if we knew exactly these circumstances, and could reproduce\nthem, we might also expect to produce their effect\u2014namely, the creation\nof a living being, formed in all its parts, developed from the\ninorganic kingdom. To all those who held this view the impotence of\nexperiment at the present time is purely temporary. It is comparable to\nthat of primitive men before the time of Prometheus; they, not knowing\nhow to produce fire, could only get it by transmitting it from one to\nanother. It is due to the inadequacy of our knowledge and the weakness\nof our means; it does not contradict the possibility of the fact.\n\n_Contrary Opinion. Life did not Originate on our Globe._\u2014But all\nbiologists do not share this opinion. Some, and not the least eminent,\nhold it to be an established fact that it is impossible for life to\narise from a concurrence of inorganic materials and forces. This was\nthe opinion of Ferdinand Cohn, the great botanist; of H. Richter, the\nSaxon physician, and of W. Preyer, a physiologist well known from his\nremarkable researches in biological chemistry. According to these\nscientists, life on the surface of the globe cannot have appeared as a\nresult of the reactions of brute matter and the forces that continue to\ncontrol it.\n\nAccording to F. Cohn and PI. Richter, life had no beginning on our\nplanet. It was transported to the earth from another world, from the\ncosmic medium, under the form of cosmic germs, or _cosmozoa_, more\nor less comparable to the living cells with which we are acquainted.\nThey may have made the journey either enclosed in meteorites, or\nfloating in space in the form of cosmic dust. The theory in question\nhas been presented in two forms:\u2014_The Hypothesis of Meteoric Cosmozoa_,\nby a French writer, the Count de Salles-Guyon; and that of _cosmic\npanspermia_ brought forward in 1865 and 1872 by F. Cohn and H. Richter.\n\n_Hypothesis of the Cosmozoa._\u2014The hypothesis of the cosmozoa, living\nparticles, protoplasmic germs emanating from other worlds and reaching\nthe earth by means of aerolites, is not so destitute of probability\nas one might at first suppose. Lord Kelvin and Helmholtz gave it the\nsupport of their high authority. Spectrum analysis shows in cometary\nnebul\u00e6 the four or five lines characteristic of hydro-carbons. Cosmic\nmatter, therefore, contains compounds of carbon, substances that are\nespecially typical of organic chemistry. Besides, carbon and a sort\nof humus have been found in several meteorites. To the objection\nthat these aerolites are heated while passing through our atmosphere,\nHelmholtz replies that this elevation of temperature may be quite\nsuperficial and may allow micro-organisms to subsist in their interior.\nBut other objections retain their force:\u2014First, that of M. Verworn, who\nconsiders the hypothesis of cosmic germs as inconsistent with the laws\nof evolution; and that of L. Errera, who denies that the conditions\nnecessary for life exist in interplanetary bodies.\n\n_Hypothesis of Cosmic Panspermia._\u2014Du Bois-Reymond has given the name\nof _cosmic panspermia_ to a theory very similar to the preceding,\nformulated by F. Cohn in 1872. The first living germs arrived on our\nglobe mingled with the cosmic dust that floats in space and falls\nslowly to the surface of the earth. L. Errera observes that if they\nescape by this gentle fall the dangerous heating of meteorites, they\nstill remain exposed to the action of the photic rays, which is\ngenerally destructive to germs.\n\n_Hypothesis of Pyrozoa._\u2014W. Preyer declined to accept this cosmic\ntransmigration of the simplest living beings, nor would he allow\nthe intervention of other worlds into the history of our own. Life,\naccording to him, must have existed from all time, even when the globe\nwas an incandescent mass. But it was not the same life as at present.\nVitality must have undergone many profound changes in the course of\nages. The _pyrozoa_, the first living beings, vulcanians, were very\ndifferent from the beings of the present day that are destroyed by\na slight elevation of temperature. No doubt this theory of pyrozoa,\nproposed by W. Preyer in 1872, seems quite chimerical, and akin\nto Kepler\u2019s dreamy visions. But in a certain way it accords with\ncontemporary ideas concerning the life of _matter_. It is related\nto them by the evolution which it implies in the materials of the\nterrestrial globe.\n\nAccording to Preyer, primitive life existed in fire. Being igneous\nmasses in fusion, the pyrozoa lived after their own manner; their\nvitality, slowly modified, assumed the form which it presents to-day.\nYet, in this profound transformation their number has not varied, and\nthe total quantity of life in the universe has remained unchanged.\n\nHere we recognize the ideas of Buffon. These cosmozoa, these pyrozoa,\nhave a singular resemblance to the _organic molecules_ of \u201clive matter\u201d\nof the illustrious naturalist\u2014distributed everywhere, indestructible,\nand forming living structures by their concentration.\n\nBut we must leave these scientific or philosophical theories, and come\nto arguments based upon facts.\n\nIt is in a spirit quite different from that of the poets, the\nmetaphysicians, and the more or less philosophical scientists that\nthe science of our days looks at the more or less obscure vitality of\ninanimate bodies. It claims that we may recognize in them, in a more or\nless rudimentary state, the action of the factors which intervene in\nthe case of living beings, the manifestation of the same fundamental\nproperties.\n\n\n\n\nCHAPTER III.\n\nORGANIZATION AND CHEMICAL COMPOSITION OF LIVING AND BRUTE MATTER.\n\n Laws of the organization and of the chemical composition of living\n beings\u2014Relative value of these laws; vital phenomena in crushed\n protoplasm\u2014Vital phenomena in brute bodies.\n\n\n_Enumeration of the Principal Characters of Living Beings._\u2014The\nprogramme which we have just sketched compels us to look in the brute\nbeing for the properties of living beings. What, then, are, in fact,\nthe characteristics of an authentic, complete, living being? What are\nits fundamental properties? We have enumerated them above as follows:\u2014A\ncertain chemical composition, which is that of living matter; a\nstructure or organization; a specific form; an evolution which has a\nduration, that of life, and an end, death; a property of growth or\nnutrition; a property of reproduction. Which of these characters counts\nfor most in the definition of life? Are they all equally necessary? If\nsome of them were wanting, would that justify the transference of a\nbeing, who might possess the rest, from the animate world to that of\nminerals? This is precisely the question that is under consideration.\n\n_Organization and Chemical Composition of Living Beings._\u2014All that we\nknow concerning the constitution of living matter and its organization\nis summed up in the laws of the _chemical unity_ and the _morphological\nunity of living beings_ (v. Book III.). These laws seem to be a\nlegitimate generalization from all the facts observed. The first\nstates that the phenomena of life are manifested only in and through\nliving matter, protoplasm\u2014_i.e._, in and through a substance which\nhas a certain chemical and physical composition. Chemically it is a\nproteid complexus with a hexonic nucleus. Physically it shows a frothy\nstructure analogous to that resulting from the mixture of two granular,\nimmiscible liquids, of different viscosities. The second law states\nthat the phenomena of life can only be maintained in a protoplasm which\nhas the organization of the complete cell, with its cellular body and\nnucleus.\n\n_Relative Value of these Laws. Exceptions._\u2014What is the signification\nof these laws of the chemical composition and organization of living\nbeings? Evidently that life in all its plenitude can only exist and be\nperpetuated under their protection. If these laws were absolute, if\nit were true that no life were possible but in and through albuminous\nprotoplasm, but in and through the cell, the problem of \u201cthe life of\nmatter\u201d would be decided in the negative.\n\nMay it not happen, however, that fragmentary and incomplete vital\nmanifestations, progressive traces of a true life, may occur under\ndifferent conditions; for example, in matter which is not protoplasm,\nand in a body which has a structure differing from that of a cell\u2014that\nis to say, in a being which would be neither animal nor plant? We must\nseek the answer to this question by an appeal to experiment.\n\nWithout leaving the animal and vegetable kingdoms\u2014_i.e._, real living\nbeings\u2014we already see less rigour in the laws governing chemical\nconstitution and cellular organization.\n\nExperiments in merotomy\u2014_i.e._, in amputation\u2014carried out on the\nnervous element by Waller, on infusoria by Brandt, Gruber, Balbiani,\nNussbaum, and Verworn, show us the necessity of the presence of the\ncellular body and the nucleus\u2014_i.e._, of the integrity of the cell. But\nthey also teach us that when that integrity no longer exists death does\nnot immediately follow. A part of the vital functions continues to be\nperformed in denucleated protoplasm, in a cell which is mutilated and\nincomplete.\n\n_Vital Phenomena in Crushed Protoplasm._\u2014It is true also that grinding\nand crushing suppress the greater part of the functions of the cell.\nBut tests with pulps of various organs and with those of certain\nyeasts also show that protoplasm, even though ground and disorganized,\ncannot be considered as inert, and that it still exhibits many of its\ncharacteristic phenomena; for example, the production of diastases,\nthe specific agents of vital chemistry. Finally, while we do not\nknow enough about the actions of which the secondary elements of\nprotoplasm\u2014its granulations, its filaments\u2014are capable, which this or\nthat method of destruction may bring to light, at least we know that\nactions of this kind exist.\n\nTo sum up, we are far from being able to deny that rudimentary,\nisolated vital acts may be produced by the various bodies that result\nfrom the dismemberment of protoplasm. The integrity of the cellular\norganization, even the integrity of protoplasm itself, are therefore\nnot indispensable for these partial manifestations of vitality.\n\nBesides, biologists admit that there exist within the protoplasm\naliquot parts, elements of an inferior order, which possess special\nactivities. These secondary elements must have the principle of their\nactivity within themselves. Such are the _biophors_ to which Weismann\nattributes the vital functions of the cell, nutrition, growth, and\nmultiplication. If there are biophors within the cell, we may imagine\nthem outside the cell, and since they carry within themselves the\nprinciple of their activity they may exercise it in an independent\nmanner. Unhappily the biophors, and other constituent elements of\nthat kind, are purely hypothetical. They are like Darwin\u2019s gemmules,\nAltmann\u2019s bioblasts, and the pangens of De Vries. They have no relation\nto facts of observation and to real existence.\n\n_Vital Phenomena in Brute Bodies._\u2014There is no doubt that certain\nphenomena of vitality may occur outside of the cellular atmosphere.\nAnd carrying this further, we may admit that they may be produced in\ncertain slightly organized bodies (crushed cells), and then in certain\nunorganized bodies in certain brute beings. In every case it is certain\nthat effects are produced at any rate similar to those which are\ncharacteristic of living matter. It is for observation and experiment\nto decide as to the degree of similarity, and their verdict is that the\nsimilarity is complete. The crystals and the crystalline germs studied\nby Ostwald and Tammann are the seat of phenomena which are quite\ncomparable to those of vitality.\n\n\n\n\n CHAPTER IV.\n\n EVOLUTION AND MUTABILITY OF LIVING MATTER AND BRUTE MATTER.\n\n Supposed immobility of brute bodies\u2014Mobility and mutability of the\n sidereal world.\u2014\u00a7 1. The movement of particles and molecules in brute\n bodies\u2014The internal movements of brute bodies\u2014Kinetic conception of\n molecular motion\u2014Reality of the motion of particles\u2014Comparison of the\n activity of particles with vital activity.\u2014\u00a7 2. Brownian movement\u2014Its\n existence\u2014Its character\u2014Its independence of the nature of the bodies\n and of the nature of the environment\u2014Its indefinite duration\u2014Its\n independence of external conditions\u2014The Brownian movement must be the\n first stage of molecular motion.\u2014\u00a7 3. Motion of particles\u2014Migration of\n material particles\u2014Migration under the action of weight; of diffusion;\n of electrolysis; of mechanical pressure.\u2014\u00a7 4. Internal activity of\n alloys\u2014Their structure\u2014Changes produced by deforming agencies\u2014Slow\n return to equilibrium\u2014Residual effect\u2014Effect of annealing; effect of\n stretching\u2014Nickel steel\u2014Colour photography\u2014Conclusion\u2014Relations of the\n environment to the living or brute matter.\n\n\nOne of the most remarkable characteristics of a living being is its\nevolution. It undergoes a continuous change. It starts from something\nvery small; it assumes a configuration and grows; in most cases\nit declines and disappears, having followed a course which may be\npredicted\u2014a sort of ideal trajectory.\n\n_Supposed Immobility of Brute Bodies._\u2014It may be asked whether this\nevolution, this directed mobility, is so exclusively a feature of the\nliving being as it appears, and if many brute bodies do not present\nsomething analogous to it. We may answer in no uncertain tones.\n\nBichat was wrong when he contrasted in this respect brute bodies with\nliving bodies. Vital properties, he said, are temporary; it is their\nnature to be exhausted; in time they are used up in the same body.\nPhysical properties, on the contrary, are eternal. Brute bodies have\nneither a beginning nor an inevitable end, neither age, nor evolution;\nthey remain as immutable as death, of which they are the image.\n\n_Mobility and Mutability of the Sidereal World._\u2014This is not true,\nin the first place, of the sidereal bodies. The ancients held the\nsidereal world to be immutable and incorruptible. The doctrine of\nthe incorruptibility of the heavens prevailed up to the seventeenth\ncentury. The observers who at that epoch directed towards the heavens\nthe first telescope, which Galileo had just invented, were struck with\nastonishment at discovering a change in that celestial firmament which\nthey had hitherto believed incorruptible, and at perceiving a new star\nthat appeared in the constellation Ophiuchus. Such changes no longer\nsurprise us. The cosmogonic system of Laplace has become familiar to\nall cultivated minds, and every one is accustomed to the idea of the\ncontinual mobility and evolution of the celestial world. \u201cThe stars\nhave not always existed,\u201d writes M. Faye; \u201cthey have had a period of\nformation; they will likewise have a period of decline, followed by\nfinal extinction.\u201d\n\nThus all the bodies of inanimate nature are not eternal and immutable;\nthe celestial bodies are eminently susceptible of evolution, slow\nindeed with that we observe on the surface of our globe; but this\ndisproportion, corresponding to the immensity of time and of cosmic\nspaces as compared with terrestrial measurements, should not mislead us\nas to the fundamental analogy of the phenomena.\n\n\n \u00a7 1. THE MOVEMENT OF PARTICLES AND MOLECULES IN BRUTE BODIES.\n\n\nIt is not only in celestial spaces that we must search for that\nmobility of brute matter which imitates the mobility of living matter.\nIn order to find it we have only to look about us, or to inquire from\nphysicists and chemists.\n\nAs far as geologists are concerned, M. le Dantec tells us somewhere of\none who divided minerals into _living rocks_\u2014rocks capable of change\nof structure, of evolution under the influence of atmospheric causes;\nand _dead rocks_\u2014rocks which, like clay, have found at the end of all\ntheir changes a final state of repose. Jerome Cardan, a celebrated\nscientist of the sixteenth century, at once mathematician, naturalist,\nand physician, declared not only that stones live, but that they suffer\nfrom disease, grow old, and die. The jewellers of the present day use\nsimilar language of certain precious stones; the torquoise, for example.\n\nThe alchemists carried these ideas to an extreme. It is not necessary\nhere to recall the past, to evoke the hermetic beliefs and the dreams\nof the alchemists, who held that the different kinds of matter lived,\ndeveloped, and were transmuted into each other.\n\nI refer to precise and recent data, established by the most expert\ninvestigators, and related by one of them, Charles Edward Guillaume,\nsome years ago, before the _Soci\u00e9t\u00e9 helv\u00e9tique des Sciences\nnaturelles_. These data show that determinate forms of matter may\nlive and die, in the sense that they may be slowly and continuously\nmodified, always in the same direction, until they have attained an\nultimate and definitive state of eternal repose.\n\n_The Internal Movements of Bodies._\u2014Swift\u2019s reply to an idle fellow who\nspoke slightingly of work is well known. \u201cIn England,\u201d said the author\nof _Gulliver\u2019s Travels_, \u201cmen work, women work, horses work, oxen work,\nwater works, fire works, and beer works; it is only the pig who does\nnothing at all; he must, therefore, be the only gentleman in England.\u201d\nWe know very well that English gentlemen also work. Indeed, everybody\nand everything works. And the great wit was nearer right than he\nsupposed in comparing men and things in this respect. Everything is at\nwork; everything in nature strives and toils, at every stage, in every\ndegree. Immobility and repose in the case of natural things are usually\ndeceptive; the seeming quietude of matter is caused by our inability\nto appreciate its internal movements. Because of their minuteness we\ndo not perceive the swarming particles that compose it, and which,\nunder the impassible surface of the bodies, oscillate, displace each\nother, move to and fro, and group themselves into forms and positions\nadapted to the conditions of the environment. In comparison with these\nmicroscopic elements we are like Swift\u2019s giant among the Lilliputians;\nand this is far from being a sufficiently forcible comparison.\n\n_Kinetic Conception of Molecular Motion._\u2014The idea of this peculiar\nform of motion is by no means new to us. We were familiarized with\nit in scientific theories during our school days. The atomic theory\nteaches us that matter behaves, from a chemical point of view, as if it\nwere divided into molecules and atoms. The kinetic theory explains the\nconstitution of gases and the effects of heat by supposing that these\nparticles are endowed with movements of rotation and displacement.\nThe wave theory explains photic phenomena by supposing peculiar\nvibratory movements in a special medium\u2014the ether. But these are merely\nhypotheses which are not at all necessary; they are the images of\nthings, not the things themselves.\n\n_Reality of the Motion of Particles._\u2014Here there is no question of\nhypotheses. This internal agitation, this interior labour, this\nincessant activity of matter are positive facts, an objective reality.\nIt is true that when the chemical or mechanical equilibrium of bodies\nis disturbed it is only restored more or less slowly. Sometimes days\nand years are required before it is regained. Scarcely do they attain\nthis relative repose when they are again disturbed, for the environment\nitself is not fixed; it experiences variations which react in their\nturn upon the body under consideration; and it is only at the end of\nthese variations, at the end of their respective periods, that they\nwill attain together, in a universal uniformity, an eternal repose.\n\nWe shall see that metallic alloys undergo continual physical and\nchemical changes. They are always seeking a more or less elusive\nequilibrium. Physicists in modern times have given their attention to\nthis internal activity of material bodies, to the pursuit of stability.\nWiedemann, Warburg, Tomlinson, MM. Duguet, Brillouin, Duhem, and\nBouasse have revived the old experimental researches of Coulomb and\nWertheim on the elasticity of bodies, the effects of pressures and\nthrusts, the hammering, tempering, and annealing of metals.\n\nThe internal activity manifested under these circumstances presents\nquite remarkable characteristics which cannot but be compared to the\nanalogous phenomena presented by living bodies. Thus have arisen even\nin physics, a figurative terminology, and metaphorical expressions\nborrowed from biology.\n\n_Comparison of the Activity of Particles with Vital Activity._\u2014Since\nLord Kelvin first spoke of the _fatigue_ of metals, or the _fatigue_\nof elasticity, Bose has shown in these same bodies the fatigue of\nelectrical contact. The term _accommodation_ has been employed in the\nstudy of torsion, and according to Tomlinson for the very phenomena\nwhich are the inverse of those of fatigue. The phenomena presented by\nglass when acted on by an external force which slowly bends it, have\nbeen called facts of adaptation. The manner in which a bar of steel\nresists wire-drawing has been compared to _defensive_ processes against\nthreatened rupture. And M. C. E. Guillaume speaks somewhere of \u201cthe\nheroic resistance of the bar of nickel-steel.\u201d The term \u201cdefence\u201d has\nalso been applied to the behaviour of chloride or iodide of silver when\nexposed to light.\n\nThere has been no hesitation in using the term \u201cmemory\u201d concurrently\nwith that of hysteresis to designate the behaviour of bodies acted\non by magnetism or by certain mechanical forces. It is true that\nM. H. Bouasse protests in the name of the physico-mathematicians\nagainst the employment of these figurative expressions. But has he not\nhimself written \u201ca twisted wire is a wound-up watch,\u201d and elsewhere,\n\u201cthe properties of bodies depend at every moment upon all anterior\nmodifications\u201d? Does not this imply that they retain in some manner the\nimpression of their past evolution? Powerful deformative agencies leave\na trace of their action; they modify the body\u2019s condition of molecular\naggregation, and some physicists go so far as to say that they even\nmodify its chemical constitution. With the exception of M. Duhem, the\ndisciples of the mechanical school who have studied elasticity admit\nthat the effect of an external force upon a body depends upon the\nforces which have been previously acting on it, and not merely upon\nthose which are acting on it at the present moment. Its present state\ncannot be anticipated, it is the recapitulation of preceding states.\nThe effect of a torsional force upon a new wire will be different from\nthat of the same force upon a wire previously subjected to torsions\nand detorsions. It was with reference to actions of this kind that\nBoltzmann, in 1876, declared that \u201ca wire that has been twisted or\ndrawn out remembers for a certain time the deformations which it has\nundergone.\u201d This memory is obliterated and disappears after a certain\ndefinite period. Here then, in a problem of static equilibrium, we find\nintroduced an unexpected factor\u2014time.