LUBGBBE “Se I EMPORARY | ZA LA Vl LOIISLI ALATA ALLS BAUAt , SY Zz ~ S oN) ZY Serre SSS \ ‘ \ \\ WE < 4 AE ad 8 | y N CORNELL UNIVERSITY |: LIBRARY FROM. The Dept. of Zoology ———— wana 003 175 Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003175381 BIOLOGY. BIOLOGY. BY DR. CHARLES LETOURNEAU. TRANSLATED BY WILLIAM MACCALL: “ Pro Veritate.” WITH EIGHTY-THREE ILLUSTRATIONS. LONDON: CHAPMAN AND HALL, 193, PICCADILLY. PHILADELPHIA: J. B LIPPINCOTT AND CO. 1878. LONDON : R. CLAY, SONS, AND TAYLOR, PRINTERS, BREAD STREET HILL, QUEEN VICTORIA STREET. ‘ PREFACE, THE word Biology, which seems to have been employed for the first time by Treviranus, is far from bearing in the scientific vocabulary a completely settled import. It may not be unprofitable to determine the sense of the word. Etymologically it signifies literally “science of life,” and embraces everything relating, intimately or remotely, to the study of organised beings ; that is to say, a whole group of sciences, among which is comprehended Anthropology, for instance. It is in this encyclopzdical sense that Auguste Comte took the word “Biology,” though as far as we our- selves are concerned we intend. to give it a sense much more restricted. Under the designation “Biology,” we merely place the exposition and the coordination of all the great facts and great laws of life, or nearly what is usually under- stood by “ General’ Physiology,” when this denomination is applied to the two organic kingdoms. In this volume we have simply attempted to state concisely what life is, and how organised beings are nourished, grow, are reproduced, move, feel and think, vi PREFACE. Even while limiting ourselves fo this comparatively re- stricted domain, we have had to consider, to group, to con- dense and to classify, an enormous mass of facts derived from all the natural sciences. Among these facts, numerous as the stars of the heaven and the sands of the sea, we have been compelled to make a choice, and to select as much as possible what was most important, most significative, most luminous. We hope that the learned men who devote themselves to special subjects may find in our modest production some new combinations, perchance some of those general views which are sometimes lacking to certain men in other respects very distinguished, but who abide too closely in this or that district of knowledge, as happens often in this age when the division of scientific labour is carried to excess. Nevertheless, we do not write for scientific men. We wish especially to be read by the mass of enlightened people, whom our very incom- plete system of public instruction has left almost unacquainted with Biology. In effect, our best establishments for secondary instruction limit their ambition to imparting sufficiently complete ideas of physics, and very incomplete ideas con- cerning chemistry; but they stop too timidly on the threshold of Biology, the mysteries of which are accessible only to a small number of special men. This is a defect exceedingly deplorable, exceedingly prejudicial to general progress. It is on account of this defect that so many false and even pernicious ideas continue to find acceptance and empire in public opinion; hence it is, in a great measure, that true philosophy, or rather that philosophy which is alone solid and sound, that which flows directly and legitimately from PREFACE. vii observation and experiment, has such difficulty in diffusing itself. The object of our little book is to remedy this serious educational deficiency in those who are otherwise enlightened. It is therefore a work of vulgarisation. Certain scientific men, too strictly confined within their own circle, and whose horizon is bounded by the walls of their laboratories, pro- nounce, with disdain, though unjustly, this term vulgar- isation. To find the truth is surely a noble labour; but what is the value of the discovered truth, if care is not taken to propagate it, to introduce it into the patrimony of general knowledge ? On the other hand, it must be granted that the work of popularising has been brought somewhat into disrepute by a crowd of pseudo-scientific publications, the authors of which, trusting too little to the intelligence of the reader, either administer only an infinitesimal dose of science, or think themselves obliged to dilute the main idea with a deluge of light or pleasing words, sacrificing thus at once to the most amiable and most dangerous of our national peculiarities. Science only deserves its name upon condition of preserving a somewhat austere nobleness. For our part we have taken care not to rob science of that which constitutes its strength, and for this we trust the reader will give us credit. In our opinion there is not a person of moderate intelligence who will not be able, at the cost of a slight mental effort, to read and comprehend this book ; and we think also that by such a perusal of it, sufficiently clear and complete ideas of Biology will have been imparted. This is not a polemical work, but rather an exposition Vili PREFACE. of facts. Nevertheless, amongst these facts are some which are indisputable ; also, when we have met with them, we have not hesitated to formulate the conclusions or induc- tions which. resulted from them. We have always done this temperately and with brevity, and without having any other motive than the love of truth. We trust that this volume may be read, and that profitably, and that it may awaken, in a large number of its readers, love of and respect for science, namely, that which alone, in these sad times, is at once a refuge and a hope. Cu. LETOURNEAU. BIOLOGY. BOOK I. OF ORGANISED MATTER IN GENERAL. % CHAPTER I. CONSTITUTION OF MATTER.,——UNITY OF SUBSTANCE IN THE ORGANIC WORLD AND IN THE INORGANIC WORLD. THE sciences of observation demand at the outset from him who wishes to cultivate them an act of faith. Though it is per- fectly incontestable that the exterior world manifests itself to us solely by exciting in our mind an incessant series of phe- nomena of consciousness, of phenomena called subjective, we are nevertheless compelled, unless we wish to plunge into the doubt applauded by Pyrrho and Berkeley, to believe our senses as honest and sincere witnesses when they signalise to us the exist- ence, apart from our own being, of a vast material universe, the elements whereof, without pause in movement, awaken in us, by acting on our organism, impressions, sensations, and consequently ideas and desires. The exterior world exists independently of our conscious life ; it was when as yet we were not; and it will be when we are no 5 B € 2 BIOLOGY. [Boox 1. more. Without stopping, asa few years ago M. Littré did, to discuss the point whether the certitude of the existence of the external world is of first or second quality, leaving aside every metaphysical refinement, we must first firmly believe in the real existence of the external world ; because all our senses cease not to cry to us in every tone that the objective, the Non-Me of the psy- chologists, is not a chimera, because the contrary opinion would strike with nullity all observation, all experience, all reasoning, all knowledge. The reality of the exterior world once admitted, and man never having been led to doubt that reality, except through a species of intellectual depravation, people naturally inquired what could be the internal constitution of the substance of the universe. They suspected that behind the appearance infinitely mobile and varied of the exterior phenomena there might exist a general and related force. Our object in this work not being to pass in review the opinions or the reveries of the different philosophical schools, we make haste to expound the most pro- bable theories and systems, those which observation has confirmed, and which by slow degrees have conquered in science shen right of citizenship. Leucippus seems to have been the first to have had the intuition of the most rational theory on the constitution of the universal substance. In his opinion this substance is a discontinuous mass of granules, solid, infinitely small, separated by void spaces. It is “the void mingled with solid,” according to an expression of Bacon. Democritus admitted that these primordial granules were full, impenetrable, moreover insecable, and, for this last reason, he called them atoms.'| But the conception of atoms, full and dis- 1 For what is it that Democritus says ?—‘‘That there are substances in infinite number, which are called atoms, because they cannot be divided, which are, however, different, which have no quality whatever, are impassible, which are dispersed here and there in the infinite void, which approach each other, gather themselves together, enter into conjunction ; that from these assem- blages one result appears as water, another as fire, another as tree, another Cuar. 1.] CONSTITUTION OF MATTER. 3 persed through the limitless void of the universe, did not furnish a sufficiently precise account of the constitution of bodies. Epicurus appeared, whose doctrine was so magnificently sung by the great poet Lucretius. He immensely improved the atomic theory of Leucippus and Democritus by vivifying atoms, and by supposing them endowed with spontaneous movement. From the mobility of atoms resulted their various aggregations and the dissemblances of bodies. According to Epicurus, atoms of necessity mingled together, intertwined, literally caught and clung to each other. A philosopher who had the talent to preach and to. propagate in France the atomic theory without seeming to offend the orthodoxy of his epoch, which was still very suspicious, Gassendi, restored to honour the atomic doctrine of the ancients. He admits, according to the expression of Epicurus, that “that which is moves in that which is not,” that is, that atoms are