\n\nTo sum up, it is the physicists themselves who have indicated the\ncorrespondence between the condition of existence in many brute bodies\nand that in many living bodies. It cannot be expected that these\nanalogies will in any way serve as explanations. We should rather\nseek to derive the vital from the physical phenomenon. This is the\nsole ambition of the physiologist. To derive the physical from the\nvital phenomenon would be unreasonable. We do not attempt to do this\nhere. It is nevertheless true that analogies are of service, were it\nonly to shake the support which, from the time of Aristotle, has been\naccorded to the division of the bodies of nature into _psuchia_ and\n_apsuchia_\u2014_i.e._, into living and brute bodies.\n\n\n \u00a7 2. THE BROWNIAN MOVEMENT.\n\n\n_The Existence of the Brownian Movement._\u2014The simplest way of judging\nof the working activity of matter is to observe it when the liberty of\nthe particles is not interfered with by the action of the neighbouring\nparticles. We approximate to this condition when we watch, through the\nmicroscope, grains of dust suspended in a liquid, or globules of oil\nsuspended in water. Now what we see is well known to all microscopists.\nIf the granulations are sufficiently small, they seem to be never at\nrest. They are animated by a kind of incessant tremor; we see the\nphenomena called the \u201cBrownian movement.\u201d This movement has struck\nall observers since the invention of the magnifying glass or simple\nmicroscope. But the English botanist, Brown, in 1827, made it the\nobject of special research and gave it his name. The exact explanation\nof it remained for a long time obscure. It was given in 1894 by M.\nGouy, the learned physicist of the Faculty of Lyons.\n\nThe observer who for the first time looks through the microscope at\na drop of water from the river, from the sea, or from any ordinary\nsource\u2014that is to say, water not specially purified\u2014is struck with\nsurprise and admiration at the motion revealed to him. Infusoria,\nmicroscopic articulata, and various micro-organisms people the\nmicroscopic field, and animate it by their movements; but at the same\ntime all sorts of particles are also agitated, particles which cannot\nbe considered as living beings, and which are, in fact, nothing but\norganic detritus, mineral dust, and debris of every description. Very\noften the singular movements of these granulations, which simulate up\nto a certain point those of living beings, have perplexed the observer\nor led him to erroneous conclusions, and the bodies have been taken for\nanimalcules or for bacteria.\n\n_Characters of this Movement._\u2014But it is as a rule quite easy to avoid\nthis confusion. The Brownian movement is a kind of oscillation, a\nstationary, dancing to-and-fro movement. It is a Saint Vitus\u2019s dance\non one and the same spot, and is thus distinguished from the movements\nof displacement customary with animate beings. Each particle has its\nown special dance. Each one acts on its own account, independently of\nits neighbour. There is, however, in the execution of these individual\noscillations a kind of common and regular character which arises from\nthe fact that their amplitudes differ little from each other. The\nlargest particles are the slowest; when above four thousandths of a\nmillimetre in diameter, they almost cease to be mobile. The smallest\nare the most active. When so small as to be barely visible in the\nmicroscope, the movement is extremely rapid, and can only occasionally\nbe perceived. It is probable that it would be still more accelerated in\nsmaller objects; but the latter will always escape our observation.\n\n_Its Independence of the Nature of the Bodies and of the\nEnvironment._\u2014M. Gouy remarked that the movement depends neither on the\nnature nor on the form of the particles. Even the nature of the liquid\nhas but little effect. Its degree of viscosity alone comes into play.\nThe movements are, indeed, more lively in alcohol or ether, which are\nvery mobile liquids; they are slow in sulphuric acid and in glycerine.\nIn water, a grain one two-thousandth of a millimetre in diameter\ntraverses, in a second, ten or twelve times its own length.\n\nThe fact that the Brownian movement is seen in liquors which have been\nboiled, in acids and in concentrated alkalies, in toxic solutions of\nall degrees of temperature, shows conclusively that the phenomenon\nhas no vital significance; that it is in no way connected with vital\nactivity so called.\n\n_Its Indefinite Duration._\u2014The most remarkable character of this\nphenomenon is its permanence, its indefinite duration. The movement\nnever ceases, the particles never attain repose and equilibrium.\nGranitic rocks contain quartz crystals which, at the moment of their\nformation, include within a closed cavity a drop of water containing\na bubble of gas. These bubbles, contemporary with the Plutonian age\nof the globe, have never since their formation ceased to manifest the\nBrownian movement.\n\n_Its Independence of External Conditions._\u2014What is the cause of this\neternal oscillation? Is it a tremor of the earth? No! M. Gouy saw the\nBrownian movement far away from cities, where the mercurial mirror of\na seismoscope showed no subterranean vibration. It does not increase\nwhen the vibrations occur and become quite appreciable. Neither is\nit changed by variation in light, magnetism, or electric influences;\nin a word, by any external occurrences. The result of observation\nis to place before us the paradox of a phenomenon which is kept up\nand indefinitely perpetuated in the interior of a body without known\nexternal cause.\n\n_The Brownian Movement must be the First Stage of Molecular\nMotion._\u2014When we take in our hands a sheet of quartz containing a\ngaseous inclusion, we seem to be holding a perfectly inert object. When\nwe have placed it upon the stage of the microscope, and have seen the\nagitation of the bubble, we are convinced that this seeming inertia is\nmerely an illusion.\n\nRepose exists only because of our limited vision. We see the objects as\nwe see from afar a crowd of people. We perceive them only as a whole,\nwithout being able to discern the individuals or their movements.\nA visible object is, in the same way, a mass of particles. It is a\nmolecular crowd. It gives us the impression of an indivisible mass, of\na block in repose.\n\nBut as soon as the lens brings us near to this crowd, as soon as the\nmicroscope enlarges for us the minute elements of the brute body,\nthen they appear to us, and we perceive the continual agitation of\nthose elements which are less than four thousandths of a millimetre\nin diameter. The smaller the particles under consideration, the more\nlively are their movements. From this we infer that if we could\nperceive molecules, whose probable dimensions are about one thousand\ntimes less, their probable velocity would be, as required by the\nkinetic theory, some hundreds of metres per second. In the case of\nobjects we can only just see, the Brownian velocity is only a few\nthousandths of a millimetre per second. No doubt, concludes M. Gouy,\nthe particles that show this velocity are really enormous when compared\nwith true molecules. From this point of view the Brownian movement\nis but the first degree, and a magnified picture of the molecular\nvibrations assumed in the kinetic theory.\n\n\n \u00a7 3. THE INTERNAL ACTIVITY OF BODIES.\n\n\n_Migration of Material Particles._\u2014In the Brownian movement we\ntake into account only very small, isolated masses, small free\nfragments\u2014_i.e._, material particles which are not hampered by their\nrelations to neighbouring particles. Any one but a physicist might\nbelieve that in true solids endowed with cohesion and tenacity, in\nwhich the molecules were bound one to the other, in which form and\nvolume are fixed, there could be no longer movements or changes. This\nis a mistake. Physics teaches us the contrary, and, in late years\nespecially, has furnished us characteristic examples. There are real\nmigrations of material particles throughout solid bodies\u2014migrations\nof considerable extent. They are accomplished through the agency\nof diverse forces acting externally\u2014pressures, thrusts, torsions;\nsometimes under the action of light, sometimes under the action of\nelectricity, sometimes under the influence of forces of diffusion.\nThe microscopic observation of alloys by H. and A. Lechatelier, J.\nHopkinson, Osmond, Charpy, J. R. Benoit; researches into their physical\nand chemical properties by Calvert, Matthiessen, Riche, Roberts Austen,\nLodge, Laurie, and C. E. Guillaume; experiments on the electrolysis\nof glass, and the curious results of Bose upon electrical contact of\nmetals, show in a striking manner the chemical and kinetic evolutions\nwhich occur in the interior of bodies.\n\n_Migration under the Action of Weight._\u2014An experiment by Obermeyer,\ndating from 1877, furnishes a good example of the motions of solid\nbodies through a hardened viscid mass, taking place under the influence\nof weight. The black wax that shoemakers and boatbuilders use, is a\nkind of resin extracted from the pine and other resinous trees, melted\nin water, and separated from the more fluid part which rises from it.\nIts colour is due to the lampblack produced by the combustion of straw\nand fragments of bark. At an ordinary temperature it is a mass so hard\nthat it cannot always be easily scratched by the finger-nail; but if it\nis left to itself in a receptacle, it finally yields, spreads out as\nif it were a liquid, and conforms to the shape of the vessel. Suppose\nwe place within a cavity hollowed out of a piece of wood a portion of\nthis substance, and keep it there by means of a few pebbles, having\npreviously placed at the bottom of the cavity a few fragments of some\nlight substance, such as cork. The piece of wax is thus between a light\nbody below and a heavy body above. If we wait a few days, this order\nis reversed\u2014the wax has filled the cavity by conforming to it; the\ncork has passed through the wax and appears on the surface, while the\nstones are at the bottom. We have here the celebrated experiment of the\nflask with the three elements, in which are seen the liquids mercury,\noil, and water superposed in the order of their density, but in this\ncase demonstrated with solid bodies.\n\n_Influence of Diffusion._\u2014Diffusion, which disseminates liquids\nthroughout each other, may also cause solids to pass through other\nsolids. Of this W. Roberts Austen gave a convincing proof. This\ningenious physicist placed a little cylinder of lead upon a disc of\ngold, and kept the whole at the temperature of boiling water. At this\ntemperature both metals are perfectly solid, for the melting point of\ngold is 1,200\u00b0 C., and of lead is 330\u00b0. Still, after this contact has\nbeen prolonged for a month and a half, analysis shows that the gold has\nbecome diffused through the top of the cylinder of lead.\n\n_Influence of Electrolysis._\u2014Electrolysis offers another no less\nremarkable means of transportation. By its means we may force metals,\nsuch as sodium or lithium, through glass walls. The experiment may be\nperformed as indicated by M. Charles Guillaume. A glass bulb containing\nmercury is placed in a bath of sodium amalgam, and a current is then\nmade to pass from within outward. After some time it can be shown that\nthe metal has penetrated the wall of the bulb, and has become dissolved\nwithin it.\n\n_Influence of Mechanical Pressure._\u2014Mechanical pressure is also capable\nof causing one metal to pass into another. We need not recall the\nwell-known experiment of Cailletet, who, by employing considerable\npressure, caused mercury to sweat through a block of iron. In a more\nsimple manner W. Spring showed that a disc of copper could be welded\nto a disc of tin by pressing them strongly one against the other. Up to\na certain distance from the surfaces of contact a real alloy is formed;\na layer of bronze of a certain thickness unites the two metals, and\nthis could not take place did not the particles of both metals mutually\ninterpenetrate.\n\n\n \u00a7 4. INTERNAL ACTIVITY OF ALLOYS.\n\n\n_Structure of Alloys._\u2014Metallic alloys have a remarkable structure,\nwhich is essentially mobile, and which we have only now begun to\nunderstand by the aid of the microscope. Microscopical examination\njustifies to a certain degree Coulomb\u2019s conjecture. That illustrious\nphysicist explained the physical properties of metals by imagining them\nto be formed of two kinds of elements\u2014integral particles, to which\nthe metal owes its elastic properties, and a _cement_ which binds the\nparticles, and to which it owes its coherence. M. Brillouin has also\ntaken up this hypothesis of duality of structure. The metal is supposed\nto be formed of very small, isolated, crystalline grains, embedded in\nan almost continuous network of viscous matter. A more or less compact\nmass surrounding more or less distinct crystals is the conception which\nmay be formed of an alloy.\n\n_Changes of Structure produced by Deforming Agencies._\u2014It has been\nshown that profound changes of crystalline structure can be produced\nby various mechanical means, such as hammering, and the stretching\nof metallic bars carried to the point of rupture. Some of these\nchanges are very slow, and it is only after months and years that\nthey are completed, and the metal attains the definite equilibrium\ncorresponding to the conditions to which it is exposed. Though there\nmay be discussions concerning the extent of the transformations to\nwhich it is subjected, though some believe they affect the chemical\ncondition of the alloy, while others limit its power to physical\neffects, it is nevertheless true\u2014and this brings us back to our\nsubject\u2014that the mass of these metals is at work, and that it only\nslowly attains the phase of complete repose.\n\n_The Slow Re-establishment of Equilibrium. Residual Effect._\u2014These\noperations by which the physical characters of metals are changed, and\nby which they are adapted to a variety of industrial needs\u2014compression,\nhammering, rolling, stretching, and torsion\u2014have an immediate, very\napparent effect; but they have also a consecutive effect, slowly\nproduced, much less marked and less evident. This is the \u201cresidual\neffect,\u201d or \u201cNachwirkung\u201d of the Germans. It is not without importance,\neven in practical applications.\n\nHeat also creates a kind of _forced equilibrium_. This becomes but\nslowly modified, so that a body may remain for a long time in a state\nwhich is, however, not the most stable for the conditions under which\nit is considered. The number of these bodies _not in equilibrium_ is as\ngreat as that of the substances which have been exposed to fusion. All\nthe Plutonic rocks are in this condition. Glass presents a condition of\nthe same kind. Thermometers placed in melting ice do not always mark\nthe zero Centigrade. This displacement of the zero point falsifies all\nrecords if care is not taken to correct it. The correction usually\nrequires prolonged observation. The theory of the displacement of the\nthermometric zero is not entirely established; but we may suppose,\nwith the author of the _Trait\u00e9 de Thermom\u00e9trie_, that in glass, as\nin alloys, are to be found compounds which vary according to the\ntemperature. At each temperature glass tends to assume a determinate\ncomposition and a corresponding state of equilibrium; but the previous\ntemperature to which it has been subjected clearly has an influence\non the rapidity with which it attains its state of repose. The effect\nof variation is more marked when we observe glass of more complicated\ncomposition. We can understand that those which contain comparable\nquantities of the two alkalies, soda and potash, may be more subject to\nthese modifications than those having a more simple composition based\non a single alkali.\n\n_Effects of Annealing._\u2014A piece of brass wire that has been drawn and\nthen heated is the scene of certain very remarkable internal changes,\nand these have been only recently recognized. The violent treatment\nof the metallic thread in forcing it through the hole in the die has\ncrushed the crystalline particles; the interior state of the wire is\nthat of broken crystals embedded in a granular mass. Heating changes\nall that. The crystals separate, repair themselves, and are built\nup again; they are then hard, geometrical bodies, in an amorphous,\nrelatively soft and plastic mass; their number keeps on increasing;\nequilibrium is not established until the entire mass is crystallized.\nWe may imagine how many displacements, enormous when compared with\ntheir dimensions, the molecules have to undergo when passing through\nthe resisting mass, and arranging themselves in definite places in the\ncrystalline structures.\n\nIn the same way, too, in the manufacture of steel, the particles of\ncoal at first applied to the surface pass through the iron.\n\nThis _faculty of molecular displacement_ enables the metal in some\ncases to modify its state at one point or another. The use made of this\nfaculty under certain circumstances is very curious, greatly resembling\nthe adaptation of an animal to its environment, or the methods of\ndefence against agents that might destroy it.\n\n_Effect of Stretching. Hartmann\u2019s Experiment._\u2014When a cylindrical\nrod of metal, held firmly at either end\u2014a test-piece, as it is\ncalled in metallurgy\u2014is pulled sufficiently hard, it often elongates\nconsiderably, part of the elongation disappearing as soon as the strain\nceases, and the other part remaining. The total elongation is thus the\nsum of an \u201celastic elongation,\u201d which is temporary, and a \u201cpermanent\nelongation.\u201d If we continue the stretching, there appears at some point\nof the rod a local extension with contraction of sectional area. It is\nhere that the rod will break.\n\nBut in place of continuing the stretching, Mr. Hartmann suspends it.\nHe stops, as if to give the \u201cmetal-being\u201d time to rally. During this\ndelay it would seem that the molecules hasten to the menaced point\nto reinforce and harden the weak part. In fact the metal, which was\nsoft at other points, at this spot looks like tempered metal. It is no\nlonger extensible.\n\nWhen the experimenter begins the stretching again after this rest, and\nafter the narrowed bar has been rolled and become cylindrical again,\nthe local extension and sectional contraction is forced to occur at\nanother point. If another rest is given at this point the metal will\nalso become hardened.\n\nIf we repeat the experiment a sufficient number of times, we shall find\na total transformation of the rod, which becomes hardened throughout\nits entire extent. It will break rather than elongate if the stretching\nis sufficiently severe.\n\n_Nickel Steels\u2014their \u201cHeroic\u201d Resistance._\u2014Nickel steels present this\nphenomena in an exaggerated degree. The alternation of operations which\nwe have just described, bringing the various parts of an ordinary\nsteel rod into a tempered state, is not necessary with nickel steel.\nThe effect is produced in the course of a single trial. As soon as\nthere is any tendency to contraction the alloy hardens at that precise\nplace; the contraction is hardly noticeable; the movement is stopped at\nthis point to attack another weak point, stops there again and attacks\na third, and so on; and, finally, the paradoxical fact appears that\na rod of metal which was in a soft state and could be considerably\nelongated has now become throughout its whole extent as hard, brittle,\nand inextensible as tempered steel. It is in connection with this point\nthat M. C. E. Guillaume spoke of \u201cheroic resistance to rupture.\u201d It\nwould seem, in fact, as if the ferro-nickel bar had reinforced each\nweak point as it was threatened. It is only at the end of these efforts\nthat the inevitable catastrophe occurs.\n\n_Effect of Temperature._\u2014When the temperature changes, it is seen that\nthese ferro-nickel bars elongate or retract, modifying at the same time\ntheir chemical constitution. But these effects, like those which occur\nin the glass bulb of a thermometer, do not occur at once. They are\nproduced rapidly for one part, and more slowly for a small remaining\nportion. Bars of ferro-nickel which have been kept at the same\ntemperature change gradually in length in the course of a year. Can\nwe find a better proof of internal activity occurring in a substance\ndiffering so greatly from living matter?\n\n_Nature of the Activity of Particles._\u2014These are examples of the\ninternal activity that occurs in brute bodies. Besides, these facts\nthat we are quoting merely to refute Bichat\u2019s assertion relative to\nthe immutability of brute bodies, and to show us their activity, also\nafford us another proof. They show that this activity, like that of\nanimals, wards off foreign intervention, and that this parrying of\nthe attack, again like that of animals, is adapted for the defence\nand preservation of the brute mass. So that if we consider of special\nimportance the adaptative, teleological characteristic of vital\nphenomena, a characteristic which is so easily made too much of in\nbiological interpretations, we may also find it again in the inanimate\nworld. To this end we may add to the preceding examples one more which\nis no less remarkable. This is the famous case of Becquerel\u2019s process\nfor colour-photography.\n\n_Colour-Photography._\u2014A greyish plate, treated with chloride or iodide\nof silver and exposed to a red light, rapidly becomes red. It is then\nexposed to green light, and after passing through dull and obscure\ntints it becomes green. To explain this remarkable phenomenon, we\ncannot improve on the following statement:\u2014The silver salt protects\nitself against the light that threatens its existence; that light\ncauses it to pass through all kinds of stages of coloration before\nreducing it; the salt stops at the stage which protects it best. It\nstops at red, if it is red light that assails it, because in becoming\nred by reflection it best repels that light\u2014_i.e._, it absorbs it the\nleast.\n\nIt may then be advantageous, for the comprehension of natural\nphenomena, to regard the transformation of inanimate matter as\nmanifestations of a kind of internal life.\n\n_Conclusion. Relations of the Surrounding Medium to the Living Being\nand the Brute Body._\u2014Brute bodies, then, are not immutable any more\nthan are living bodies. Both depend on the medium that surrounds them,\nand they depend upon it in the same way. Life brings together, brings\ninto conflict, an appropriate organism and a suitable environment.\nAuguste Comte and Claude Bernard have taught us that vital phenomena\nresult from the reciprocal action of these two factors which are\nin close correlation. It is also from the reciprocal action of the\nenvironment and the brute body that inevitably result the phenomena\nwhich that body presents. The living body is sometimes more sensitive\nto variations of the ambient medium than is the brute body, but at\nother times the reverse is the case. For example, there is no living\norganism as impressionable to any kind of stimulus whatever as the\nbolometer is to the slightest variations of temperature.\n\nThere can only be, then, one chemically immutable body\u2014namely, the atom\nof a simple body, since, by its very definition, it remains unaltered\nand intangible in combinations. This notion of an unalterable atom\nhas, however, itself been attacked by the doctrine of the ionization\nof particles due to Sir J. J. Thomson; and besides, with very few\nexceptions\u2014those of cadmium, mercury, and the gases of the argon\nseries\u2014the atoms of simple bodies cannot exist in a free state.\n\nThus, as in the vital struggle, the ambient medium by means of\nalimentation furnishes to the living being, whether whole or\nfragmentary, the materials of its organization and the energies which\nit brings into play. It also furnishes to brute bodies their materials\nand their energies.\n\nIt is also said that the ambient medium furnishes to the living being\na third class of things, the _stimuli_ of its activities\u2014_i.e._, its\n\u201cprovocation to action.\u201d The protozoon finds in the aquatic environment\nwhich is its habitat the stimuli which provoke it to move and to absorb\nits food. The cells of the metazoon encounter in the same way in the\nlymph, the blood, and the interstitial liquids which bathe them, the\nshock, the stimulus which brings their energies into play. They do not\nderive from themselves, by a mysterious spontaneity without parallel in\nthe rest of nature, the capricious principle which sets them in motion.\n\nVital spontaneity, so readily accepted by persons ignorant of biology,\nis disproved by the whole history of the science. Every vital\nmanifestation is a response to a stimulus, a provoked phenomenon. It\nis unnecessary to say this is also the case with brute bodies, since\nthat is precisely the foundation of the great principle of the inertia\nof matter. It is plain that it is also as applicable to living as to\ninanimate matter.\n\n\n\n\n CHAPTER V.\n\n SPECIFIC FORM. LIVING BODIES AND CRYSTALS.\n\n \u00a7 1. Specific form and chemical constitution\u2014The wide distribution\n of crystalline forms\u2014Organization of crystals\u2014Law of relation\n between specific form and chemical constitution\u2014Value of form as a\n characteristic of brute and living beings\u2014Parentage, living beings and\n mineral parentage\u2014Iso-morphism and the faculty of cross-breeding\u2014Other\n analogies. \u00a7 2. Acquisition and re-establishment of the specific\n form\u2014Mutilation and regeneration of crystals\u2014Mechanism of reparation.\n\n\n\u00a7 1. _Specific Form and Chemical Constitution._\u2014In the enumeration\nwhich we have made of the essential features of vitality there are\nthree that are, so to speak, of the highest value. They are, in\nthe order of their importance:\u2014The possession of a specific form;\nthe faculty of growth or nutrition; and finally, the faculty of\nreproduction by generation. By restricting our comparison between\nbrute bodies and living bodies to these truly fundamental characters\nwe sensibly restrict the field, but we shall see that it does not\ndisappear.\n\n_Wide Distribution of Crystalline Forms._\u2014The consideration of specific\nforms shows us that in the mineral world we need only consider\ncrystallized bodies, as they are almost the only ones that possess\ndefinite form. In restricting ourselves to this category we do not\nlimit our field as much as might be supposed. Crystalline forms are\nvery widely distributed. They are, in a measure, universal. Matter\nhas a decided tendency to assume these forms whenever the physical\nforces which it obeys act with order and regularity, and when their\naction is undisturbed by accidental occurrences. In the same way, too,\nliving forms are only possible in regulated environments, under normal\nconditions, protected from cataclysms and convulsions of nature.\n\nThe possession of a specific form is the most significant feature of\nan organized being. Its tendency, from the time it begins to develop\nfrom the germ, is toward the acquirement of that form. The progressive\nmanner in which it seeks to realize its architectural plan in spite of\nthe obstacles and difficulties that arise\u2014healing its wounds, repairing\nits mutilations\u2014all this, in the eyes of the philosophical biologist,\nforms what is perhaps the most striking characteristic of a living\nbeing, that which best shows its unity and its individuality. This\nproperty of organogenesis seems pre-eminently the vital property. It is\nnot so, however, for crystalline bodies possess it in an almost equal\ndegree.\n\nThe parallel between the crystal and a living being has been often\ndrawn. I will not reproduce it here in detail. My sole desire, after\nsketching its principal features, is to call attention to the new\ninformation that has been brought out by recent investigations.\n\n_Organization of Crystals. Views of Ha\u00fcy, Delafosse, Bravais, and of\nWallerant._\u2014In botany, zoology, and crystallography we understand by\nform an assemblage of material constituents co-ordinated in a definite\nsystem\u2014_i.e._, the organization itself. The body of man, for example,\nis an edifice in which sixty trillion cells ought each to find its own\npredetermined place.\n\nIn crystallography also we understand by form the organization which\ncrystals present. The grouping of the elements of crystals is, perhaps,\nmore simple. They are none the less organized, in the same sense that\nliving bodies are.\n\nTheir organization, while more uniform than that of living bodies,\nstill shows a considerable amount of variation. It should not be\nassumed that the area of a crystal is completely filled, with\ncontiguous parts applied one to the other by plane faces, as might\nbe supposed from the phenomenon of cleavage which dissociates the\nparts of the crystalline body into solids of this kind. In reality,\nthe constituent parts are separated from each other by spaces. They\nare arranged in a quincunx, as Ha\u00fcy put it, or along the lines of a\nnetwork, to use the terms of Delafosse and Bravais. The intervals left\nbetween them are incomparably larger than their diameters. So that in\nthe organization of a crystal it is necessary to take into account two\nquite different things:\u2014An element, the crystalline particle, which\nis a certain aggregate of chemical molecules having a determinate\ngeometrical form; and a more or less regular, parallelopipedic network,\nalong the edges of which are arranged in a constant and definite manner\nthe aforesaid particles. The external form of the crystal indicates the\nexistence of the network. Its optical properties depend upon the action\nof the particles, as Wallerant has shown: Thus we must distinguish in\na crystal between two kinds of geometrical figures\u2014that of the network\nand that of the particle\u2014and their characters of symmetry may be either\nconcordant or discordant.\n\nThe crystalline particle, the element of the crystal, is therefore\na certain molecular complex that repeats itself identically and is\nidentically placed at the nodes of the parallelopipedic network. It has\nbeen given different names well calculated to produce confusion-the\ncrystallographic molecule of Mallard, the complex particle of other\nauthors. Some have separated this element into subordinate elements\n(the fundamental particles of Wallerant and of Lapparent).\n\nThese very general outlines will suffice to show how complex and\nadjustable is the organization of the crystalline individual, which in\nspite of its geometric regularity and its rigidity, may be compared\nwith the still more flexible organization of the living element. The\nmineral individual is more stable, more labile\u2014_i.e._, less prone\nto undergo change than is the living individual. We may say with\nM. Lapparent that \u201ccrystallized matter presents the most perfect\nand stable orderly arrangement of which the particles of bodies are\nsusceptible.\u201d\n\n_Law of Relation of Specific Form to Chemical\nConstitution._\u2014Crystallization is a method of acquiring specific form.\nThe geometrical architecture of the mineral individual is but little\nless wonderful or characteristic than that of the living individual.\nIts form is the result of the mutual reactions of its substances and\nof the medium in which it is produced; it is the condition of material\nequilibrium corresponding to a given situation. This idea of a specific\nform belonging to a given substance under given conditions must be\nborne in mind. We may consider it as a kind of principle of nature,\nan elementary law, which may serve as a point of departure for the\nexplanation of phenomena. A particular substance under identical\nconditions of environment, must always assume a certain form.\n\nThis close linking of substance and form, admitted as a postulate in\nphysical sciences, has been carried into biology by some philosophical\nnaturalists, by M. Le Dantec, for instance.\n\nLet us imitate them for a moment. Let us cease to seek in the living\nbeing for the prototype of the crystal; let us, on the contrary, seek\nin the crystal the prototype of the living being. If we succeed in\nthis, we shall then have found the physical basis of life.\n\nLet us say, then, with the biologists we have mentioned, that the\nsubstance of each living being is peculiar to it; that it is specific,\nand that its form\u2014that is to say its organization\u2014follows from it.\nThe morpholpgy of any being whatever, of an animal\u2014of a setter, for\nexample\u2014or even of a determinate being\u2014of Peter, of Paul\u2014is the\n\u201ccrystalline form of their living matter.\u201d It is the only form of\nequilibrium that can be assumed under the given conditions by the\nsubstance of the setter, of Peter, or of Paul, just as the cube is the\ncrystalline form of sea-salt. In this manner these biologists have\nsupposed that they could carry back the problem of living form to the\nproblem of living substance, and at the same time reduce the biological\nmystery to the physical mystery. I have shown above (Chap. V. pp.\n199-204) how far this idea is legitimate, and how far and with what\nrestrictions it may be welcomed and adopted.\n\n_Value of Form as a Characteristic of Living and Brute Beings._\u2014However\nthis may be, we may say, without fear of exaggeration, that the\ncrystalline form characterizes the mineral with no less precision than\nthe anatomical form characterizes the animal and the plant. In both\ncases, form\u2014regarded as a method of distribution of the parts\u2014indicates\nthe individual and allows us to diagnose it with more or less facility.\n\n_Parentage of Living Beings and Mineral Parentage._\u2014Still another\nanalogy has been noted. In animals and plants similarity in form\nindicates similarity in descent, community of origin, and proximity in\nany scheme of classification. In the same way identity of crystalline\nform indicates mineral relationship. Substances chemically analogous\nshow identical, geometrically superposable forms, and are thus arranged\nin family or generic groups recognizable at a glance.\n\n_Isomorphism and the Faculty of Cross-breeding._\u2014And further, the\npossibility in the case of isomorphous bodies, of their replacing each\nother in the same crystal during the process of formation and of thus\nmingling, so to speak, their congenital elements, may be compared\nwith the possibility of inter-breeding with living beings of the same\nspecies. Isomorphism is thus a kind of faculty of crossing. And as the\nimpossibility of crossing is the touchstone of taxonomic relationship,\ntesting it, and separating stocks that ought to be separated, so the\noperation of crystallization is also a means of separating from an\naccidental mixture of mineral species the pure forms which are blended\ntherein. Crystallization is the touchstone of the specific purity of\nminerals; it is the great process in chemical purification.\n\n_Other Analogies._\u2014The analogies between crystalline and living forms\nhave been pushed still further even to the verge of exaggeration.\n\nThe internal and external symmetry of animals and plants has been\ncompared to that of crystals. Transitions or intergradations have been\nsought between the rigid and faceted architecture of the latter and the\nflexible structure and curved surface of the former; the utricular form\nof flowers of sulphur on the one hand, and the geometrical structure\nof the shells of radiolarians on the other, have shown an exchange of\ntypical forms between the two systems. An effort has even been made\nto draw a parallel between six of the principal types of the animal\nkingdom and the six crystalline systems. If carried as far as this, our\nthesis becomes puerile. Real analogies will suffice. Among these the\ncurious facts of crystalline renewal come first.\n\n\n \u00a7 2. CICATRIZATION IN LIVING BEINGS AND IN CRYSTALS.\n\n\nWe know that living beings not only possess a typical architecture\nwhich they have themselves constructed, but that they defend it against\ndestructive agencies, and that if need arise they repair it. The\nliving organism cicatrizes its wounds, repairs losses of substance,\nregenerates more or less perfectly the parts that have been removed;\nin other terms, when it has been mutilated it tends to reconstruct\nitself according to the laws of its own morphology. This phenomenon of\nreconstitution or reintegration, these more or less successful efforts\nto re-establish its form and its integrity, at first appear to be a\ncharacteristic feature of living beings. This is not the case.\n\n_Mutilation and Re-integration of Crystals._\u2014Crystals\u2014let us say\ncrystalline individuals\u2014show a similar aptitude for repairing their\nmutilations. Pasteur, in an early work, discussed these curious facts.\nOther experimenters, Gernez a little later and Rauber more recently,\ntook up the same subject, but could do no more than extend and confirm\nhis observations. Crystals are formed from a primitive nucleus, as the\nanimal is formed from an egg; their integral particles are disposed\naccording to efficient geometrical laws, so as to produce the typical\nform by a constructive process that may be compared to the embryogenic\nprocess which builds up the body of an animal. Now this operation\nmay be disturbed by accidents in the surrounding medium or by the\ndeliberate intervention of the experimenter. The crystal is then\nmutilated. Pasteur saw that these mutilations repaired themselves.\n\u201cWhen,\u201d said he, \u201ca crystal from which a piece has been broken off\nis replaced in the mother liquor, we see that while it increases in\nevery direction by a deposit of crystalline particles, activity occurs\nat the place where it was broken off or deformed; and in a few hours\nthis suffices not only to build up the regular amount required for the\nincrease of all parts of the crystal, but to re-establish regularity\nof form in the mutilated part.\u201d In other words, the work of formation\nof the crystal is carried on much more actively at the point of lesion\nthan it would have been had there been no lesion. The same thing would\nhave occurred with a living being.\n\n_Mechanism of Reparation._\u2014Gernez some years later made known the\nmechanism of this reparation, or, at least, its immediate cause. He\nshowed that on the injured surface the crystal becomes less soluble\nthan on the other facets. This is not, however, an exceptional\nphenomenon. It is, on the contrary, quite frequently observed that the\ndifferent faces of a crystal show marked differences in solubility.\nThis is what happens in every case for the mutilated face in comparison\nwith the others; the matter is less soluble there. The consequence\nof this is clear; the growth must preponderate on that face, since\nthere the mother liquor will become super-saturated before being\nsuper-saturated for the others. We may explain this result in another\nway. Each face of the crystal in contact with the mother liquor is\nexposed to two antagonistic actions: The matter deposited upon a\nsurface may be taken away and redissolved if, for any reason whatever,\nsuch matter becomes more soluble than that of the liquid stratum in\ncontact with it; in the second place, the matter of this liquid stratum\nmay, under contrary conditions, be deposited, and thus increase the\nbody of the crystal. There is, then, for each point of the crystalline\nfacet, a positive operation of deposit which results in a gain, and a\nnegative operation of redissolution which results in a loss. One or\nthe other effect predominates according as the relative solubility is\ngreater or less for the matter of the facet under consideration. On the\nmutilated surface it is diminished, deposition then prevails.\n\nBut this is only the immediate cause of the phenomenon; and if we wish\nto know why the solubility has diminished on the mutilated surface\nOstwald explains it to us by showing that crystallization tends to form\na polyhedron in which the surface energy is a relative minimum.\n\n\n\n\nCHAPTER VI.\n\nNUTRITION IN THE LIVING BEING AND IN THE CRYSTAL.\n\n Assimilation and growth in the crystal.\u2014Methods of growth\n in the crystal and in the living being; intussusception;\n apposition.\u2014Secondary and unimportant character of the process of\n intussusception.\n\n\nI have already stated (Chap. VI. p. 209) that nutrition may be\nconsidered as the most characteristic and essential property of living\nbeings. Such beings are in a state of continual exchange with the\nsurrounding medium. They assimilate and dissimilate. By assimilation\nthe substance of their being increases at the expense of the\nsurrounding alimentary material, which is rendered similar to that of\nthe being itself.\n\n_Assimilation and Growth in the Crystal._\u2014There exists in the crystal\na property analogous to nutrition, a kind of nutrility, which is\nthe rudiment of this fundamental property of living beings. The\ndevelopment of a crystal starts from a primitive nucleus, the germ\nof the crystalline individual that we will presently compare to\nthe ovum or embryo of a plant or an animal. Placed in a suitable\nculture-medium\u2014_i.e._, in a solution of the substance\u2014this germ\ndevelops. It assimilates the matter in solution, incorporates the\nparticles of it, and increases, preserving at the same time its form,\nreproducing its specific type or a variety of it. Its growth proceeds\nwithout interruption. The crystalline individual may attain quite a\nlarge size if we know how to nourish it properly\u2014we might say, to\nfatten it. Very frequently, at a given time, a new particle of the\ncrystal serves in its turn as a primitive nucleus, and becomes the\npoint of departure for a new crystal engrafted upon the first.\n\nTaken from its mother liquor, placed where it cannot be nourished,\nthe crystal, arrested in its growth, falls into a condition of rest\nnot without analogy to that of a seed or of a reviviscent animal. Its\nevolution is resumed with the return of favourable conditions\u2014the bath\nof soluble matter.\n\nThe crystal is in a relation of continual exchange with the surrounding\nmedium which feeds it. These exchanges are regulated by the state of\nthis medium, or, more exactly, by the state of the liquid stratum\nwhich is in immediate contact with the crystals. It loses or it gains\nin substance if, for example, this layer becomes heated or cooled\nmore rapidly than the crystal. In a general way, it assimilates or\ndissimilates according as its immediate environment is saturated or\ndiluted. Here, then, we have a kind of mobile equilibrium, comparable,\nin some measure, to that of the living being.\n\n_Methods of Growth of the Crystal and of the Living Being.\nIntussusception. Apposition._\u2014In truth, there seems to be a complete\nopposition between the crystal and the living being as regards\ntheir manner of nutrition and growth. In the one case the method\nis intussusception; in the other it is apposition. The crystalline\nindividual is all surface. Its mass is impenetrable to the nutritive\nmaterials. Since only the surface is accessible, the incorporation of\nsimilar particles is possible only by external juxtaposition, and the\nedifice increases only because a new layer of stones has been added to\nthose which were there before. On the contrary, the body of an animal\nis a mass essentially penetrable. The cellular elements that compose\nit have more or less rounded and flexible forms. Their contact is by\nno means perfect. They have neither the stiffness nor the precision\nof adjustment that the crystalline particles have. Liquids and gases\ncan insinuate themselves from without and circulate within the meshes\nof this loose construction. Assimilation can therefore take place\nthroughout its whole depth, and the edifice increases because each\nstone is itself increasing.\n\n_The Secondary and Commonplace Character of the Process of\nIntussusception._\u2014The apparent opposition of these two processes is\ndoubtless diminished if we compare the simple mineral individual\nwith the elementary living unit, the crystalline particle with the\nprotoplasmic mass of a cell. Without carrying analysis so far as\nthis, it is yet easy to see that apposition and intussusception are\nmechanical means that living beings employ at one and the same time and\ncombine according to their necessities. The hard parts of the internal\nand external skeleton increase both by interposition and superposition,\nat once. It is by the last method that bones increase in diameter,\nand the shells of molluscs, the scales of reptiles and fishes, and\nthe testae of many radiate animals are formed. In these organs, as in\ncrystals, life and nutrition occur at the surface.\n\nApposition and intussusception are then secondary, mechanical\narrangements having relation to the physical characters of the\nbody\u2014solidity in the crystal, semi-fluidity in the cellular protoplasm.\nIf we compare the inorganic liquid matter with the semi-fluid organized\nmatter, we recognize that the addition of substance takes place in\nthe same manner in each\u2014_i.e._, by interposition. If we add a soluble\nsalt to a fluid, the molecules of the salt separate themselves and\ninterpose themselves between those of the fluid. There is, therefore,\nnothing especially mysterious or particularly vital about the process\nof intussusception. Applied to fluid protoplasm, it is merely the\ndiffusion that ordinarily occurs in mixed liquids.\n\n\n\n\nCHAPTER VII.\n\nGENERATION IN BRUTE BODIES AND LIVING BODIES. SPONTANEOUS GENERATION.\n\n Protoplasm a substance which continues\u2014Case of the\n crystal\u2014Characteristics of generation in the living being\u2014Property of\n growth\u2014Supposed to be confined to the living being\u2014Fertilization of\n micro-organisms\u2014Fertilization of crystals\u2014Sterilization of crystalline\n and living media\u2014Spontaneous generation of crystals\u2014Metastable and\n labile zones\u2014Glycerine crystals\u2014Possible extinction of a crystalline\n species\u2014Conclusion.\n\n\nWe have not yet exhausted the analogies between a crystal and the\nliving being. The possession of a specific form, the tendency to\nre-establish it by redisintegration and the existence of a kind of\nnutrition are not sufficient to constitute complete similarity. It\nstill lacks a fundamental character, that of generation. Chauffard\nsome time ago, in an attack which he made upon the physiological ideas\nof his day, aptly exhibited this weak point. \u201cLet us disregard,\u201d\nhe said, \u201cthose interesting facts relative to the acquisition of a\ntypical form\u2014facts that are common to the mineral world as well as\nto living beings. It is none the less true that the crystalline type\nis in no way derived from other pre-existing types, and that nothing\nin crystallization recalls the actions of ascendants and the laws of\nheredity.