not in contact, but that they are separated by void spaces. Thus then, according to this theory, the world is composed of an innumerable quantity of atoms, mobile, infinitely small, distant from each other. These atoms are in a perpetual state of movement, rushing toward each other, repelling each other, for they have their sympathies and antipathies. It is from the diversity of their affirlities that result their exceedingly diversified modes of grouping and the variety of the external world. It is by their vibrations, their oscillations that they reveal themselves to man by impressing his organs of sense. They have as essential qualities inalterability, eternity. When they gather together, new bodies are formed ; when they dis- aggregate, bodies previously existing dissolve and seem to vanish. They are unhewn stones which have passed, pass, and are as man ; that everything consists of atoms, which he also calls ideas, and that nothing else exists, forasmuch as generation cannot arise from that which is not while likewise what exists cannot cease to be, because atoms are so firm that they cannot change nor alter nor suffer.”—PLuTarcH, Miscellancous Works: Against the Epicurean Colotes; Amyot’s translation, Clavier's edition, vol, xx., Paris, 1803. B2 4 BLOLOGY. [Book 1. destined evermore to pass from one edifice to another. Their totality constitutes the general substance of the ‘universe, and, in reality, this general substance undergoes no other changes than modifications in the distribution of its constituent ele- ments, All the phenomena, all the varied aspects, all the revolutions of the universe can be referred essentially to simple atomic displacements. This grand theory, so admirably simple and seductive, would be nothing but a brilliant speculation, if facts, numerous and rigorously observed, did not now serve it as basis and demon- stration. We rapidly enumerate the most important of these facts, which belong for the most part to the domain of Physics and Chemistry. Wenzel, Richter, Proust proved first of all that in chemical compositions and ‘decompositions, bodies combine according to proportions rigorously defined. Dalton formulated the law of multiple proportions, and deduced therefrom naturally that matter is constituted by atoms extended, having a constant weight, and that those atoms are of various species. When atoms of the same species come into juxtaposition, we have what we call simple bodies, such as hydrogen, oxygen, azote. On the contrary, the bodies called compound result from the juxtaposition of atoms of diversified nature, whence come acids, salts, oxides, and also all the unstable and complex compounds which constitute organic substances. This is not all: to the law of Dalton the law of Avogadro and of Ampére is adjoined. This last law establishes that all gases, temperature and pressure being equal, have the same elastic force. But as this force is probably due to the shock of atoms or groups of atoms, molecules, on the sides of the vessels which imprison the gases, we must admit that in the conditions aforesaid all gases contain, under the same volume, the same number of molecules or of atoms. Finally, Dulong and Petit have been able to show, experi- mentally, that the atoms of simple bodies all possess the same specific heat, Cuap. 1.] CONSTITUTION OF MATTER. 5 All these great laws, slowly evolved by observation and ex- periment, have transformed into a solid scientific theory the brilliant but vague intuition of the thinkers of ancient Greece. With ground so firm to rest on, chemistry has been able to particularise more, to study in some sort the individual cha- racter of atoms; in scientific language, it has arrived at the notion of atomicity. Atoms have as general characteristics extension, impenetra- bility, indestructibility, and eternal activity. But these general characteristics exclude not a number of specific differences. The progress of chemistry will no doubt show us what amount of truth there is in the hypotheses of Dumas and of Lockyer, according to which the simple bodies of chemistry as it now exists are merely indecomposed bodies. According to this as- sumption our metals and our metalloids are simple modifi- cations of a single substance, probably hydrogen, the atoms thereof forming different moleeular groupings. In the present ‘state of science, these ideas, as yet purely hypothetical, can be passed by; and relying for the present on the great laws of Dalton, Ampétre, Dulong, and Petit, we have the right to consider the simple bodies of contemporary chemistry as repre- senting groups of atoms identical among themselves in each simple body, but specifically different from one simple body to another. Now each of these atomic species has its individual energy, its own affinities. In the group of the other atomic species it has friends, it has indifferents, it has enemies. It willingly unites itself to