\u201d\n\nThis gap has since been filled. The work of Gernez, of Violette, of\nLecoq de Boisbaudran, the experiments of Ostwald and of Tammann, the\nobservations of Crookes and of Armstrong\u2014all this series of researches,\nso lucidly summarized by M. Leo Errera in his essays in botanical\nphilosophy, had for their result the establishment of an unsuspected\nrelation between the processes of crystallization and those of\ngeneration in animals and plants.\n\n_Protoplasm is a Substance which Continues. The Case of the\nCrystal._\u2014Under present conditions a living being of any kind springs\nfrom another living being similar to itself.\n\nIts protoplasm is always a continuation of the protoplasm of an\nancestor. It is an atavic substance of which we do not see the\nbeginning; we only see it continue. The anatomical element comes from a\npreceding anatomical element, and the higher animal itself comes from\na pre-existing cell of the material organism, the ovum. The ladder of\nfiliation reaches back indefinitely into the past.\n\nWe shall see that there is something analogous to this in certain\ncrystals. They are born of a preceding individual; they may be\nconsidered as the posterity of the antecedent crystal. If we speak of\nthe matter of a crystal as the matter of a living being is spoken of,\nin cases of this kind we would say that the crystalline substance is an\natavic substance of which we see only the continuation, as in the case\nof protoplasm.\n\n_Characters of Generation in the Living Being._\u2014Growth of the living\nsubstance, and consequently of the being itself, is the fundamental\nlaw of vitality. Generation is the necessary consequence of growth (p.\n210).\n\nLiving elements or cells cannot subsist indefinitely without increasing\nand multiplying. The time must come when the cell divides, either\ndirectly or indirectly; and then, instead of one cell, there are\ntwo. This is the method of generation for the anatomical element.\nIn a complex individual it is a more or less restricted part of the\norganism, usually a simple sexual cell, that takes on the formation\nof the new being, and assures the perpetuity of the protoplasm, and\ntherefore of the species.\n\n_Property of Growth. Its Supposed Restriction to Living Beings._\u2014At\nfirst it would appear that nothing like this occurs in inanimate\nnature. The physical machine, if we furnish it matter and energy, could\ngo on working indefinitely, without being compelled to increase and\nreproduce. Here, then, there is an entirely new condition peculiar to\nthe organized being, a property well adapted, it would seem\u2014and this\ntime without any possible doubt\u2014for separating living matter from brute\nmatter. It is not so.\n\nIt would not be impossible to imagine a system of chemical bodies\norganized like the animal or vegetable economy, so that a destruction\nwould be compensated for by a growth. The only thing impossible is to\nsuppose, with M. le Dantec, a destruction that would at the same time\nbe an analysis. And an additional perplexity occurs when he supposes\nthat in the successive acts exchanges of material may occur.\n\nThere is no necessity for making this impossible chemistry a\ncharacteristic of the living being. The chemistry of the living being\nis general chemistry. Lavoisier and Berthelot enforced this view. We\nshould not lose sight of the teachings of the masters.\n\nLet us return to generation, properly so called, and find in it the\ncharacteristics of brute bodies and of crystals.\n\n_The Sowing of Micro-organisms._\u2014When a microbiologist wishes to\npropagate a species of micro-organisms, he places in a culture medium\na few individuals (one is all that is actually necessary), and soon\nobserves their rapid multiplication. Usually, if only the ordinary\nmicrobes in atmospheric dust are wanted, the operator need not trouble\nto charge the culture; if the culture tube remains open and the medium\nis suitably chosen, some germ of a common species will fall in and the\nliquid will become colonized. This has the appearance of spontaneous\ngeneration.\n\n_The Sowing of Crystals._\u2014Concentrated solutions of various substances,\nsupersaturated solutions of sodium magnesium sulphate, and sodium\nchlorate are also wonderful culture media for certain mineral organic\nunits\u2014certain crystalline germs. Ch. Dufour, experimenting with water\ncooled below 0\u00b0 C., its point of solidification; Ostwald, with salol\nkept below 39\u00b0.5, its point of fusion; Tammann, with betol, which\nmelts at 96\u00b0; and, before them, Gernez, with melted phosphorus and\nsulphur\u2014all these physicists have shown that liquids in superfusion are\nalso media specially appropriate for the culture and propagation of\ncertain kinds of crystalline individuals.\n\nSome of these facts have become classic. Lowitz showed in 1785 that a\nsolution of sodium sulphate could be concentrated by evaporation so\nas to contain more salt than was conformable with the temperature,\nwithout, however, depositing the excess. But if a solid fragment, a\ncrystal of salt, is thrown into the liquor, the whole of the excess\nimmediately passes into the state of a crystallized mass. The first\ncrystal has engendered a second similar to itself; the latter has\nengendered a third, and so on from one to the other. If we compare\nthis phenomenon with that of the rapid multiplication of a species of\nmicrobes in a suitable culture medium, no difference will be perceived.\nOr perhaps we may note one unimportant difference\u2014the rapidity of\nthe propagation of the crystalline germs as opposed to the relative\nslowness of the generation of the micro-organisms.\n\nAgain, the propagation of crystallization in a supersaturated\nor superfused liquid may be delayed by appropriate devices. The\ncrystalline individual gives birth, then, to another individual that\nconforms to its own type, or even to varieties of that type when such\nexist. Into the right branch of a U tube filled with sulphur in a state\nof superfusion Gernez dropped octahedric crystals of sulphur, and into\nthe left branch prismatic crystals. On either side were produced new\ncrystals conforming to the type that had been sown.\n\n_Sterilization of Crystalline Media and Living Media._\u2014Ostwald varied\nthese experiments by using salol. He melted the substance by heating\nit above 39\u22195\u00b0C.; then, protecting it from crystals of any kind, he\nlet the solution stand in a closed tube. The salol remained liquid\nindefinitely\u2014until it was touched with a platinum wire that had been\nin contact with solid salol\u2014_i.e._, until a crystalline germ was\nintroduced. But if the platinum wire has been previously sterilized by\npassing it, as the bacteriologists do, through a flame, it can then be\nintroduced into the liquor with impunity.\n\n_The Dimensions of Crystalline Germs Comparable to those of\nMicrobes._\u2014We may dilute the solid salol with inert powder\u2014lactin,\nfor example\u2014dilute the first mixture with a second, the second with a\nthird, and so on; then, throwing into the solution of surfused salol\na tenth of a milligram from one of these various mixtures, we find\nthat the production of crystals will not take place if the fragment\nthrown in weighs less than a millionth of a milligram, or measures\nless than ten thousandths of a millimetre in length. It would seem,\nthen, that these are the dimensions of the crystalline particle or\ncrystallographic molecule of salol. In the same way Ostwald satisfied\nhimself that the crystalline germ of hyposulphite of soda weighs\nabout a thousand-millionth of a milligram, and measures a thousandth\nof a millimetre; that of chlorate of soda weighs a ten-millionth of\na milligram. These dimensions are entirely comparable with those of\nmicrobes.\n\nAll these phenomena have been studied with a detail into which it\nis impossible to enter here, and which clearly shows more and more\nintimate analogies between the formation of crystals and the generation\nof micro-organisms.\n\n_Extension and Propagation of Crystallization. Optimum Temperature\nof Incubation._\u2014Crystallization which has commenced around a germ is\npropagated more or less rapidly, and ends by invading the whole of the\nliquor.\n\nThe rapidity of this movement of extension depends upon the conditions\nof the medium, especially upon its temperature. This is shown very\nwell by Tammann\u2019s experiments with betol. This body, the salicylic\nester of naphthol, fuses at 96\u00b0 C. If it is melted in tubes sealed\nat a temperature of 100\u00b0 C., it may be cooled to lower and lower\ntemperatures\u2014to + 70\u00b0, to + 25\u00b0, to + 10\u00b0, to-5\u00b0 without solidifying.\nLet us suppose that by some combination of circumstances a few centres\nof crystallization\u2014that is to say, of crystalline germs\u2014have appeared\nin the solution. Solidification will extend slowly at the ordinary\ntemperature, at 20\u00b0 to 25\u00b0 and thereabouts. On the other hand, it will\nbe propagated with great rapidity if the liquor is kept at about 70\u00b0.\nThis point\u201470\u00b0\u2014is the thermal optimum for the propagation of germs.\nIt is the most favourable temperature for what may be called their\nincubation. As soon as the germs find themselves in a liquor at 70\u00b0\nthey increase, multiply, and show that they are in the best conditions\nfor growth.\n\n_Spontaneous Generation of Crystals. Optimum Temperature for the\nAppearance of Germs._\u2014If we consider various supersaturated solutions\nor liquids in superfusion, we shall soon discover that they can be\narranged in two categories. Some remain indefinitely liquid under\ngiven conditions unless a crystalline germ is introduced into them.\nOthers solidify spontaneously without artificial intervention, and such\ncrystallization may even be propagated very rapidly under determinate\nconditions. This implies that these are conditions favouring the\nspontaneous appearance of germs.\n\nThis distinction between substances of crystalline generation by\nfiliation and substances of spontaneous crystalline generation is not\nspecific. The same substance may present the two methods of generation\naccording to the conditions in which it is placed. Betol furnishes a\ngood example of this. Liquefy it at 100\u00b0 in a sealed tube and keep\nit by means of a stove above 30\u00b0, and it will remain liquid almost\nindefinitely. On the other hand, lower its temperature and leave it\nfor one or two minutes at 10\u00b0, and germs will appear in the liquor;\nprolong the exposure to this degree of heat and the number of these\nspontaneously appearing germs, appearing in isolation, will rapidly\nincrease. On the other hand, you will observe that propagation by\nfiliation\u2014that is to say, by extension from one to another\u2014is almost\nabsent. The temperature of 10\u00b0 is not favourable to that method of\ngeneration; and we have just seen, in fact, that it is at a temperature\nof about 70\u00b0 that extension of crystallization from one to another\nis best accomplished. The temperature of 70\u00b0 was the optimum for\npropagation by filiation. Inversely, the temperature of 10\u00b0 is the\noptimum for spontaneous generation. Above and below this optimum the\naction is slower. We may count the centres of crystallization, which\nslowly extend further and further, as in a microbic culture one counts\nthe colonies corresponding to the germs primitively formed. To sum\nup, if there is an optimum for the formation of crystals, there is a\ndifferent optimum for their rapid extension.\n\n_The Metastable and Labile Zones._\u2014This phenomena is general. There\nis for each substance a set of conditions (temperature, degree of\nconcentration, volume of the solution) in which the crystalline\nindividuals can be produced only by germs or by filiation. This is what\noccurs for betol above the temperature of 30\u00b0. The body is then in what\nOstwald has called a _metastable_ zone. There is, however, for the same\nbody another set of circumstances more or less complete, in which its\ngems appear simultaneously. This is what happens for betol at about the\ntemperature of 10\u00b0. These circumstances are those of the _labile zone_\nor zone of spontaneous generation.\n\n_Crystals of Glycerine._\u2014We may go a step further. Let us suppose, with\nL. Errera, that we have a liquid in a state of metastable equilibrium,\nwhose labile equilibrium is as yet unknown. This is what actually\noccurs for a very widely known body, glycerine. We do not know under\nwhat conditions glycerine crystallizes spontaneously. If we cool it,\nit becomes viscous; we cannot obtain its crystals in that way. It was\nnot found in crystals until 1867. In that year, in a cask sent from\nVienna to London during winter, crystallised glycerine was found,\nand Crookes showed these crystals to the Chemical Society of London.\nWhat circumstances had determined their formation? We knew not then,\nand we know not now. It may be observed that this case of spontaneous\ngeneration of the crystals of glycerine has not remained the solitary\ninstance. M. Henninger has noted the accidental formation of glycerine\ncrystals in a manufactory in St. Denis.\n\nIt may be remarked that this crystalline species appeared, as living\nspecies may have done, at a given moment in an environment in which a\nfavourable chance combined the necessary conditions for its production.\nIt is also quite comparable to the creation of a living species;\nfor having once appeared we have been able to perpetuate it. The\ncrystalline individuals of 1867 have had a posterity. They have been\nsown in glycerine in a state of superfusion, and there they reproduced\nthemselves. These generations have been sufficiently numerous to\nspread the species throughout a great part of Europe. M. Hoogewerf\nshowed a great flask full to the Dutch biologists who met at Utrecht\nin 1891. M. L. Errera presented others in June 1899, to the Society of\nMedical and Natural Sciences at Brussels. To-day the great manufactory\nof Sarg & Co., of Vienna, is engaged in their production on a large\nscale for industrial purposes.\n\nThus we are able to study this crystalline species of glycerine and to\ndetermine with precision the conditions of its continued existence. It\nhas been shown that it does not resist a temperature of 18\u00b0, so that\nif precautions were not taken to preserve it, a single summer would\nsuffice to annihilate all the crystalline individuals existing on the\nsurface of the globe, and thus the species would be extinguished.\n\n_Possible Extinction of a Crystalline Species._\u2014As these crystals\nmelt at 18\u00b0, this temperature represents the point of fusion of solid\nglycerine or the point of solidification of liquid glycerine. But the\nliquor does not solidify at all if its temperature falls below 18\u00b0 C.,\nas we well know, for it is at that temperature we use it. Nor does it\nsolidify at zero, nor even at 18\u00b0 below zero; at 20\u00b0, for instance, it\nmerely thickens and becomes pasty. We only know glycerine, then, in a\nstate of superfusion, a fact which chemists have not learned without\namazement. Under these conditions, so analogous to the appearance of\na living species, to its unlimited propagation and to its extinction,\nthe mineral world offers a quite faithful counterpart to the animal\nworld. The living body illustrates here the history of the brute body\nand facilitates its exposition. Inversely, the brute body in its\nturn throws remarkable light on the subject of the living body, and\non one of the most serious problems relative to its origin, that of\nspontaneous generation.\n\n_Conclusion._\u2014These facts lead to one conclusion. Until the concourse\nof propitious circumstances favourable to their spontaneous generation\nwas brought about, crystals were obtained only by filiation. Until the\ndiscovery of electro-magnetism, magnets were made only by filiation,\nby means of the simple or double application of a pre-existing magnet.\nBefore the discovery which fable attributes to Prometheus, every new\nfire was produced only by means of a spark from a pre-existing fire.\nWe are at the same historical stage as regards the living world,\nand that is why, up to the present, there has never been formed a\nsingle particle of living matter except by filiation, except by the\nintervention of a pre-existing living organism.\n\n\n\n\nBOOK V.\n\nSENESCENCE AND DEATH.\n\n Chap. I. The different points of view from which death may\n be regarded.\u2014Chap. II. Constitution of the organisms\u2014Partial\n death\u2014Collective death.\u2014Chap. III. Physical and chemical\n characteristics of cellular death\u2014Necrobiosis.\u2014 Chap. IV. Apparent\n perennity of complex individuals.\u2014Chap. V. Immortality of the protozoa\n and of slightly differentiated cells.\n\n\nWe grow old and we die. We see the beings which surround us grow old\nand disappear. At first we see no exceptions to this inexorable law,\nand we consider it as a universal and inevitable law of nature. But\nis this generalization well founded? Is it true that no being can\nescape the cruel fate of old age and death, to which we and all the\nrepresentatives of the higher animality are exposed? Or, on the other\nhand, are any beings immortal? Biology answers that, in fact, some\nbeings are immortal. There are beings to whose life no law assigns a\nlimit, and they are the simplest, the least differentiated and the\nleast perfect. Death thus appears to be a singular privilege attached\nto organic superiority, the ransom paid for a masterly complexity.\nAbove these elementary, monocellular, undifferentiated beings,\nwhich are protected from mortality, we find others, higher in their\norganization, which are exposed to it, but with whom death seems but\nan accident, avoidable in principle if not in fact. The anatomical\nelements of this higher animal are a case in point. Flourens once tried\nto persuade us that the threshold of old age might be made to recede\nconsiderably, and there are biologists in the present day who give us\nsome glimpse of a kind of vague immortality. We may, therefore, ask our\nreaders to follow us in our examination of these re-opened if not novel\nquestions, and we shall explain the views of contemporary physiology as\nto the nature of death, its causes, its mechanisms, and its signs.\n\n\n\n\nCHAPTER I.\n\nVARIOUS WAYS OF REGARDING DEATH.\n\n Different meanings of the word death\u2014Physiological distinction between\n elementary and general death\u2014Non-scientific opinions\u2014The ordinary\n point of view\u2014Medical point of view.\u2014The signs of death are prognostic\n signs.\n\n\n_Different Meanings of the Word Death._\u2014An English philosopher has\nasserted that the word we translate by \u201ccause\u201d has no less than\nsixty-four different meanings in Plato and forty-eight in Aristotle.\nThe word \u201cdeath\u201d has not so many meanings in modern languages, but\nstill it has many. Sometimes it indicates an action which is taking\nplace, the action of dying, and sometimes a state, the state which\nsucceeds the action of dying. The phenomena it connotes are in the eyes\nof many biologists quite different, according as we watch them in an\nanimal of complex organization, or on the other hand, in monocellular\nbeings, protozoa and protophytes.\n\n_Physiological Distinction between Elementary Death and General\nDeath._\u2014We distinguish the death of the anatomical elements,\n_elementary death_, from the death of the individual regarded as\na whole, _general death_. Hence we recognize an _apparent death_,\nwhich is an incomplete and temporary suspension of the phenomena of\nvitality, and a _real death_, which is a final and total arrest of\nthese phenomena. When we consider it in its essential nature (assumed,\nbut not known) we look on it as the _contrary of life_, as did the\nEncyclop\u00e6dia, Cuvier, and Bichat; or we regard it with others either as\nthe consequence of life, or simply as the end of life.\n\n_Non-scientific Opinions._\u2014What is death to those outside the realm of\nscience? First of all we find the consoling solution given by those\nwho believe death to be the commencement of another life. We next find\nourselves involved in a confused medley, an infinite diversity of\nphilosophical doubt and superstition. \u201cA leap into the unknown,\u201d says\none. \u201cDreamless and unconscious night,\u201d says another. And again, \u201cA\nsleep which knows no waking.\u201d Or, with Horace, \u201cthe eternal exile,\u201d or\nwith Seneca, annihilation. _Post mortem nihil; ipsaque mors nihil._\n\nThe idea which is constantly supervening in the midst of this conflict\nof opinion is that of the _breaking up_ of the elements, the union\nof which forms the living being. It has, as we shall see, a real\nfoundation which may perhaps receive the support of science. We shall\nnot find that the best way of defining death is to say that it consists\nof the \u201cdissolution of the society formed by the anatomical elements,\nor again, in the dissolution of the consciousness that the individual\npossesses of himself\u2014_i.e._, of the existence of this society.\u201d It is\nthe rupture of the social bond. The old idea of dispersion is a variant\nof the same notion. But the ancients evidently could not understand,\nas we do, the nature of these elements which are associated to form\nthe living being, and which are liberated or dispersed by death.\nWe, as biologists, can see microscopical organic unity with a real\nobjective existence. The ancients were thinking of spiritual elements,\nof principles, of entities. To the Romans, who may be said to have held\nthat there are three souls, death was produced by their separation\nfrom the body. The first, the breath, the _spiritus_, mounting towards\ncelestial regions (_astra petit_); the second, the _shade_, regaining\non the surface of the earth and wandering around the tombs; the third,\nthe _manes_, descending to the lower regions. The belief of the Hindoos\nwas slightly different. The body returned to the earth, the breath to\nthe winds, the fire of the glance to the sun, and the ethereal soul to\nthe world of the pure. Such were the ideas of mortal dispersion formed\nby ancient humanity.\n\nModern science takes a more objective point of view. It asks by\nwhat facts, by what observable events death is indicated. Generally\nspeaking, we may say that these facts interrupt an interior state of\nthings which was life and to which they put an end. Thus death is\ndefined by life. It is the cessation of the events and of the phenomena\nwhich characterize life. We must, therefore, know what life is to\nunderstand the meaning of death. How wise was Confucius when he said to\nhis disciple, Li-Kou:\u2014\u201cIf we do not know life, how can we know death?\u201d\nAccording to biology there are two kinds of death because there are two\nkinds of life; elementary life and death correspond just as general\nlife and death do, and this is where scientific opinion diverges from\ncommonly received opinion.\n\nWhat cares the man who reasons as most human beings do, about this life\nof the anatomical elements of his body, the existence and the silent\nactivity of which are in no way revealed to him. What does their death\nmatter to him? To him there is but one poignant question, that of being\nseparated or not being separated from the society of his fellows. Death\nis no longer to feel, no longer to think; it is the assurance that one\nwill never feel, one will never think again. Sleep, dreamless sleep,\nis already in our eyes a kind of transient death; but, when we fall\nasleep we are sure of waking again. There is no awaking from the sleep\nof death. But that is not all. Man knows that death, this dreamless\nsleep that knows no waking, will be followed by the dissolution of his\nbody. And what a dissolution will there be for the body, the object\nof his continual care! Remember the description of Cuvier\u2014the flesh\nthat passes from green to blue and from blue to black, the part which\nflows away in putrid venom, the other part which evaporates in foul\nemanations, and finally, the few ashes that remain, the tiny pinch of\nminerals, saline or earthy, which are all that is left of that once\nanimated masterpiece.\n\n_The Popular View._\u2014To the man afraid of death it seems, in the\npresence of so great a catastrophe, that the patient analysis of the\nphysiologist scrupulously noting the succession of phenomena and\nexplaining their sequence is uninteresting. He will only attach the\nslightest importance to knowing that vestiges of vitality remain in\nthis or that part of his body, if they do not re-establish in every\npart the _status quo ante_. He cares not to hear that a certain time\nafter the formal declaration of his death his nails and his hair will\ncontinue to grow, that his muscles will still have the useless faculty\nof contraction, that every organ, every tissue, every element, will\noppose a more or less prolonged resistance to the invasion of death.\n\n_Medical View._\u2014It is, however, these very facts and details, this\nwhy and wherefore, which interest the physiologist. The state of\nmind of the doctor in this respect, again, is different. When, for\ninstance, the doctor declares that such and such a person is dead,\nhe is really making not so much a statement of fact as a prediction.\nHow many elements are still living and will be capable of new birth\nin this corpse that he has before his eyes? That is not what he asks\nhimself, nor is it what we should ask of him. He knows, besides, that\nall these partial survivals will be extinguished and will never find\nthe conditions necessary to reviviscence, and that the organization\nwill never be restored to its primal activity; and this is what he\naffirms. The fear of premature burial which haunts so many imaginations\nis the fear of an error in the prediction. It is to avoid this that\npractical medicine has devoted so much of its attention to the\ndiscovery of a _certain_\u2014and early\u2014sign of death. By this we understand\nthe discovery of a _certain prognostic sign of general death_. We want\na prognostic sign enabling us to assert that the life of the brain is\nnow extinguished and will never be reanimated. And yet there are in\nthat organism many elements which are still alive. Many others even\nmay be born anew if we could give them suitable conditions which they\nno longer meet with in the animal machine now thrown out of gear.\nWhat finer example could we give than the experiment of Kuliabko, the\nRussian physiologist, who kept a man\u2019s heart working and beating for\neighteen hours after the official verification of his death.\n\n\n\n\nCHAPTER II.\n\nTHE PROCESS OF DEATH.\n\n Constitution of organisms.\u2014Partial lives.\u2014Collective life.\u2014The\n r\u00f4le of apparatus.\u2014Death by lesion of the major apparatus.\u2014The\n vital tripod.\u2014Solidarity of the anatomical elements.\u2014Humoral\n solidarity.\u2014Nervous solidarity.\u2014Independence and subordination of the\n anatomical elements.\n\n\n_Partial Lives._ _Collective Life._\u2014With the exception of the\nphysiologist, no one, neither he who is ignorant nor he who is\nintellectual, nor even the doctor, troubles his head about the life\nor the death of the element, although this is the basis, the real\nfoundation, of the activity manifested by the social body and by its\ndifferent organs. The life of the individual, of the animal, depends\non these elementary partial lives just as the existence of the State\ndepends upon that of its citizens. To the physiologist, the organism\nis a federation of cellular elements unified by close association.\nGoethe compared them to a \u201cmultitude\u201d; Kant to a \u201cnation\u201d; and others\nhave likened them to a populous city the anatomical elements of which\nare the citizens, and which possesses an individuality of its own. So\nthat the activity of the federated organism may be discussed in each\nof its parts, and then it is _elementary life_, or in its totality,\nand then it is _general life_. Paracelsus and Bordeu had a glimpse\nof this truth when they considered a life appropriate to each part\n(_vita propria_) and a collective life, the life of the whole (_vita\ncommunis_). In the same way we must distinguish the _elementary death_,\nwhich is the cessation of the vital phenomena in the isolated cell,\nfrom the _general death_, which is the disappearance of the phenomena\nwhich characterised the collectivity, the totality, the federation, the\nnation, the city, the whole in so far as it is a unit.\n\nThese comparisons enable us to understand how general life depends on\nthe partial lives of each anatomical citizen. If all die, the nation,\nthe federation, the total being clearly ceases to exist. This city\nhas an enormous population\u2014there are thirty trillion cellules in the\nbody of man; it is peopled with absolutely sedentary citizens, each\nof which has its fixed place, which it never leaves, and in which\nit lives and dies. It must possess a system of more or less perfect\narrangements to secure the material life of each inhabitant. All have\nanalogous requirements: they feed very much the same; they breathe in\nthe same way; each in fact has its profession, industry, talents, and\naptitudes by which it contributes to social life, and on which, in its\nturn, it depends. But the process of alimentation is the same for all.\nThey must have water, nitrogenous materials and analogous ternaries;\nthe same mineral substances, and the same vital gas, oxygen. It is no\nless necessary that the wastes and the egesta, very much alike in every\nrespect, should be carried off and borne away in discharges arranged so\nas to free the whole system from the inconvenience, the unhealthiness,\nand the danger of these residues.\n\n_Secondary Organization in Organs._\u2014That is why, as we said above, the\nsecondary organizations of the economy exist:\u2014the digestive apparatus\nwhich prepares the food and enables it to pass into the blood, into the\nlymph, and finally into the liquid medium which bathes each cell and\nconstitutes its real medium; the respiratory apparatus which imports\nthe oxygen and exports the gaseous excrement, carbonic acid; the heart\nand the circulatory system which distributes through the system the\ninternal medium, suitably purified and recuperated. The organization\nis dominated by the necessities of cellular life. This is the law of\nthe city, to which Claude Bernard has given the name of the _law of the\nconstitution of organisms_.\n\n_Death by Lesion of the Major Organs. Vital Tripod._\u2014Thus we understand\nwhat life is, and at the same time what is the death of a complex\nliving being. The city perishes if its more or less complicated\nmechanisms which look after its revictualling and its discharge are\nseriously affected at any point. The different groups may survive for\na more or less lengthy period, but progressively deprived of the means\nof food or of discharge, they are finally involved in the general\nruin. If the heart stops, there is a universal famine; if the lungs\nare seriously injured, we are asphyxiated; if the principal organ of\ndischarge, the kidney, ceases to perform its allotted task, there is a\ngeneral poisoning by the used-up and toxic materials retained in the\nblood.\n\nWe understand how the integrity of the major organs,\u2014the heart, the\nlungs, the kidney,\u2014is indispensable to the maintenance of existence. We\nunderstand that their lesion, by a series of successive repercussions,\ninvolves universal death. We always die, said the doctors of old,\nbecause of the failure of one of these three organs, the heart, the\nlungs, or the brain. Life, they said in their inaccurate language,\ndepends upon these as upon three supports. Hence the idea of the _vital\ntripod_. But it is not only this trio of organs which maintain the\norganism; the kidney and the liver are no less important. In different\ndegrees each part exercises its action on the rest. Life is based in\nreality on the immense multitude of living cells associated for the\nformation of the body; on the thirty trillion anatomical elements,\neach part is more or less necessary to all the rest, according as the\nbond of solidarity is drawn more or less closely in the organism under\nconsideration.\n\n_Death and the Brain._\u2014There are indeed more noble elements charged\nwith higher functions than the rest. These are the nervous elements.\nThose of the brain preside over the higher functions of animality,\nsensibility, voluntary movement, and the exercise of the intellect. The\nrest of the nervous system forms an instrument of centralization which\nestablishes the relations of the parts one with the other and secures\ntheir solidarity. When the brain is stricken and its functions cease,\nman has lost the consciousness of his existence. Life seems to have\ndisappeared. We say of a man in this plight that he no longer lives,\nthus confusing general life with the cerebral life which is its highest\nmanifestation. But the man or the animal without a brain lives what may\nbe called a vegetative life. The human anencephalic foetus lives for\nsome time, just as the foetus which is properly formed. Observation\nalways shows that this existence of the other parts of the body cannot\nbe sustained indefinitely in the absence of that of the brain. By a\nseries of impulses due to the solidarity of the grouping of the parts,\nthe injury received by the brain affects by repercussion the other\norgans, and leads in the long run to the arrest of elementary life in\nall the anatomical elements. The death of the whole is then complete.\n\nDoctors have therefore a two-fold reason for saying that the brain\nmay cause death. The death of the brain suppresses the highest\nmanifestation of life, and, in the second place, by a more or less\nremote counter stroke, it suppresses life in all the rest of the system.\n\n_Death is a Process._\u2014Besides, the fact is general. The death of one\npart always involves the death of the rest\u2014_i.e._, universal death. A\nliving organism cannot be at the same time alive and a cemetery. The\ncorpses cannot exist side by side with the living elements. The dead\ncontaminates the living, or in some other way involves it in its ruin.\nDeath is propagated; it is a progressive phenomenon which begins at one\npoint and gradually is extended to the whole. It has a beginning and a\nduration. In other words, the death of a complex organism is a process.\nAnd further, the end of a simple organism, of a protozoan, of a cell,\nis itself a process infinitely more shortened.\n\nThe very perfection of the organism is therefore the cause of its\nfragility. It is the degree of solidarity of the parts one with another\nwhich involves the one set in the catastrophe of the rest, just as in\na delicate piece of mechanism the derangement of a wheel brings nearer\nand nearer the total breakdown. The important parts, the lungs, the\nheart, the brain, suffer no serious alteration without the reflex being\nfelt throughout. But there are also wheels less evident, the integrity\nof which is scarcely less necessary.\n\n_The Solidarity of the Anatomical Elements._\u2014The cause of the mortal\nprocess\u2014_i.e._, of the extension and the propagation of an initial\ndestruction\u2014is therefore to be found in the solidarity of the parts\nof the organism. The closer it is the greater do the chances of\ndestruction become, for the accident which has happened to one will by\nrepercussions affect the others.\n\nNow the solidarity of the parts of the organism may be carried out in\ntwo ways; there is a _humoral solidarity_ and a _nervous solidarity_.\n\n_Humoral Solidarity._\u2014Humoral solidarity is realized by the mixture\nof humours. All the liquids of the organism which have lodged in the\ninterstices of the elements and which soak the tissues, are in contact\nand in relation of exchange one with another, and through the permeable\nwall of the small vessels they are in relation with the blood and the\nlymph.\n\nAll the liquid atmospheres which surround the cells and form their\nambient medium have intercommunication. A change having taken place in\none cellular group, and therefore in the corresponding liquid, modifies\nthe medium of the further or nearer groups, and therefore these groups\nthemselves.\n\n_Nervous Solidarity._\u2014But the real instrument of the solidarity of the\npart is the nervous system. Thanks to it in the living machine the\ncomponent activities of the cellular multitude restrain and control\none another. Nervous solidarity makes of the complex being not a mob\nof cells, but a connected system, an individual in which the parts are\nsubordinated to the whole and the whole to the parts; in which the\nsocial organism has its rights just as the individual has his rights.\nThe whole secret of the vital functional activity of the complex\nbeing is contained in these two factors:\u2014the independence and the\nsubordination of the elementary lives. General life is the harmony of\nthe elementary lives, their symphony.\n\n_Independence and Subordination of the Anatomical Elements._\u2014The\nindependence of the anatomical elements results from the fact that\nthey are the real depositaries of the vital properties, the really\nactive components. On the other hand the subordination of the parts\nto the whole is the very condition of the preservation of form in\nanimals and plants. The architecture which is characteristic of\nthem, the morphological plan which they realize in their evolutive\ndevelopment which they are ever preserving and repairing, form a\nstriking proof of this. This dependence in no way contradicts the\nautonomy of the elements. For when with Claude Bernard and Virchow\nwe study the circumstances we see that the element accommodates\nitself to the organic plan without violence to its nature. It behaves\nin its natural place as it would behave elsewhere, if elsewhere it\nwere to meet around it the same liquid medium which at once is a\nstimulant and a food. This at least is the conclusion we may draw from\nexperiments on transplanting, or on animal and vegetable grafting.\nNeither the neighbouring elements, nor the whole system act on it at\na distance by a kind of mysterious induction, according to the ideas\nof the vitalists, in order to regulate the activity of the element.\nThey contribute solely to the composition of the liquid atmosphere\nwhich bathes it. They intervene in order to provide it with a\ncertain environment whose very characteristic physical and chemical\nconstitution regulates its activity. This constitution may be some day\nimitated by the devices of experiment. When that result is achieved\nthe anatomical element will live in isolation exactly as it lives in\nthe organic association, and the mysterious bond which causes its\nsolidarity with the rest of the economy will become intelligible. In\nfact, we may defer more or less the maturity of this prophecy, but\nthere is no doubt that we are daily nearing its fulfilment.\n\nThe general life of the complex being is therefore the more or less\nperfect synergy, the _ordered process_ of elementary lives. General\ndeath is the destruction of these partial lives. The nervous system,\nthe instrument of this harmony of the parts, represents the social\nbond. It keeps most of the partial elements under its sway, and is\nthus the intermediary of their relations. The closer this dependence,\nthe higher the development of the nervous apparatus, and the better,\nalso, is assured the universal solidarity and therefore the unity of\nthe organism. Cellular federation assumes the characteristic of a\nunique individuality in proportion to the development of this nervous\ncentralization. With an ideal perfect nervous system the correlation\nof the parts would also attain perfection. As Cuvier said: \u201cNone could\nexperience change without a change in the rest.\u201d\n\nBut no animal possesses this extreme solidarity of the parts of the\nliving economy. It is a philosopher\u2019s dream. It is the dream of Kant,\nto whom the perfect organism would be \u201ca teleological system,\u201d a system\nof reciprocal ends and means, a sum total of parts each existing for\nand by the rest, for and by the whole. An organism so completely\nconnected would be unlikely to live. In fact, living organisms show\na little more freedom in the interplay of their parts. Their nervous\napparatus fortunately does not attain this imaginary perfection; their\nunity is not so rigorous. The idea of individuality, of individual\nexistence, is therefore not absolute but relative. There are all\ndegrees of it according to the development of the nervous system. What\nthe man in the street and the doctor himself understand by death is the\nsituation created by the stopping of the general wheels, the brain, the\nheart, and the lungs. If the breath leaves no trace on the glass held\nto the mouth, if the beating of the heart is no longer perceptible by\nthe hand which touches or the ear which listens, if the movement and\nthe reaction of sensitiveness have ceased to be manifest, these signs\nmake us conclude that it is death. But this conclusion, as we have said\nbefore, is a prognostic rather than a judgment of fact. It expresses\nthe belief that the subject will certainly die, and not that it is from\nthis moment dead. To the physiologist the subject is only on the way to\ndie. The process has started. The only real death is when the universal\ndeath of all the elements has been consummated.\n\n\n\n\nCHAPTER III.\n\nPHYSICAL AND CHEMICAL CHARACTERS OF CELLULAR DEATH. NECROBIOSIS.\nGROWING OLD.\n\n Characteristic of elementary life\u2014Changes produced by death in the\n composition and the death of the cell\u2014Schlemm; Loew; Bokorny; Pfl\u00fcger;\n A. Gautier; Duclaux\u2014The processive character of death\u2014Accidental\n death\u2014Necrobiosis\u2014Atrophy\u2014Degeneration\u2014So-called natural\n death\u2014Senescence\u2014Metchnikoff\u2019s theory of senescence\u2014Objections.\n\n\nElementary death is nothing but the suppression in the anatomical\nelements of all the phenomena of vitality.\n\n_Characteristics of Elementary Life._\u2014The characteristic features of\nelementary life have been sufficiently fixed by science. First of\nall, there is _morphological unity_. All the living elements have\nan identical morphological composition. That is to say that life is\nonly accomplished and sustained in all its fulness in organic units\npossessing the anatomical constitution of the cell, with its cytoplasm\nand its nucleus, constituted on the classical type. In the second\nplace, there is _chemical unity_. The constituent matter, the matter of\nwhich the cell is built up, diverges but little from a chemical type\u2014a\nproteid complex, with a hexonic nucleus, and from a physical model\nwhich is an emulsion of granulous, immiscible liquids, of different\nviscosities. The third character consists in the possession of a\n_specific form_ acquired, preserved, and repaired by the element.\nThe fourth character, and perhaps the most essential of all, is _the\nproperty of growth_ or _nutrition_ with its consequence, namely, a\nrelation of exchanges with the external medium, exchanges in which\noxygen plays considerable part. Finally, there is a last property,\nthat of _reproduction_, which in a certain measure is a necessary\nconsequence of the preceding,\u2014_i.e._, of growth.\n\nThese five vital characters of the elements are most in evidence\nin cells living in isolation, in microscopical beings formed of a\nsingle cell, protophytes and protozoa. But we find them also in\nthe associations formed by the cells among one another\u2014_i.e._, in\nordinary plants and animals, multicellular complexes, called for this\nreason metaphytes and metazoa. Free or associated, the anatomical\nelements behave in the same way\u2014feed, grow, breathe, digest in the\nsame manner. As a matter of fact, the grouping of the cells, the\nrelations, proximity and contiguity, which they assume, introduce\nsome variants into the expression of the common phenomena; but these\nslight differences cannot disguise the essential community of the vital\nprocesses.\n\nThe majority of physiologists, following Claude Bernard, admit as\nvalent and convincing the proof that the illustrious experimenter\nfurnished of this unity of the vital processes. There are, however, a\nfew voices crying in the wilderness. M. Le Dantec is one. In his new\ntheory of life he amplifies and exalts the differences which exist\nbetween the elementary life of the proteids and the associated life of\nthe metazoa. In them he can see nothing but contrasts and deviations.\n\nIf this is elementary life, let us ask what is _elementary\ndeath_\u2014_i.e._, the death of the cell. And in this connection let us\nask the questions which we have to examine in the case of animals high\nin organization, and of man himself. What are the characteristics\nof elementary death? When the cell dies, is its death preceded by a\ngrowing old or senescence? What are the preliminary signs and the\nacknowledged symptoms?\n\n_Changes Produced by Death._\u2014The state of death is only truly realized\nwhen the fundamental properties of living matter enumerated above have\nentirely disappeared. We must follow step by step this disappearance in\nall the anatomical elements of the metazoan.\n\nNow the properties of the cell are connected with the physical and\nchemical organization of living matter. For them to disappear entirely,\nthis organization must be destroyed as far as all that is essential in\nit is concerned. We cannot admit with the vitalists that there is any\nmaterial difference between the dead and the living, and that only an\nimmaterial principle which has escaped into the air distinguishes the\ncorpse from the animated being. In fact, the external configuration may\nbe almost preserved, and the corpse may bear the aspect and the forms\nof the preceding state. But this appearance is deceptive. Something in\nreality has changed. The structure, the chemical composition of the\nliving substance, have undergone essential changes. What are these\nchanges?\n\n_Physical Changes._\u2014Certain physiologists have endeavoured to determine\nthem. Klemm, a botanist, pointed out in 1895 the physical changes\nwhich characterize the death of vegetable cells\u2014loss of turgescence,\nfragmentation of the protoplasm, the formation of granules, and the\nappearance of vacuoles.