the first, neglects the second, refuses, on the contrary, to combine with the last. Moreover, this faculty of attracting and of being attracted attains in each atomic species a different degree of energy. Whence we may conclude that there are in the different atomic species differences of mass and of form. In aggregating themselves thus, according to their affinities, atoms arrange themselves into small systems, having in each body a special structure. These atomic systems are called molecules. The atoms of alkaline metals, such as potassium and sodium, a 6 BIOLOGY. {Book 1 cannot. fix each more than one atom of chlorine or of bromine they are monvatomic, as, for instance, hydrogen. Calcium, barium strontium, in order that their attractive power may be saturated need to fix two atoms of chlorine; they are diatomic, as, fo instance, oxygen. Phosphorus, which in the perchlorure o phosphorus succeeds in fixing five atoms of chlorine, is pentatomic It is these inequalities in the mode and the power of combina tion, in the capacity of saturation, which we call the atomicity o each atomical species, designating specially by that expressioi the maximum capacity of saturation. However, hereby is by nm means implied that a pentatomic species, for instance azote, can -not combine with less than five atoms. Azote, which fixes fiv atoms in the chlorohydrate of ammonia (AzH*(1), is not mor than ériatomic in ammoniac gas (AzH®), and is only diatomic in the bioxide of azote. For the sake of greater clearness, thi denomination atomicity is reserved to designate the capacity o absolute saturation. The capacities of inferior saturations ar called quantivalences. Thus then azote is pentatomic, but it i: trivalent in gas ammoniac, and so on. This notion of atomicity has thrown a great light on thi ultimate texture of bodies, and also on the march hither anc thither of atoms in various combinations. In effect, free o1 combined, every atom tends to saturate itself by the annexion o: other atoms. If, for instance, a tetratomic atom has combinec¢ with two atoms only, it ceases not to tend to saturate its attrac tive force; it strives to fix two atoms more. But these twc atoms once found, no other simple body can combine with ow tetratomic atom, unless by displacing one or two of its atoms and becoming their substitute. If, for instance, we take from a carburet of saturated hydrogen an atom of hydrogen, the molecule thus mutilated can unite itself to an atom of chlorine But the chlorine is monoatomic ; this, however, does not hindei it from fixing the complex molecule of the carburet, impoverished to the extent of an atom of hydrogen. The reason is that certain atomic groups, certain molecules, can play in combina tions the part of a single atom. They are what we call com Cuap. 1.] CONSTITUTION OF MATTER. 7 pound radicals. This notion of compound radicals has a pre- dominant importance in the chemistry of organic substances, so called because nearly altogether they constitute the substance of living bodies. It simplifies extremely their apparent com- plexity. It is thus that, according to Mulder, the formula of albumine is 10(C*°H*!N50)+S?Ph. If we limit ourselves to totalising the atoms, this formula gives C4°H310N%Q0120 + §?Ph, a molecule of frightful complication. But if we admit a com- pound radical, proteine (C#°H?!N5Q!2), comporting itself as a simple atom, the molecular structure of albumine is enormously simplified : it approaches that which we are accustomed to meet in the chemistry called mineral. It is probably also from this notion of compound radicals that we must seek the explanation of what has been called isomeria. If bodies having the same elementary composition, such as the tartaric and paratartaric, matic acid, citric acid, sugars, gums, have nevertheless distinctive properties, we must probably attribute the dissimilarities to differences of molecular structure, to the existence, in the very heart of these isomeric bodies, of dissimilar compound radicals. There is another notion not less important than that of com- pound radicals for the easy comprehension of the formulas of the chemistry called organic, the notion, namely, of autosatura- tion. In effect, the atomicity of a simple body does not always expend itself on atoms of a different species ; it may manifest itself between atoms of the same species. The atoms of carbon, for instance, can saturate themselves. An atom of carbon, which | is tetratomic, — ¢ —, may, by expending merely a quarter of its atomicity, unite itself with another atom of carbon, which, in its turn, will neutralise in this combination a quarter of its attrac- tive energy ; there will result thus therefrom a molecule hexa- valent, that is to say, capable of still enchaining six atoms: 8 BIOLOGY. [Book 1. Let a,third atom of carbon then unite itself to this molecule, we have an octovalent molecule : eee i Finally, the adjunction of