\n\n_Chemical Changes._\u2014O. Loew and Bokorny laid great stress in 1886 and\n1896 on the chemical changes. The living protoplasm according to them\nis an unstable proteid compound. A slight change would detach from the\nalbuminoid molecule a nucleus with the function of aldehyde, and at the\nsame time would transform an amido-group into an amido-group. This\nwould suffice for the transition of the protoplasm from the living to\nthe dead state. This theory is based on the fact that the compounds\nwhich exercise a toxic action on the living cell, without acting\nchemically on the dead albumin, are easily fixed by the aldehydes; and\non the fact that many of them, which attack simultaneously the living\nalbuminoids and the dead albumin, easily combine with the amido-group.\n\nE. Pfl\u00fcger, a celebrated German scientist, has considered living matter\nas an albumin spontaneously decomposable, the essential nucleus of\nwhich is formed by cyanogen. Its active instability would be due to the\npenetration into the molecule of the oxygen which fixes on the carbon\nand separates it from the nitrogen. Armand Gautier has not confirmed\nthis view. Duclaux (1898) has stated that the difference between the\nliving and the dead albumin would be of a stereochemical order.\n\n_Progressive Character of Death. Accidental Death._\u2014We have seen that\nin general the disappearance of the characteristics of vitality is not\ninstantaneous, at least in the natural course of things, in complex\norganisms. It is the end of a more or less rapid process. But death\nis not instantaneous in the isolated anatomical element any more than\nit is in the protozoan or protophyte. We must have recourse to very\nviolent devices of destruction to kill the cell at a blow, to leave\nabsolutely nothing of its organization existing. The protoplasm of\nyeast when violently crushed by B\u00fcchner still possessed the power of\nsecreting soluble ferments. A powerful action, a very high temperature,\nis necessary to obtain the result. _A fortiori_, the difficulty\nincreases in the case of complex organisms, all of whose living\nelements cannot be attacked at the same moment by the destructive\ncause. A mechanical action, capable of destroying at one blow all the\nliving parts of a complex being, of an animal, of a plant, must be of\nalmost inconceivable power. The blow of a Nasmyth hammer would not be\nstrong enough.\n\nThe chemical alteration produced by a very toxic substance distributed\nthroughout the blood, and thus brought into contact with each element,\nwould produce a disorganization which, however rapid it were, could not\nbe called instantaneous. And the same holds good of physical agents.\n\nBut these are not the processes of nature under normal circumstances.\nThey are accidents or devices. We shall leave on one side their\nconsideration and we shall only deal here with the natural processes of\nthe organism.\n\nImagine it placed in a medium appropriate to its needs and following\nout without intervening complications the evolution assigned to it by\nits constitution. Experiment tells us that this natural evolution in\nevery case known to us ends in death. Death supervenes sooner or later.\nFor beings higher in organization, which we can bring into closer\nand closer resemblance to man, we find that they die of disease,\nby accident, or of old age. And as disease is an accident, we may\nnaturally ask if what we call old age is not also a disease.\n\nHowever that may be, the mortal process, being never instantaneous, has\na duration, a beginning, a development, an end\u2014in a word, a history.\nIt constitutes an intermediary phase between perfect life and certain\ndeath.\n\n_Necrobiosis._ _Atrophy._ _Degeneration._\u2014The process according to\nthe circumstances may be shortened or prolonged. When death is the\nresult of violence events are precipitated. The physical and chemical\ntransformations of the living matter constitute a kind of acute\nalteration called by Schultze and Virchow _necrobiosis_. According\nto the pathologists, there are two kinds of _necrobiosis_:\u2014that by\n_destruction_, by _simple atrophy_, which causes the anatomical\nelements to disappear gradually without undergoing appreciable\nmodifications; and _necrobiosis by degeneration_, which transforms the\nprotoplasm into fatty matter into calcareous matter, into granulations\n(fatty degeneration, calcification, granulous degeneration). There is\nno disagreement as to the causes of this necrobiosis. They are always\naccidental; they originate in external circumstances:\u2014the insufficiency\nof the alimentary materials, of water, of oxygen; the presence in the\nmedium of real poisons destroying the organized matter; the violent\nintervention of physical agents, heat, electricity; the reflex on the\ncomposition of the cellular atmosphere of a violent attack on some\nessential organ, the heart, the lungs, the kidneys.\n\n_Senescence._ _Old Age._\u2014In a second category we must place the\nmortal processes, slow in their movement, in which we cannot see the\nintervention of clearly accidental and abnormal disturbing agents.\nDeath appears to be the termination of a breaking-up proceeding by\ninsensible degrees in consequence of the progressive accumulation\nof very small inappreciable perturbations. This slow breaking up\nis adequately expressed by the term\u2014growing old, or senescence.\nThe alterations by which it is betrayed in the cell are especially\n_atrophic_, but they are also accompanied, however, by different\nforms of degeneration. An extremely important question arises on this\nsubject, and that is whether the phenomena of senility have their cause\nin the cell itself, if they are inevitably found in its organization,\nand therefore if old age and death are natural and necessary phenomena.\nOr, on the other hand, should we consider them as due to a progressive\nalteration of the medium, the character of which would be accidental\nalthough frequent or habitual? This, in a word, is the problem which\nhas so often engaged the attention of philosophical biologists. Are old\nage and death natural and inevitable phenomena?\n\nThe recent experiments of Loeb and Calkins, and all similar\nobservations, tend to attribute to the phenomenon of growing old the\ncharacter of a remediable accident. But the remedy has not been found,\nand the animal finally succumbs to these slow transformations of its\nanatomical elements. We then say that it _dies of old age_.\n\n_Metchnikoff\u2019s Theory of Senescence. Objections._\u2014Metchnikoff has\nproposed a theory of the mechanism of this general senescence. The\nelements of the conjunctive tissue, phagocytes, macrophages, which\nexist everywhere around the specialized and higher anatomical elements\nwould destroy and devour them as soon as their vitality diminishes,\nand would take their place. In the brain, for example, it would be the\nphagocytes which, attacking the nervous cellules, would disorganize the\nhigher elements, incapable of defending themselves. This substitution\nof the conjunctive tissue, which only possesses vegetative properties\nof a low order, for the nervous tissues, which possesses very high\nvegetative properties, results in an evident breaking-up. The gross\nelement of violent and energetic vitality stifles the refined and\nhigher element.\n\nThis expulsion is a very real fact. It constitutes what is called\nsenile sclerosis. But the active _r\u00f4le_ attributed to it by Metchnikoff\nin the process of degeneration is not so certain. An expert observer\nin the microscopic study of the nervous system, M. Marinesco, does not\naccept this interpretation as far as the senescence of the elements of\nthe brain is concerned. Diminution of the cell, the decrease in the\nnumber of its stainable granulations, chromatolysis, the formation of\ninert, pigmented substances\u2014all these phenomena which characterize the\nbreaking-up of the cerebral cells would be accomplished, according to\nthis observer, without the intervention of the conjunctive elements,\nthe phagocytes.\n\nThe characteristic of extensive and progressive process presented\nby death necessitates in a complex organism, which is a prey to it,\nthe existence side by side of living and dead cells. Similarly, in\nthe organism which is growing old, there are young elements and\nelements of every age side by side with senile elements. As long as\nthe disorganization of the last has not gone too far, they may be\nrejuvenated. All we have to do is to restore to them an appropriate\nambient medium. The whole question is one of knowing and being able\nto realize, for this or that part which we wish to reanimate and to\nrejuvenate, the very special or very delicate conditions that this\nmedium must fulfil. As we have said, success is attained in this\nrespect as far as the heart is concerned, and this is why we are able\nto reanimate and to revive the heart of a dead man. It is hoped that\nideas along these lines will extend with the progress of physiology.\n\nAfter this sketch of the conditions and of the varieties of cellular\ndeath we must return to the essential problem which is engaging the\ncuriosity of biologists and philosophers. Is death unavoidable,\ninevitable? Is it the necessary consequence of life itself, the\ninevitable issue, the inevitable end?\n\nThere are two ways of endeavouring to solve this question of the\ninevitability of death. The first is to examine popular observation,\npractised, so to speak, unintelligently and without special\nprecautions. The second is to analyze everything we know relative to\nthe conditions of elementary life.\n\n\n\n\nCHAPTER IV.\n\nTHE APPARENT PERENNITY OF COMPLEX INDIVIDUALS.\n\n Millenary trees\u2014Plants with a definite rhizome\u2014Vegetables\n reproduced by cuttings\u2014Animal colonies\u2014Destruction due to extrinsic\n causes\u2014Difficulty of interpretation.\n\n\nPopular opinion teaches us that living beings have only a transient\nexistence, and as a poet has said: \u201cLife is but a flash between two\ndark nights.\u201d But, on the other hand, simple observation shows us, or\nappears to show us, beings whose duration of existence is far longer,\nand practically illimitable.\n\n_Millenary Trees._\u2014We know of trees of venerable antiquity. Among these\npatriarchs of the vegetable world there is a chestnut tree on Mount\nEtna which is ten centuries old, and an ivy in Scotland which is said\nto be thirty centuries old. Trees of 5000 years old are not absolutely\nunknown. We may mention among those of that age the famous dragon\ntree[21] at Orotava, in the island of Teneriffe. Two other examples are\nknown in California\u2014the pseudo-cedar, or _Tascodium_, at Sacramento,\nand a _Sequo\u00efa gigantea_. We know that the olive tree may live 700\nyears. There are cedars 800 years old and oaks of the age of 1,500\nyears.\n\n [21] Lately destroyed in a storm. [Tr.]\n\n_Plants with a Rhizome._\u2014Vegetable species of almost unlimited\nduration of life are known to botanists. Such, for instance, are plants\nwith a definite rhizome, such as colchicum. Autumnal colchicum has a\nsubterranean root, the bulb of which pushes out every year fresh axes\nfor a new bloom; and as each of these new axes stretches out an almost\nconstant length, a botanist once set himself the singular problem of\ndiscovering how long it would take such a foot, if suitably directed,\nto travel round the world.\n\n_Vegetables Reproduced by Cuttings._\u2014Vegetables reproduced by slips\nfurnish another example of living beings of indefinite duration. The\nweeping willows which adorn the banks of sheets of water in the parks\nand gardens throughout the whole of Europe have sprung, directly or\nindirectly, from slips of the first _Salix Babylonica_ introduced to\nthe West. May it not be said that they are the permanent fragments of\nthat one and the same willow?\n\n_Animal Colonies._\u2014These examples, as well as those furnished to\nzoologists by the consideration of the polypi which have produced by\ntheir slow growth the reefs, or _atolls_, of the Polynesian seas,\ndo not, however, prove the perennity of living beings. The argument\nis valueless, for it is founded upon a confusion. It turns on the\ndifficulty that biologists experience in defining the individual. The\noak and the polypus are not simple individuals, but associations of\nindividuals, or, to use Hegel\u2019s expression, the nations of which we see\nthe successive generations. We give to this succession of generations\na unique existence, and our reasoning comes to this, that we confer on\neach present citizen of this social body the antiquity which belongs to\nthe whole.\n\n_Destruction of the Social Individual due to Extrinsic Causes._\u2014As\nfor the destruction, the death of this social individual, of this\nhundred-year-old tree, it seems indeed that there is no ground for\nconsidering it a natural necessity. We find the sufficient reason of\nits usual end in the repercussion on the individual of external and\ncontingent circumstances. The cause of the death of a tree, of an oak\nmany centuries old, is to be found in the ambient conditions, and not\nin some internal condition. Cold and heat, damp and dryness, the weight\nof the snow, the mechanical action of the rain, of hail, of winds\nunchained, of lightning; the ravages of insects and parasites\u2014these are\nwhat really work its ruin. And further, the new branches, appearing\nevery year and increasing the load the trunk has to bear, increase the\npressure of the parts, and make more difficult the motion of the sap.\nBut for these obstacles, external, so to speak, to the vegetable being\nitself, it would continue indefinitely to bloom, to fructify, and as\neach spring returned to show fresh buds.\n\n_Difficulty of Interpretation._\u2014In this as in all other examples we\nmust know the nature of the beings that we see lasting on and braving\nthe centuries. Is it the individual? Is it the species? Is it a living\nbeing, properly so called, having its unity and its individuality,\nor is it a series of generations succeeding one another in time and\nextending in space? In a word, the question is one of knowing if we\nhave to do with a real tree or with a genealogical tree. We are just\nas uncertain when we deal with animals. What is the being that lasts\non\u2014a series of generations or an individual? This doubt forbids us to\ndraw any conclusion from the observation of complex beings. We must\ntherefore return from them to the _elementary being_; and we must\nexamine it from the point of view of perennity or of vital decay. Let\nus then ask the questions that we have already examined with reference\nto animals high in organization and to man himself. Is the death of the\ncell an inevitable characteristic? Are there any cells, protophytes,\nprotozoa, which are immortal?\n\n\n\n\nCHAPTER V.\n\nTHE IMMORTALITY OF THE PROTOZOA.\n\n Impossibility of life without evolution\u2014Law of increase and\n division\u2014Immortality of the protozoa\u2014Death, a phenomenon of adaptation\n which has appeared in the course of the ages\u2014The infusoria\u2014The\n death of the infusoria\u2014Two kinds of reproduction\u2014The caryogamic\n rejuvenescence of Maupas\u2014Calkins on rejuvenescence\u2014Causes of\n senescence\u2014Impossibility of life without evolution.\n\n\nWe take into account, _a priori_, the conditions that must be fulfilled\nby the monocellular being in order to escape the inevitability of\nevolution, of the succession of ages, of old age, and of death. It must\nbe able indefinitely to maintain itself in a normal r\u00e9gime, without\nchanging, without increasing, maintaining its constant morphological\nand chemical composition, in an environment vast enough for it to\nbe unaltered by the borrowings or the spendings resulting from its\nnutrition\u2014_i.e._, it must remain constant in the presence of the\nconstant being. We might conceive of a nutrition perfect enough, of\nexchanges exact enough, and regular enough, for the state of things to\nbe indefinitely maintained. This would be absolute permanence realized\nin the vital mobility.\n\n_The Law of Growth and Division._\u2014This model of a perfect and\ninvariable machine does not exist in nature. Life is incompatible with\nthe absolute permanence of the dimensions and the forms of the living\norganism.\n\nIn a word, it is a rigorous law of living nature that the cell can\nneither live indefinitely without growth, nor grow indefinitely without\ndivision.\n\nWhy is this so? Why is there this impossibility of a regular r\u00e9gime in\nwhich the cell would be maintained in magnitude without diminution or\nincrease? Why has nutrition as a necessary consequence the growth of\nthe element? This is what we do not positively know.\n\nThings are so. It is an irreducible fact, peculiar to the protoplasm, a\ncharacteristic of the living matter of the cell. It is the fundamental\nbasis of the property of generation. That is all we can say about it.\nReal living beings have therefore inevitably an evolution. They are not\nunchangeable. In its simple form this evolution consists in the fact\nthat the cell grows, divides, and diminishes by this division, begins\nthe upward march which ends in a new division. And so on.\n\n_Immortality of the Protozoa._\u2014It may happen, and it does happen\nin fact, that this series of acts is repeated indefinitely at any\nrate unless an accidental cause should interrupt it. The animal thus\ndescribes an indefinite curve, constituted by a series of indentations,\nthe highest point of which corresponds to the maximum of size, and the\nlowest point to the diminution which succeeds the division. This state\nof things has no inevitable end if the medium does not change. The\nbeing is immortal.\n\nIn fact, the compound beings of a single cell, protophytes and\nprotozoa, the algae and the unicellular mushrooms, at the minimum stage\nof differentiation, escape the necessity of death. They have not, as\nWeismann remarks, the real immortality of the gods of mythology, who\nwere invulnerable. On the contrary, they are infinitely vulnerable,\nfragile, and perishable; myriads die every moment. But their death is\nnot inevitable. They succumb to accidents, never to old age.\n\nImagine one of these beings placed in a culture medium favourable to\nthe full exercise of its activities, and, moreover, wide enough in\nits extent to be unaffected by the infinitely small quantities of\nmaterial which the animal may take from it or expel into it. Suppose,\nfor example, it is an infusorian in an ocean. In this invariable medium\nthe being lives, increases, and grows continually. When it has reached\nthe limits of a size fixed by its specific law, it divides into two\nparts, which are indistinguishable the one from the other. It leaves\none of its halves to colonize in its neighbourhood, and it begins its\nevolution as before. There is no reason why the fact should not be\nrepeated indefinitely, since nothing is changed, either in the medium\nor in the animal.\n\nTo sum up. The phenomena which take place in the cell of the protozoan\ndo not behave as a cause of check. The medium allows the organism\nto revictual and to discharge itself in such a way and with such\nperfection that the animal is always living in a regular r\u00e9gime, and,\nwith the exception of its growth and later on of its division, there is\nnothing changed in it.\n\n_Death a Phenomenon of Adaptation\u2014It appeared in the Course of the\nAges._\u2014This immortality belongs in principle to all the protista which\nare reproduced by simple and equal division. If it be remarked that\nthese rudimentary organisms endowed with perennity are the first living\nforms which have shown themselves on the surface of the globe, and\nthat they have no doubt preceded many others\u2014the multicellular, for\ninstance, which are liable, on the contrary, to decay\u2014the conclusion\nis obvious:\u2014Life has long existed without death. Death has been a\nphenomenon of adaptation which has appeared in the course of the ages\nin consequence of the evolution of species.\n\n_The Death of Infusoria._\u2014We may ask ourselves at what moment in the\nhistory of the globe, at what period of the evolution of its fauna,\nthis novelty, death, made its appearance. The celebrated experiments of\nMaupas on the senescence of the infusoria seem to authorize us to give\na precise answer to this question. By means of these experiments we are\nled to believe that death must have appeared at the same time as sexual\nreproduction. Death became possible when this process of generation was\nestablished, not in all its plenitude, but in its humblest beginnings,\nunder the rudimentary forms of unequal division and of conjugation.\nThis happened when the infusoria began to people the waters.\n\n_The Two Modes of Multiplication._\u2014Infusoria are, in fact, capable of\nmultiplication by simple division. It is true to say that in addition\nto this resource, the only one which interests us here, because it\nis the only one which confers immortality, they possess another.\nThey present and exercise under certain circumstances a second mode\nof reproduction, caryogamic conjugation. It is a rather complicated\nprocess in its detail, but it is definitively summed up as the\ntemporary pairing of two individuals, which are otherwise very much\nalike, and which cannot be distinguished as male and female. They\nbecome closely united on one of their faces; they reciprocally exchange\na semi-nucleus which passes into the conjoint individual; and then\nthey separate. But infusoria can be prevented from this conjunction by\nregularly isolating them immediately after their birth. Then they grow,\nand are constrained after a lapse of time to divide according to the\nfirst method.\n\nMaupas has shown that the infusoria could not accommodate themselves\nto this r\u00e9gime indefinitely; they could not go on dividing for ever.\nAfter a certain number of divisions they show signs of degeneration\nand of evident decay. The size diminishes, the nuclear organs become\natrophied, all the activities fail, and the infusorian perishes.\nIt succumbs to this kind of senile atrophy unless it is given an\nopportunity of conjugation with another infusorian in the same plight.\nIn this act it then derives new strength, it grows larger, attains its\nproper size, and builds up its organs once more. Conjugation gives it\nlife, youth, and immortality.\n\n_Alimentary Rejuvenescence._\u2014Recent observations due to Mr. G. N.\nCalkins, an American biologist, and confirmed by other investigators,\nhave shown that this method of rejuvenescence is not the only one,\nand is not even the most efficacious. Conjugation has no mysterious,\nspecific virtue. The infusoria need not be married in order to be\nrejuvenated. It is sufficient to improve their food. In the case of\nthe \u201ctailed\u201d paramecium we may substitute beef broth and phosphates\nfor conjugation. Calkins observed 665 consecutive generations without\nblemish, without exhaustion, and without any sign of old age. Plenty of\nfood and simple drugs have successfully resisted senility and the train\nof atrophic degenerations which it involves.\n\n_Causes of Senescence._\u2014As for the causes of senescence which have\nbeen remedied with such success, they are not exactly known. Calkins\nthinks that senescence results from the progressive losses to the\norganism of some substance essential to life. Conjugation or intensive\nalimentation would act by building up again this necessary compound.\nG. Loisel believes on the contrary that it is a matter of the\nprogressive accumulation of toxic products due to a kind of alimentary\nauto-intoxication.