a fourth atom of carbon gives a decavalent compound : bobo —e—e—c—ec— a a | This notion of autosaturation has enabled us to systematise a quantity of facts of organic chemistry, to create rationally new compounds, to classify and to seriate groups. We owe to it the theory of alcohols, and that of hydrocarburets.? The preceding pages contain the principal notions of general chemistry, which as we proceed we propose to apply. We must, however, before ending this chapter say a few words on what have been called catalyses. Certain bodies brought’ into contact with other bodies determine by their presence alone, and without taking any other part in the reactions, either combinations or metamorphoses or unfoldings. It. seems as if in these cases the body, intervening, by its presence alone, brings into play an attrac- tive force sufficient to disturb the atomicity of the body which it influences, without, however, being able to enter into combination with that body. For instance, platina determines, by its presence alone, the combination of oxygen and hydrogen, the formation of water; it transforms also alcohol into acetic acid by deter- mining its oxidation. These are catalyses of combination. The albuminoidal substances introduced into the stomach impregnate themselves there with gastric juice, expand, and in 1 Consult for further details, Wurtz, Philosophie Chimique, Chimie nouvelle, dc. Naquet, article, Atomique (Théorie) in the Encyclopédie Générale. CHAP. I. | CONSTITUTION OF MATTER. consequence the organic substance of the gastric juice achiev in these alimentary substances an isomeric modification, whic renders them liquid, absorbable, in short, transforms them in! albuminose. In the same way, under the influence of sulphur acid diluted, cane-sugar, cellulose, gums, and fecules are metamo phosed first of all into dextrine, and then into glycose, or grap sugar. These are isomeric catalyses. The hippuric acid of the urines of herbivorous anima unfolds itself, under the influence of the mucous elemen modified by the air, into hippuric acid and sugar of gelatine « glycocoll. That is an unfolded catalysis. In sum, the universe must be regarded as a whole compost of atoms dissimilar, and variously grouped according to the affinities. These active atoms are the foundation, the substanc the cause of all things: to use the expression of Tyndall, th are giants travestied. The various aspects of bodies result from the various mod of aggregation of the constituent elements. “« All the changes accomplished on the surface of the globe a due to combinations which are made or ‘to combinations whi are unmade.” + All chemical phenomena are consequently the expression atomic combinations, and can be included in four gener types : 1, Simple change of molecular structure, or isomeria. 2. Unfolding of compound molecules. 3. Adjunction, addition of atoms, or of molecules not y saturated, or, inversely, subtraction of atoms. 4. Substitution of certain atoms, certain molecules for othe in a compound body. These general characteristics manifestly exclude all ul mate, all radical difference between living organised bodies ai 1 Dumas, Traité de Chimie, t. viii. t 10 BIOLOGY. [Boox 1. inorganic bodies. Is there sufficient reason, however, for distin- guishing between an inorganic world and an organic world? What are the dissimilar qualities of these two grand groups? This is what we propose to examine in the following chapters. [Wote—When in this chapter atoms are spoken of as full, it is in the sense of a plenum excluding a vacuum,— TRANSLATOR. | CHAPTER II. _ANORGANIC SUBSTANCES AND ORGANIC SUBSTANCES, Ir, as results from the preceding exposition, the universe is a whole eternally unstable in form, eternally immutable in sub- stance, it follows as a matter of course that living or organised bodies cannot be constituted of aught essentially special. An integrant part of the medium which environs them, they come forth from it only to return to it, and there is not an atom of their substance which does not participate of the eternity of universal matter, the basis of everything which exists. There is not one of these atoms which has not played an infinite number of parts in an infinity of organic and anorganic com- binations, and which is not destined to play an infinite number more. Also, in analysing elementarily the most complex of animals, man, we, in normal conditions, find in him only four- . teen simple bodies of mineral chemistry, the list of which is herewith given :— Oxygen, ~- Phosphorus, Calcium, Hydrogen, Fluorye Magnesium, ~ Azote, Chlorine, Silicium, Carbon, Sodium, Tron. Sulphur, Potassium, Moreover it must be stated that the mass of the human body is especially constituted of four of these simple bodies, namely, _azote, carbon, hydrogen, oxygen. , 12 BIOLOGY. [Boox 1. If the results are accepted of elementary chemical analysis by decomposition, organised