\n\n\n\n\nCHAPTER VI.\n\nLETHALITY OF THE METAZOA AND OF DIFFERENTIATED CELLS.\n\n Evolution and death of metazoa.\u2014Possible rejuvenescence of the\n differentiated cells by the conditions of the medium.\u2014Conditions of\n the medium for immortal cells.\u2014The immortal elements of metazoa.\u2014The\n element in accidental and remediable death.\u2014Somatic cells and sexual\n cells.\n\n\n_Evolution and Death of Metazoa._\u2014We have seen that the infusoria\nare no longer animals in which material exchanges take place with\nsufficient perfection, and in which cellular division, the consequence\nof growth, is produced with sufficient precision and equality for\nlife to be carried on indefinitely in a perfect equilibrium in the\nappropriate medium without alteration or check. _A fortiori_ we no\nlonger find the perfect regularity of nutritive exchange in the classes\nabove them. In a word, starting from this inferior group, there are\nno animated beings in the state of existence which Le Dantec calls\n\u201ccondition I\u00ba of manifested life?\u201d Living matter, instead of being\ncontinually kept identical in conditions of identical media, is\nmodified in the course of existence. It becomes dependent on time. It\ndescribes a declining trajectory; it experiences evolution, decay,\nand death. Thus the fundamental condition of invariable youth and of\nimmortality fails in all metazoa. The vital wastes accumulate in all\nthrough the insufficiency or the imperfection of nutritive absorption\nor of excretion. Life decays; the organism progressively alters, and\nthus is constituted that state of decrepitude by atrophy or chemical\nmodification which we call senescence, and which ends in death. To sum\nup, old age and death may be attributed to cellular differentiation.\n\n_Possible Alimentary Rejuvenescence of the Differentiated\nCells\u2014Conditions of Medium._\u2014We must add, however\u2014as the teaching\nof experiments in general and in particular as the teaching of the\nexperiments of Loeb and of Calkins\u2014that a slight change of the\nenvironment, made at the right time, is capable of re-establishing\nequilibrium and of completely rejuvenating the infusorian. Senescence\nhas not in this case a definitive any more than an intrinsic character;\na modification in the composition of the alimentary medium will\nsuccessfully resist it. If we are allowed to generalize this result, it\nmay be said that senescence, the declining trajectory, the evolution\nstep by step down to death, are not for the cells considered in\nisolation an inevitable and essentially inherent in the organism, and\na rigorous consequence of life itself. They preserve an accidental\ncharacter. In senescence and death there is no really natural, internal\ncause, inexorable, and irremediable, as was claimed in the past by J.\nM\u00fcller, and more recently by Cohnheim in Germany and Sedgwick Minot in\nAmerica.\n\n_Conditions of the Medium for Immortal Cells._\u2014As for the cells which\nare less differentiated, the protophytes and the protozoa situated\none degree lower in the scale than the infusoria, we must admit the\npossibility of that perfect and continuous equilibrium which would\nsave them from senile decrepitude. And it is quite understood that\nthis privilege remains subordinated to the perfect constancy of the\nappropriate medium. If the latter changes, the equilibrium is broken,\nthe small insensible perturbations of nutrition accumulate, vital\nactivity decays, and in sole consequence of the imperfection of the\nextrinsic conditions or of the medium, the living being finds itself\nonce more dragged down to decay and to death.\n\n_Immortal Elements of the Metazoa._\u2014All the preceding facts and\nconsiderations refer to isolated cells, to monocellular beings.\nBut, and this is what makes these truths so interesting, they may\nbe extended to all cells grouped in collectivity\u2014i.e., to all the\nanimals and living beings that we know. In the complicated edifice\nof the organism, the anatomical elements, at any rate the least\ndifferentiated, would have a continual brevet of immortality. Generally\nspeaking, this would be the case for the egg, for the sexual elements,\nand perhaps, too, for the white globules of the blood, the leucocytes.\nAnd, further, around each of these elements must be realized the\ninvariably perfect medium which is the necessary condition. This does\nnot take place.\n\n_Elements in Accidental and Remediable Death._\u2014As for the other\nelements, they are like the infusoria, but without the resource of\nconjugation. The ambient medium becomes exhausted and intoxicated\naround each cell, in consequence of the accidents which happen to the\nother cells. Each therefore undergoes progressive decay, and finally\nthey perish\u2014the decay and destruction being perhaps in principle\naccidental, but, in fact, they are the rule.\n\nThe different anatomical elements of the organism are more or less\nsensitive to those perturbations which cause senescence, necrobiosis,\nand death. There are some more fragile and more exposed. Some are more\nresisting, and finally, there are some which are really immortal. We\nhave just said that the sexual cell, the ovum, is one. It follows that\nthe metazoan, man for instance, cannot entirely die. Let us consider\none of these beings. Its ancestors, so to speak, have not entirely\ndisappeared; each has left the fertile egg, the surviving element from\nwhich has issued the being of which we speak; and when it in its turn\nhas developed, part of that ovum has been placed in reserve for a new\ngeneration. The death of the elements is not therefore universal. The\nmetazoan is divided from the beginning into two parts. On the one\nhand are the cells destined to form the body, _somatic_ cells. They\nwill die. On the other hand are the _reproductive_, or _germinal_, or\n_sexual_ cells, capable of living indefinitely.\n\n_Somatic and Sexual Cells._\u2014In this sense we may say with Weismann\nthat there are two things in the animal and in man\u2014the one mortal,\nthe _soma_ the body, the other immortal, the _germen_. These germinal\ncells, as in the case of the protozoa we mentioned above, possess a\nconditional immortality. They are imperishable, but on the contrary,\nare fragile and vulnerable. Millions of ova are destroyed and are\ndisappearing every moment. They may die by accident, but never of old\nage.\n\nWe now understand that if the protistae are immortal, it is because\nthese living beings, reduced to a single cell, accumulate in it the\ncompound characters of the somatic cell and germinal cell, and enjoy\nthe privilege which is attached to the latter.\n\n\n\n\nCHAPTER VII.\n\nMAN. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH.\n\n The miseries of humanity: 1. Disease; 2. Old age.\u2014Old age considered\n as a chronic disease.\u2014Its occasional cause.\u20143. The disharmonies of\n human nature; 4. The instinct of life and the instinct of death.\n\n\nMan\u2019s unhappy plight is the constant theme of philosophies and\nreligions. Without referring to its moral basis, it has a physical\nbasis due to four causes\u2014the physical imperfection or disharmony of\nnature, disease, old age, and death\u2014or rather of three, for what we\ncall old age is perhaps a simple disease. These are the great sorrows\nof man, the sources of all his woes. Disease attacks him, old age\nawaits him, and death must tear him from all the ties which he has\nformed. All his pleasures are poisoned by the certain knowledge that\nthey last but for a moment, that they are as precarious as his health,\nhis youth, and his life itself.\n\n\n \u00a7 1. DISEASE.\n\n\nDisease, frequent, constant, and inevitable as it is, is, however,\nnothing but a fact outside the natural order. Its character is clearly\naccidental, and it interrupts the normal cycle of evolution. Medical\nobservation teaches us, on the other hand, that the health of the body\nreacts on that of the mind; and therefore man as a whole, moral and\nphysical, is affected by disease. Bacon described a diseased body as a\njailer to the soul, and the healthy body as a host. Pascal recognized\nin diseases a principle of error. \u201cThey spoil our judgment and our\nsenses.\u201d\n\nI am not expressing a chimerical hope when I predict that science will\nconquer disease. Medicine has at last issued from the contemplative\nattitude of so many centuries; it has engaged in the struggle, and\nsigns of victory are already appearing. Disease is no longer the\nmysterious power which it was impossible to escape. Pasteur gave to it\na body. The microbe can be caught. In the words of Schopenhauer, an\nalteration of the atmosphere so slight that it is impossible to detect\nit by chemical analysis may bring on cholera, yellow fever, the black\nplague, diseases which carry off thousands of men; and a slightly\ngreater alteration might endanger all life. The at once mysterious\nand terrifying spectacle of the cholera at Berlin in 1831 had such\nan effect on the philosopher that he fled in terror to Frankfort. It\nhas been said that this was the origin of his pessimism, and that\nbut for this he would have continued to teach idealistic philosophy\nin some Prussian university. L. Hartmann, another celebrated leader\nof contemporary pessimism, has also said that disease will always be\nbeyond the resources of medicine. Facts have given the lie to these\nsombre prognostics. The microbic origin of most infectious diseases has\nbeen recognized. The discovery of attenuated poisons and serums has\ndiminished their gravity. An exact knowledge of methods of contagion\nhas enabled us to erect against them impregnable barriers. Cholera,\nyellow fever, the plague knock in vain at our doors. Diphtheria,\ndreaded by every mother, has partially lost its deadly character.\nPuerperal fever and blindness of the new-born child are tending to\ndisappear. Legend tells us that Buddha in his youth, frightened at\nthe sight of a sick man, expressed in his father\u2019s presence the wish\nto be always in perfect health and sheltered from disease. The King\nanswered: \u201cMy son! you are asking the impossible.\u201d But it is towards\nthe realization of this impossibility that we are on our way. Science\nis repelling the attacks of disease.\n\n\n \u00a7 2. OLD AGE.\n\n\nOld age is another sorrow of humanity. The stage of existence in\nwhich the strength grows less and never grows greater, and in which\na thousand infirmities appear, is not, however, a stage universal in\nanimals. Most of them die without our perceiving in them any apparent\nsigns of senile weakness. On the other hand, some vegetables exhibit\nthese signs. Some trees are old; but it is in birds and mammals that\nthis decay, with the train of evils which accompanies it, becomes a\nvery marked phase of existence. In man to debility is added a bodily\nshrinkage, grey hairs, withered skin, and the wearing out and loss of\nteeth. The exhausted and atrophied organism offers a favourable field\nto all intercurrent diseases and to every cause of destruction. It is\nthis discrepitude which makes old age so hateful. All desire to be old,\nsaid Cicero; and when they are old, they say that old age has come\nquicker than they expected. La Bruy\u00e8re expresses it in an apothegm,\n\u201cWe want to grow old, and we fear old age.\u201d One would like longevity\nwithout old age.\n\nBut can life be prolonged without senility diminishing its value?\nMetchnikoff thinks it can. He more or less clearly catches a glimpse\nof a normal evolution of existence which would make it longer and\nnevertheless exempt from senile decay.\n\nIt is remarkable that we have so few scientific data on the old age of\nman, and we have still fewer on that of animals. The biologist knows\nno more than the layman. The old age of the dog is betrayed by its\ngait. Its coat loses its lustre, just as in disease. The hair whitens\naround the forehead and the muzzle. The teeth grow blunt and drop out.\nThe character loses its gaiety and becomes gloomy; the animal becomes\nindifferent. He ceases to bark, and often becomes blind and deaf.\n\nIt is admitted that senile degeneration is due to an alteration\naffecting most of the tissues. The cells, the special anatomical\nelements of the liver, the kidney, and the brain are reduced by atrophy\nand degeneration. At the same time, the conjunctive woof which serves\nthem as a support develops, on the contrary, at the expense in a\nmeasure of the higher elements. For this reason the tissues harden.\nWe know that the flesh of old animals is tough. We know in pathology\nthat this is happening to the tissues. It is due to growth, to injury\nto the active and important elements, to the elements of support of\nthe organs. They form a tissue sometimes called packed tissue, to\nshow its secondary r\u00f4le with reference to the elements which are\ndeposited in it. This kind of degeneration of the organs is known as\nsclerosis. It constitutes the characteristic lesion of a certain number\nof chronic diseases; and these diseases are serious, for the stifling\nof the characteristic elements by the less important elements of the\nconjunctive or packed tissue results in the more or less complete\nreduction or suppression of the function.\n\nThe blood vessels also undergo this transformation, and what we\nmay call universal trouble and danger ensue. This sclerosis of the\narteries, this arterio-sclerosis, not only deprives the walls of the\nblood vessels of the suppleness and elasticity which are necessary for\nthe proper irrigation of the organs, but it makes them more fragile.\nThus it becomes a cause of hemorrhage, which is a very serious matter\nas far as the brain and lungs are concerned.\n\nIt is remarkable that the alteration of the tissues during old age\nshould be exactly similar to this. This is inferred from the few\nresearches that have been made on the subject\u2014from those of Demange in\n1886, of Merkel in 1891, and finally from the researches of Metchnikoff\nhimself. It is a generalized sclerosis. As its consequence we have\nthe lowering of the proper activity of the organs and the danger of\ncerebral hemorrhage created by arterio-sclerosis. The transformations\nof the tissues in old men are therefore summed up in the atrophy of the\nimportant and specific elements of the tissues, and their replacement\nby the hypertrophied conjunctive tissue. This sclerosis is comparable\nto that of chronic diseases; it is a pathological condition. Thus old\nage, as we understand it, is a chronic disease and not a normal phase\nof the vital cycle.\n\nOn the other hand, if we ask ourselves what is the origin of the\nscleroses which engender chronic diseases, we find that they are due\nto the action of various poisons, among which syphilitic poison and\nthe immoderate use of alcohol take the first place. These are also the\nusual causes of senile degeneration. But there must be some other,\nsome very general cause to explain the universality of the process of\nsenescence. Metchnikoff thinks that he has found this cause in the\nmicrobes which swarm in man\u2019s digestive tube, particularly in the\nlarge intestine. Their number is enormous. Strassburger has given\nan approximate calculation, but words fail to express it. We have\nto imagine a figure followed by fifteen zeros. This microbic flora\nis composed of \u201cbacilli\u201d and of \u201ccocci,\u201d and comprises a third of\nthe rejected matter. It produces slow poisons, which, being at once\nreabsorbed, pass into the blood and provoke the constant irritation\nfrom which results arterio-sclerosis and the universal sclerosis of old\nage. Instead of enjoying a healthy and normal old age, in which the\nfaculties of ripening years are preserved, we drag out a diminished\nlife, a kind of chronic disease, which is ordinary old age. This is\ndue, according to Metchnikoff, to the parasitism and the symbiosis\nof microbic flora, lodged in a part of the economy in which it finds\nall the conditions favourable to its prolific expansion. Such is the\nspecious theory, held to the verge of intrepidity, by which this\ninvestigator explains the misery of our old age, and which inspires him\nwith the idea of a remedy. For his observations conclude with a r\u00e9gime,\na series of prescriptions by which the author fancies that life may be\nlengthened and the evils of old age swept from our path. The dangerous\nflora must be transformed into a cultivated and selected flora.\nAlthough the organ in question may be of doubtful utility, and although\nits existence, the legacy of atavic heredity, must be considered as\na disharmony of human nature, Metchnikoff does not go so far as to\npropose that it should be cut away, and that we should call in surgery\nto assist in making mankind perfect! But the rational means he proposes\nwill be endorsed by the most judicious students of hygiene; and their\neffect, if it is not as wonderful as one hopes for, cannot fail to\nameliorate the conditions of old age and make it more vigorous.\n\n\n \u00a7 3. DISHARMONIES IN HUMAN NATURE.\n\n\nAnother misery in the condition of man is due to the dissidencies\nof his nature\u2014that is to say, to his physical imperfections and the\ndiscordancies which exist between the physiological functions and the\ninstincts which should regulate them.\n\nThis discordance reigns throughout the physical organism. The body of\nman is not the perfect masterpiece it was once supposed to be. It is\nencumbered with annoying inutilities, with rudimentary organs that have\nneither r\u00f4le nor function, unfinished sketches which nature has left\nin the different parts of his body. Such are the lachrymal caruncle, a\nvestige of the third eyebrow in mammals; the extrinsic muscles of the\near; the pineal gland of the brain, which is only the rudiment of an\nancestral organ; the third eye, or the Cyclopean eye of the saurians.\nThe list is interminable. Wiedersheim has counted in man 107 of these\nabortive hereditary organs, the useless vestiges of organs useful\nto our remote animal ancestors, atrophied in the course of ages in\nconsequence of modifications that have taken place in the external\nmedium.\n\nThese rudimentary organs are not only useless; they are often\npositively harmful.\n\nBut the most serious discordance is that which exists between the\nphysiological functions and the instincts which regulate them. In a\nwell-regulated organism slowly developed by adaptation the instincts\nand the organs alike should be in relation with the functions. All\nreally natural acts are solicited by an instinct, the satisfaction\nof which is at once a need and a pleasure. The maternal instinct is\nawakened at the proper moment in animals, and it disappears as soon as\nthe offspring requires no more assistance. A craving for milk is shown\nin all newborn children, and often disappears at an early age.\n\nNature has endowed man as well as the other animals with peculiar\ninstincts, destined to preside over the different functions and to\nensure their accomplishment. And, at the same time, it has enabled him\nin a measure to deceive those instincts and to satisfy them by other\nmeans than the execution of the physiological acts with a view to which\nthey exist. Love and the instinct of reproduction exist in man before\nthe age of puberty. Canova felt the spur of love at the age of five.\nDante was in love with Beatrice at nine; and Byron, then scarcely\nseven, was already in love with Maria Duff. On the other hand, puberty\nhas no necessary relation to the general maturity of the organism.\n\nThe family instinct is subject to the same aberrations. Man limits\nthe number of his children. The Turks of to-day follow the ancient\nGreeks in the practice of abortion. Plato approved of the custom, and\nAristotle sanctioned its general prevalence. In the province of Canton\nthe Chinese of the agricultural classes kill two-thirds of their girl\nchildren, and the same is done at Tahiti. All these customs co-exist\nwith the perfect love and tender care of the living children.\n\nBecause of these different discordancies the physical life of man is\ninsufficiently regulated by nature. Neither the physiological instinct,\nnor the family instinct, nor the social instinct is, in general,\nsufficiently imperative and precise. Hence, since the internal impulse\nhas not sufficient power, the necessity arises for a rule of conduct\nexercising its influence from without. Philosophies, religions, and\nlegislation have provided for this. They have regulated man\u2019s hygiene\nand the carrying out of his different physiological functions. Their\ncontrol has, moreover, had its hygienic side. The scientific hygiene of\nto-day has inherited their r\u00f4le.\n\nThe idea of the fundamental perversity of human nature is born of our\ncognizance of its discordancies, unduly amplified and exaggerated. Soul\nand body have been considered as distinctly discordant and hostile\nelements. The body, the shroud of the soul, the temporary host, the\nprison, the present source of miseries, has been subjected to every\nkind of mortification. Asceticism has treated the body and all the\ninnate instincts as our mortal foes.\n\nThis suspicion, this depreciation of human nature was the great\nerror of the mystics. This view was as fatal as the inverse view\nof pagan antiquity. The model of the perfect life according to\nGreek philosophy is a life in conformity with nature. To aim at the\nharmonious development of man was the precept of the ancient Academy,\nformulated by Plato. The Stoics and the Epicureans had adopted the\nsame principle. Physical nature is considered as good. It gives us\nthe type, the rule, and the measure. The moral rule itself is exactly\nappropriate to the physical nature. We may say that pagan morality was\nhygiene, the hygiene of the soul and the body alike; the _mens sana in\ncorpore sano_ gave individual and social direction. The Rationalists,\nthe philosophers of the eighteenth century, such as Baron d\u2019Holbach\nand later W. Von Humboldt, Darwin, and Herbert Spencer, have adopted\nanalogous views. If these views have been contested, it is because of\nthe imperfections or aberrations of the natural instincts of man. Also,\nif we wish to base individual family or social morality on the natural\ninstincts of man, it must be specified that these instincts are to be\nregularized. We must necessarily appeal from the imperfect instincts of\nthe present to the perfected instincts of the future. Their perfection,\nmoreover, will only be a more exact approximation to the real nature of\nman, and he, having avoided by the aid of science the accidents which\ncause disease and senile decrepitude, will enjoy a healthy youth and an\nideal old age.\n\nThe reason of the discrepancies between instinct and function in man is\ngiven by the natural history of his development. We know that man has\nwithin him original sin\u2014his long atavism. He has sprung, according to\nthe transformists, from a simian stock. He is a cousin, the successful\nrelation, of a type of antinomorphic monkeys, the chimpanzees. He\nhas \u201carrived,\u201d they have remained undeveloped. Probably he had a\ncommon ancestor with them, some dryopithecan of an extinct species.\nFrom that type sprang a new type already on the way to progress, the\n_Pithecanthropus erectus_. Finally, the anthropoid ancestor became\none fine day the father of a scion, clearly superior to himself, a\nmiraculously gifted being, man. Here, then, is no sign of the slow\nevolution and gradual progress, which is the doctrine held at present\nby Transformists. The Dutch botanist De Vries has shown us, in fact,\nthat nature does leap: _natura facit saltus_. There would thus be\ncrises, as it were, in the life of species. At certain critical epochs\nconsiderable differences of a specific value appear in their offspring.\nIt is at one of these critical periods in the simian life that man\nhas appeared as the phenomenal child of an anthropoid. He was born\nwith a brain and an intellect superior to those of his humble parents;\nand on the other hand, he has inherited from them an organization\nwhich is only inadequately adapted to the new conditions of existence\ncreated by the development of his sensitiveness and his brain power.\nThis intellect is not proportioned to his organization, which has not\ndeveloped at the same rate; it protests against the discordances which\nadaptation has not yet had time to efface. But it will efface them in\nthe future.\n\n\n \u00a7 4. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH.\n\n\nThe greatest discrepancy of this kind is the knowledge of inevitable\ndeath without the instinct which makes it longed for.\n\nThere are immortal animals. Man is not of the number. He belongs,\nlike all highly organized beings, to the class of beings which have\nan end. They die from accident or from disease. They perish in the\nstruggle with other animals, or with microbes, or with external\nconditions. There are certainly very few, if there are any, which die a\nreally natural death. And so it is with man. We see old men gradually\ndeclining who appear to doze gently off into the last sleep, and become\nextinguished without disease, like a lamp whose oil is exhausted. But\nthis is in most cases only apparently so. Besides the fact that the old\nage to which they seemed to succumb is really a disease, a generalized\nsclerosis, autopsy always reveals some lesion more or less directly\nresponsible for the fatal issue.\n\nMan, like all the higher animals, is therefore subject to the law\nof lethality. But while animals have no idea of death and are not\ntormented by the sentiment of their inevitable end, man knows and\nunderstands this destiny. He has with the animals the instinct of\nself-preservation, the instinct of life, and at the same time the\nknowledge and the fear of death. This contradiction, this discordance,\nis one of the sources of his woes.\n\nWhether it be an accident or the regular term of the normal cycle,\ndeath always comes too soon. It surprises the man at a time when he\nhas not yet completed his physiological evolution; hence the aversion\nand the terror it inspires. \u201cWe cannot fix our eyes on the sun or on\ndeath,\u201d said La Rochefoucauld. The old man does not regard death with\nless aversion than the young man. \u201cHe who is most like the dead dies\nwith most regret.\u201d Man knows that he is not getting his full measure.\n\nFurther, all the really natural acts are solicited by an instinct, the\nsatisfaction of which is a need and a joy. The need of death should\ntherefore appear at the end of life, just as the need of sleep appears\nat the end of the day. It would appear, no doubt, if the normal cycle\nof existence were fulfilled, and if the harmonious evolution were not\nalways interrupted by accident. Death would then be welcomed and longed\nfor. It would lose its horror. The instinct of death would replace at\nthe wished for moment the instinct of life. Man would pass from the\nbanquet of life with no other desire. He would die without regret,\n\u201cbeing old and full of days,\u201d according to the expression used in the\nBible in the case of Abraham, Isaac, and Jacob. No doubt there are some\nanalogies to this in the insects which only assume the perfect form\nfor the purpose of procreation and immediately perish in their full\nperfection. In these animals the approach of death is blended with the\nintoxication of hymen. Thus we see some of them, the ephemerae, lose at\nthat moment the instinct of life and the instinct of self-preservation.\nThey allow themselves to be approached, taken, and seized, and make no\neffort at flight.\n\nBut what is this full measure of life which is imparted to us?\nMetchnikoff holds that the ages attributed to several persons in the\nBible are very probable. Abraham lived 175 years, Ishmael 137, Joseph\n110, Moses 120. Buffon believed in the existence of a ratio between the\nlongevity of animals and the duration of their growth. He fixed it at\n7:1. The animal whose development lasts two years would thus have 14\nyears of life. This law would give us 140 years, but the figure is too\nhigh, and Flourens has reduced the ratio to that of 5:1, which would\nstill give us 100 years. Plato died in the act of conversation at 81;\nIsocrates wrote his _Panathena\u00efcus_ at 94; Gorgias died in the full\npossession of his intellect at 107.\n\nTo reach the end of the promised longevity we must neither count on the\nelixir of life nor on the potable gold of the alchemists, nor on the\nstone of immortality which did not prevent its inventor, Paracelsus,\nfrom dying at the age of 58, nor on transfusion, nor on Graham\u2019s\ncelestial bed, nor on King David\u2019s gerocomy, nor on any nostrum or\nremedy. _Contra vim mortis non est medicamen in hortis_, said the\nSalernian school. What Feuchtersleben said is most true, \u201cThe art of\nprolonging life consists in not cutting it short,\u201d and it is a hygiene,\nbut a brilliant hygiene, such as that of which Metchnikoff traces us\nthe future lines, which will realize the desires of nature.\n\nAnd now shall we find that physiology has solved the enigma proposed by\nthe Sphinx, and that it has answered these poignant questions:\u2014Whence\ndo we come? whither do we go? what is the end of life? The end of life\nis, to the physiologist as well as to Herbert Spencer, the tendency\ntowards an existence as full and as long as possible, towards a life\nin conformity with real nature freed from the discordancies which\nstill remain; it is the accomplishment of the harmonious cycle of our\nnormal evolution. This ideal human nature, without discordancies, no\nlonger vitiated as it is at present but improved, will be the work of\ntime and science. Realized at last it will serve as a solid basis for\nindividual, family, and social morality. Healthy youth fit for action;\nprolonged, adult age, the symbol of strength; normal old age, wise in\ncouncil, these would have their natural places in harmonious society.\n\u201cGreat actions,\u201d said one of old, \u201care not achieved by exertions\nof strength, or speed, or agility, but rather by the prudence, the\nauthority, and the judgment which are found in a higher degree in old\nage.\u201d The old age of which Cicero here speaks is the ideal old age,\nregular and normal, and not the premature, deformed, incapable and\negoistic old age which results from a pathological condition. At the\nend of this full life, the old man being full of days, will crave for\nthe eternal sleep and will resign himself to it with joy....\n\nDeath, then, \u201cthe last enemy that shall be destroyed,\u201d to use the\nexpression of St. Paul, will yield to the power of science. Instead of\nbeing \u201cthe king of terrors,\u201d it will become after a long and healthy\nlife, after a life exempt from morbid accidents, a natural and longed\nfor event, a satisfied need. Then will be realized the wish of the\nfabulist:\u2014\n\n \u201c_I should like to leave life at this age, just as one leaves a\n banquet, thanking the host, and departing._\u201d\n\nHas this physiological solution of the problem of death the virtue\nattributed to it by Metchnikoff? Is it as optimistic as he thinks\nit is? The instinct of death supervening at the end of a normal and\nwell-filled cycle will no doubt facilitate to the aged their departure\non the great voyage. The wrench will no longer exist for the dead.\nWill it not exist for those who are left behind? And since the instinct\nof death can only exist about the time at which death is expected,\nwill the young man and the man of ripened years look with less horror\nthan to-day at the law which cannot be escaped, when they are in full\npossession of the instinct of life, but warned of the inevitability of\ndeath?\n\n\n\n\n INDEX OF AUTHORS.\n\n\n Altmann, 258\n\n Anaxagoras, 34\n\n Aquinas, St. Thomas, 3, 19, 248\n\n Aristotle, 3, 15, 18, 143, 146, 307\n\n Armstrong, 295\n\n Atwater, 137\n\n\n Bacon, vi., 35, 346\n\n Baker, 233\n\n Balbiani, 161, 165, 191, 206-7, 257\n\n Bang, d\u2019Yvor, 179\n\n Barthez, 3, 19, 24\n\n Beclard, 121\n\n Becquerel, 278\n\n Beijerinck, 193\n\n Benoit, 271\n\n Bernard, Claude, vi., 17, 27, 29, 32, 48, 50-4, 107, 109, 112, 119,\n 148, 150-1, 171, 190-2, 194, 197, 204, 210, 214-218, 220 _et seq._,\n 310, 318\n\n Bernoulli, John, 35, 73\n\n Bert, Paul, 194\n\n Berthelot, 91, 98, 128-130, 152, 204, 296\n\n Berthollet, 82\n\n Berzelius, 117\n\n Bichat, 3, 6, 20, 22, 27-30, 35, 55, 158, 170, 198, 308\n\n Blumenbach, 46\n\n Bo\u00eb, Sylvius Le, 35-6\n\n Boerhaave, 35, 147, 245\n\n Bohr, 29-30\n\n Bokorny, 324\n\n Boltzmann, 265\n\n Bonnet, 23, 49\n\n Bordeu, 3, 10, 19, 22, 24, 312\n\n Borelli, 35\n\n Boscovitch, 37, 248\n\n Bose, 264\n\n Bossuet, 11\n\n Bouasse, 73, 264-5\n\n Boullier, 12\n\n Bourdeau, 237, 242\n\n Boussingault, 149\n\n Brandt, 257\n\n Bravais, 282\n\n Brillouin, 264, 273\n\n Brown, 266 _et seq._\n\n Br\u00fccke, 44\n\n B\u00fcchner, 325\n\n Buffon, 46, 254, 357\n\n Bunge, von, 3, 14\n\n Burdon, Sanderson, 176\n\n Busquet, 175\n\n B\u00fctschli, 161-2, 175\n\n\n Cabanis, 245, 246\n\n Cailletet, 272\n\n Calkins, 327, 338\n\n Calvert, 271\n\n Candolle, 20\n\n Cardan, 261\n\n Carnot, 72-3, 89, 92 _et seq._, 101, 114, 121\n\n Charpy, 237, 271\n\n Chauffard, 3, 10, 11, 294\n\n Chauveau, 75, 103, 108, 123, 130, 145, 213\n\n Chevreul, 32\n\n Chossat, 152\n\n Cicero, 347, 359\n\n Clausius, 67, 88\n\n Cohn, 191, 252\n\n Cohnheim, 341\n\n Colding, 58 _note_, 90\n\n Colin, 52\n\n Comte, 189-190, 310\n\n Confucius, 309\n\n Coulomb, 76, 264, 273\n\n Crookes, 295, 302\n\n Cuvier, 3, 6, 27-8, 105, 120, 152, 190, 198, 308, 310, 319\n\n\n D\u2019Alembert, 20, 59 _note_, 90, 92\n\n Dantec, Le, 48, 52, 55 _note_, 110, 148, 173, 198, 201, 203, 213, 216,\n 220, 223 _et seq._, 231, 246, 261, 285, 296, 340\n\n D\u2019Arsonval, 126\n\n Darwin, 3, 46, 167, 258, 354\n\n Dastre, A., 192, 198 _note_\n\n Davy, Sir Humphry, 61, 80\n\n Delafosse, 282\n\n Delage, 208\n\n Demange, 349\n\n Democritus, 34, 146\n\n Descartes, 3, 9, 35, 37, 40, 73, 91, 98\n\n Despretz, 126\n\n Diderot, 245, 246\n\n Drechsel, 183\n\n Dressel, 20\n\n Dubois-Reymond, 44, 58 _note_, 253\n\n Duclaux, 119, 137, 184, 324\n\n Dufour, 297\n\n Duguet, 264\n\n Duhem, 62, 264, 265\n\n Dulong, 126\n\n Dumas, 115, 149, 151-2\n\n\n Epicurus, 35, 146\n\n Ehrlich, 176\n\n Errera, 52, 193-4, 237, 153, 295, 302 _et seq._\n\n Euclid, v.\n\n\n Faye, 260\n\n Feuchterslehen, 358\n\n Flemming, 161\n\n Flourens, 20-1, 152, 208, 306, 358\n\n Fouill\u00e9e, 242\n\n Fromann, 161\n\n Fuerth, 183\n\n\n Galen, 25, 55, 143\n\n Galeotti, 180\n\n Galileo, 73, 91, 98, 197, 241, 260\n\n Gardair, 19, 248\n\n Gautier, A., 3, 32, 36, 39, 176, 233, 324\n\n Gernez, 237, 288, 295 _et seq._\n\n Glisson, 27\n\n Goethe, 170, 312\n\n Gouy, 266, 268\n\n Grimaud, 19\n\n Gruber, 165, 206, 257\n\n Guignard, 161\n\n Guillaume, 237, 262, 264, 271, 277\n\n Guillemin, 237\n\n Guldberg, 83\n\n\n Harbermann, 183\n\n Haeckel, 3, 46, 164, 167, 246, 251\n\n Hales, 43\n\n Haller, 27\n\n Hamilton, Sir W. Rowan, 67\n\n Hammarsten, 180\n\n Hartmann, 276, 346\n\n Harvey, 43, 160\n\n Ha\u00fcy, 282\n\n Hegel, 170, 331\n\n Heidenhain, 3, 29, 30-1\n\n Heitzmann, 161\n\n Helmholtz, 44, 56, 58, 67, 90, 97, 99, 252\n\n Helmont, van, 3, 21, 26, 33, 146, 250\n\n Henninger, 302\n\n Heraclitus, 34\n\n Hertwig, 167\n\n Hertz, 88\n\n Hess, 91, 98\n\n Hippocrates, 146\n\n Hirn, 126\n\n His, 46\n\n Hlasitwetz, 183\n\n Holbach, d\u2019, 354\n\n Hoogewerf, 303\n\n Hopkinson, 271\n\n Humboldt, W. von, 354\n\n\n Ingenhousz, 115\n\n Izolet, 247\n\n\n Joule, 53 _note_, 90-1, 93, 133 _et seq._, 143, 152\n\n\n Kant, 312, 319\n\n Kaup, 213\n\n Kaufmann, 126\n\n Kelvin, Lord, 63, 67, 90, 92, 251-2, 264;\n and the idea of energy, 66\n\n Kepler, 29, 241\n\n Klemm, 323\n\n Koelliker, 160\n\n Kossel, 174, 179, 130-1, 136 _et seq._\n\n Kuhne, 45\n\n Kuhm, 216\n\n Kuliabko, 23, 311\n\n Kunstler, 157, 161-2, 175\n\n Kuppfer, 161\n\n\n Lammettrie, 147\n\n Lamarck, 46\n\n Lapparent, 284\n\n Lapicque, 140, 145\n\n Langley, 216\n\n Laplace, 43, 63, 126, 260\n\n Laulani\u00e9, 103\n\n Laurie, 271\n\n La Rochefoucauld, 356\n\n Lavoisier, 3, 28, 30, 36, 43, 65, 117, 121, 126, 128, 143, 176, 296\n\n Lea, 216\n\n Le Ch\u00e2telier, 85, 92\n\n Lechatelier, H. and A., 271\n\n Lecocq de Boisbaudran, 295\n\n Leeuwenhoek, 232\n\n Lef\u00e8vre, 126\n\n Legallois, 21\n\n Leydig, 161-2\n\n Liebermeister, 136\n\n Liebig, 26, 53 _note_, 117\n\n Lilienfeld, 179, 247\n\n Locke, 23\n\n Lodge, 271\n\n Loeb, 43, 167, 327, 341\n\n Loew, 324\n\n Loisel, 339, 341\n\n Lorry, 21\n\n Longet, 52\n\n Lowitz, 297\n\n Loye, 192\n\n Ludwig, 44, 215\n\n\n Mach, 41, 62\n\n Magendie, 43, 143\n\n Magy, 37\n\n Malgaigne, 153\n\n Mallard, 284\n\n Marinesco, 231, 328\n\n Markel, 349\n\n Maspero, 3, 234\n\n Matthiesson, 271\n\n Maupas, 337\n\n Maxwell, 88\n\n Mayer, R., 56, 58, 89, 90, 97, 99, 101\n\n Mering, von, 133, 136\n\n Metchnikoff, 327 _et seq._\n\n Miescher, 174, 179\n\n Milne-Edwards, 152, 195\n\n Minot, 341\n\n Miura, 137\n\n Mori, 145\n\n M\u00fcller, 20, 27, 341\n\n Murato, 45\n\n\n Naegeli, 168\n\n Needham, 46\n\n Newton, 58 _note_, 70, 90-1, 93\n\n Noorden, van, 129, 137, 140, 210\n\n Nussbaum, 165, 206, 215, 217\n\n\n Obermeyer, 271\n\n Osmond, 237, 271\n\n Ostwald, 41, 62, 67, 85, 104, 237, 258, 289, 295 _et seq._\n\n\n Paracelsus, 26, 146, 312\n\n Pascal, 74, 161\n\n Pasteur, 53, 191, 222 _et seq._, 237, 250, 288, 346\n\n Payen, 151\n\n Persoz, 152\n\n Petit, 180\n\n Pettenkofer, 210\n\n Pfeffer, 175, 193\n\n Pfl\u00fcger, 12, 56, 135, 144, 176, 210, 213\n\n Philpotts, 46\n\n Pictet, 233\n\n Pitcairn, 35\n\n Plato, 35, 307\n\n Plosz, 180\n\n Poincar\u00e9, 62\n\n Poisson, 63\n\n Preyer, 192, 252 _et seq._\n\n Priestley, 115\n\n Ptolemy, v.\n\n Pythagoras, 18\n\n\n Rauber, 237, 288\n\n Raulin, 191\n\n Regnault, 117\n\n Reinke, 3, 32\n\n Renan, 240\n\n Ribbert, 208\n\n Ribot, 247\n\n Riche, 271\n\n Richet, 50, 126, 140\n\n Richter, 252\n\n Rindfleisch, 4\n\n Roberts-Austen, 237, 271-2\n\n Robin, 62, 177\n\n Rosenthal, 126\n\n Rouvier, 160\n\n Roux, 46, 165\n\n Rubner, 129, 130, 140 _et seq._, 210\n\n Rumford, 80\n\n\n Sabatier, 242\n\n Sachs, 161, 194\n\n Salles-Guyon, 252\n\n Sanderson, Burdon, 176\n\n Scaliger, 241\n\n Schleiden, 159\n\n Schopenhauer, 346\n\n Schwartz, 162\n\n Schultze, 160, 326\n\n Schultzenberger, 174, 162 _et seq._\n\n Secchi, 88\n\n Seguin, 58 _note_, 90\n\n Senebier, 115\n\n Siven, 145\n\n Spallanzani, 43, 233\n\n Spencer, Herbert, 46, 247, 354, 358\n\n Spring, 272\n\n Stahl, 3, 9, 12, 35, 146\n\n Stammreich, 137\n\n Stead, 237\n\n Stohmann, 129, 130, 140\n\n Strassburger, 161, 350\n\n Swann, 159\n\n Swift, 262\n\n\n Tait, 53 _note_, 66\n\n Tammann, 237, 253, 295 _et seq._\n\n Thales, 34\n\n Thomson, Sir J. J., 279\n\n Tissot, 12\n\n Tomlinson, 264\n\n Trembley, 22, 206\n\n Tsubo\u00ef, 145\n\n Tylor, 8\n\n\n Verworn, 206, 252, 257\n\n Violette, 295\n\n Virchow, 318, 326\n\n Voit, 119, 133 _et seq._, 210\n\n Vries, de, 46, 258, 355\n\n Vulpian, 24\n\n\n Waage, 83\n\n Waller, 47, 206\n\n Wallerant, 282-3\n\n Warburg, 264\n\n Watt, 76\n\n Weismann, 46, 167, 336, 343\n\n Wertheim, 264\n\n Whitman, 46\n\n Widersheim, 351\n\n Wiedermann, 264\n\n Wiesner, 167\n\n Willis, 36, 147\n\n Winternitz, 126\n\n\n Yung, 233\n\n\n Zuntz, 133, 136, 210\n\n\n\n\n INDEX OF SUBJECTS.\n\n\n Activity, functional and vital, 106 _et seq._, 217 _et seq._\n\n Aerobia, 193\n\n Age, old, Book v.\n\n Albumin, 178\n\n Albuminoids, 178\n\n Alcohol, 136\n\n Alimentation, 116 _et seq._\n\n Alloys, structure of, 273\n\n An\u00e6robia, 193\n\n Animism, 6, 7, Chap. ii., _passim_\n\n Annealing, 275\n\n Apposition, 291\n\n Archeus, the, 25, 26, 33\n\n Arginin, 187\n\n Assimilation, law of functional, 110, 213\n\n Atomicities, satisfied, 185\n\n Atrophy, 326\n\n Attraction, energy of position, 64\n\n\n Balance, sheet, nutritive, 118\n\n Beliefs, primitive, 239\n\n Bioblasts, 253\n\n Biophors, 167\n\n Blas, the, 25, 33\n\n Blood, lavage of, 192\n\n Brain, and death, 315\n\n Butylic ferments, 193\n\n Butyric ferments, 193\n\n\n Calorie, 125 _note_\n\n Calorimeter, ice, 126;\n bomb, 128\n\n Caprice, of Nature, 45\n\n Cause, final, 45\n\n Cells, 48, 147;\n somatic and sexual, 343\n\n Cellular theory, 158 _et seq._\n\n Centrosome, 163\n\n Chromosome, 165\n\n Cicatrization, 287\n\n Complex, homogeneity of the, 245\n\n Conductibility, 26\n\n Consciousness, in brute bodies, 244 _et seq._\n\n Continuity, principle of, 242, 247\n\n Contractility, 26\n\n Contraction, energy of static and dynamic, 75\n\n Conservation, of energy, 58;\n of force, 58\n\n Crystals, 200 _et seq._, 237 _et seq._, 281 _et seq._\n\n Cytoplasm, 161 _et seq._\n\n\n Death, apparent, 232;\n senescence of, 305 _et seq._;\n cellular, 321 _et seq._\n\n Decentralization, 24\n\n Degeneration, 326\n\n Destruction, functional, 106;\n organic, 211;\n of living matter, 213\n\n Determinism, 49\n\n Digestion, of plants and animals, 152 _et seq._\n\n Direction, idea of, 16\n\n Dominants, 33, 39, 45\n\n Dyne, the, 71\n\n\n Effort, of force, 71\n\n Electrolysis, 272\n\n Energetics, 39, 56;\n laws of biological, 105 _et seq._, 229;\n alimentary, 116 _et seq._\n\n Energy, 37, Book ii., _passim_;\n origin of idea of, 57;\n theory of, 62;\n the only objective reality, 64-5;\n and kinetic conception, 67;\n mechanical, 69, 73;\n of contraction, 75;\n kinetic, 76, 83;\n potential, 76, 83;\n virtual, 77;\n of motion and position, 79;\n thermal, and its measurements, 80-2;\n chemical, and its measurements, 81-2;\n chemical and potential, 83;\n materialization of, 84;\n transformations of, 85 _et seq._;\n luminous, 86 _et seq._;\n conservation of, 90 _et seq._;\n capacity of conversion of, 93;\n in biology, 97;\n in living beings, 99 _et seq._;\n physical, 99 _et seq._;\n vital, 99 _et seq._\n\n Ether, 89\n\n Equivalence, law of, 91\n\n Excitability, 26-7\n\n\n Fatigue, of metals, 264\n\n Ferments, butylic and butyric, 193\n\n Filiation, 250\n\n Finalism, 43\n\n Food, a source of energy, 118 _et seq._;\n thermogenic and biothermogenic types of, 131 _et seq._;\n dynamogenic type of, 143;\n nitrogenous, 143;\n of animals and plants, 153 _et seq._\n\n Force, directive, 16 _et seq._, 32, 39, 48;\n vital, 45;\n an anthromorphic notion, 71;\n and work, 74;\n measurement of, 71;\n plastic, 143;\n plastic and morphoplastic forces, 208\n\n Form, specific, 199 _et seq._, 281\n\n Fruits, acids of, 136\n\n\n Gemmules, 167, 258\n\n Generation, spontaneous, 249 _et seq._, 294 _et seq._\n\n Globulin, 178\n\n Glycerine, crystals of, 302\n\n Glycogen, 108, 153 _et seq._\n\n Gramme, 71\n\n\n Heat, a mode of motion, 61;\n r\u00f4le of animal heat, 122;\n mechanical equivalent of, 81;\n an excretum, 114;\n a degraded form of energy, 88;\n converted into work, 92\n\n Heterogeneity, 38, 61\n\n Histones, 179, 182 _et seq._\n\n Horse-power, 75\n\n Hyaloplasm, 161\n\n\n Iatro-chemistry and mechanics, 34-5\n\n Idioblasts, 167\n\n Infusoria, death of, 337\n\n Instability, 188 _et seq._\n\n Instinct, of life and death, 345 _et seq._\n\n Intussusception, 291\n\n Invariant, mass the first, 63\n\n Irreversibility, of vital energies, 104\n\n Irritability, 27, 196 _et seq._\n\n Isodynamism, 142\n\n Isomorphism, 286\n\n\n Ka, the, 8\n\n Kilogrammetre, 72, 75;\n per second, 75\n\n Kilowatt, 76\n\n Kinetic theory, 39, 62\n\n Knot, the vital, 21\n\n\n Leucines, 183\n\n Leucites, 163\n\n Life, defined, 28;\n latent, 233;\n physico-chemical theory of, 36;\n elementary, 321\n\n Linin, 163\n\n\n Mass, and matter, 63\n\n Materialism, 34\n\n Matter, 37, 60, 62;\n and mass, 63;\n two kinds of, 63;\n life of, 236 _et seq._;\n brute and living, 249 _et seq._;\n organization and constitution of, 255 _et seq._;\n defined as extension, 64;\n conservation of, 65\n\n \u201cMemory,\u201d of metals, etc., 265\n\n Merotomy, 47\n\n Metabolism, 117\n\n Metazoa, evolution and death of, 340 _et seq._\n\n Meteoric cosmozoa, 252\n\n Micellar theory, 166 _et seq._\n\n Microcosms, 163\n\n Micro-organisms, culture of, 297\n\n Mitomes, 169\n\n Mobility of stars, 260\n\n Modality, twofold, of soul, 12\n\n Molecules, organic, 254\n\n Monism, 34, Chap. iv. _passim_, 63\n\n Montpellier, the school of, 35\n\n Motion, cause of, 71;\n kinetic conception of molecular, 263\n\n Morphogenesis, idea of, 46\n\n Movements, internal of bodies, 262;\n Brownian, 266 _et seq._\n\n Mutability, 80, 188 _et seq._;\n of living matter, 259 _et seq._;\n of brute bodies, 259 _et seq._\n\n\n Necrobiosis, 326\n\n Neo-vitalism, 15, 29, 32\n\n Neurility, 27\n\n Nickel, steels, 277\n\n Nisus _formativus_, 46\n\n Nous, the, 18, 239\n\n Nucleins, 179, 180 _et seq._\n\n Nucleo-albuminoids, 178;\n -proteids, 177 _et seq._\n\n Nucleus, 163 _et seq._;\n hexonic, 186\n\n Nutrition, directed, 205, 209 _et seq._, 227 _et seq._, 290 _et seq._\n\n\n Organogenesis, 282\n\n Organs, organization of, 314;\n death of, 315;\n perfect, 319\n\n\n Pangenes, 167\n\n Panspermia, 252\n\n Parameter, mass the mechanical, 63\n\n Phenomena, vital, 44, 51, 189;\n modes of motion, 61\n\n Photography, colour, 277\n\n Physiology, general, 56;\n cellular, 56\n\n Plants, and immortality, 330\n\n Plasomes, 167\n\n Plurivitalism, 25\n\n Power, 70, 75\n\n Principle, vital, 15 _et seq._\n\n Properties, vital, 25, 103\n\n Proteids, 178\n\n Protoplasm, 109 _et seq._, 175 _et seq._, 231 _et seq._;\n life in crushed, 257 _et seq._\n\n Protozoa, immortality of, 352 _et seq._\n\n Psyche, 239\n\n Pyrozoa, 253\n\n\n Regeneration, normal, 205;\n accidental, 206\n\n Reparation, mechanism of, 288\n\n Repose, functional, 109, 217 _et seq._\n\n Reserve stuff, 106 _et seq._, 212, 230 _et seq._\n\n Rachidian, soul, 12\n\n\n Senescence, 305 _et seq._\n\n Sensibility, in brute bodies, 244\n\n Solidarity, of anatomical elements, humoral and nervous, 317\n\n Soul, the, 7 _et seq._\n\n Space, 69\n\n Specificity, vital, 48\n\n Spireme, 165\n\n Spongioplasm, 162\n\n States, initial and final, 128\n\n Swelling, 167\n\n Synthesis, organizing, 109\n\n\n Tagmata, 169, 175\n\n Teleology, 43\n\n Tetanus, bacteria of, 193\n\n Thermogenesis, 140\n\n Time, 69\n\n Tonus, muscular, 119\n\n Trees, and immortality, 330 _et seq._\n\n Tripod, vital, 2, 314\n\n Turgescence, 168\n\n\n Universe, the, mechanical explanation of, 60;\n the end of the, 95\n\n Unity, chemical, of living beings, 173 _et seq._, 321;\n morphological, 321\n\n\n Vacuoles, 113\n\n Vibrion, septic, 193\n\n Vis viva, 73\n\n Vital properties, theory of, 29 _et seq._\n\n Vitalism, 6, 7, Chap. iii. _passim_;\n physico-chemical, 29\n\n Vitality, phenomena of, 216\n\n Vortex, vital, 105, 120, 229 _et seq._\n\n Vulcans, 26-7\n\n\n Weight, energy of position, 64;\n conservation of, 65;\n movement under action of, 271 _et seq._\n\n Work, 70, 72;\n and force, 74, 77;\n converted into heat, 92;\n physiological, 103\n\n\n Xanthic bases, 180\n\n\n Zones, metastable and labile, 301\n\n\n THE WALTER SCOTT PUBLISHING COMPANY, LTD., FELLING-ON-TYNE.","title":"Life and death","tradition":"philosophy-ethics","translated_text":null,"word_count":96647}