beings do not differ in substance from unorganised beings. But the analogy in substance does not exclude very important differences in form ; for we know that the properties of bodies are intimately related to their com- position, to the mode of aggregation of the substances which constitute them. Let us remark, in passing, that of the four simple bodies occupying the first place in the composition of the body of man and of the animals, there are two whose affinities of combination are neither strong nor numerous, and which have a certain degree of chemical inertia. Carbon, which is completely inert in ordinary temperatures, unites itself only to a small number of substances, and often by only a ‘feeble bond. Nevertheless it largely blends with the constitution of plants, and occupies a very important place in the constitution of animals. Azote, more indifferent still than carbon, is found in large quantities in the vegetal kingdom, in quantities still larger in the animal kingdom. It is this very inertia shared, though in a less degree by a third element, hydrogen, which renders these bodies suit- able to figure in the chemical constitution of living beings! In these beings, in effect, matter is in a state of extreme mobility ; it is subject to a perpetual movement of combination and decom- bination ; without repose, without truce, its elements go and come, have reciprocities of action, aggregate themselves, dis- ‘aggregate themselves ; there is a real whirl of atoms, in the very midst of- which fixed compounds, with chemical elements solidly cemented together, can only figure in a secondary fashion. Here are needed compounds unstable, of a great molecular mobility, capable of forming, disaggregating, metamorphosing, themselves, of renewing the woof of the living tissues. At the very outset the ternary compounds non-azotised, the aggregates of hydrogen, of oxygen, and of carbon, that is to say, the fixed oils, the fats, the gums, the starches, the resins, the sugars, and so on, the constituent principles of plants and 1 See H. Spencer, The Principles of Biology, vol. i. Cuap. 11.] ANORGANIC AND ORGANIC SUBSTANCES. 18 animals possess a great inertia and a notable instability ; often they are susceptible of isomeria (sugars, dextrine, and the like). As regards the more complex compounds, those in which carbon, hydrogen, azote, sulphur, phosphorus ally themselves to form the substances called albuminoidal, molecular instability is carried in them to the maximum ; the unfoldings, the isomeric modifications are effected with extreme facility. Further on we shall, in reference to nutrition and digestion, signalise the im- portant isomeric modifications which transform the insoluble albuminoidal aliments into soluble substances. Let us call atten- tion also, by the way, to the still more curious and typical metamorphoses which the various kinds of virus and miasma produce in the albuminoidal substances of living bodies. It deserves remark, besides, that these last substances, when once modified isomerically, possess the murderous property of trans- mitting by simple contact to sound organic substances the molecular alteration they have themselves undergone. But, finally, we may observe that these actions of contact are not peculiar to organic substances. They have, like the isomeric phenomena, their analogues in the chemistry called anorganical. In ‘effect there is no radical difference, no abruptly settled frontier between organic chemistry and inorganic chemistry. The two kinds of chemistry study the same elementary bodies which are subject to the same laws. Organic substances proceed from anorganic substances, and return to them incessantly, to come forth from them anew. For the most part we merely find in organic substances greater complexity and instability. Also we see modern chemistry striving more and more to pluck from living bodies the es of the fabrication of substances called organic. Moreover, if we fine in a graduated series the mineral and organic compounds, we discover between the two classes transitory groups, forming a point of union: these are the carburets of hydrogen, the alcohols, the ethers, ternary acids, fat bodies, the syn- thesis of which the chemist is now able to accomplish. Neither is there anything inalienable or special in the composition of organic 14 BIOLOGY. [Book 1. products. We can succeed in substituting magnesia for lime in the shells of eggs. We can, in fats, replace hydrogen by chlorine, without modifying essentially the properties of the compound. Chemical synthesis has also tried to reproduce the simplest of the azotic organic substances. There has been a direct repro- duction of urea, of taurine, of glycocoll in the laboratory ; and if the. true albuminoidal bodies have hitherto defied the efforts: of synthetic chemistry, we may almost with certainty predict that they will not defy them always. It will then be possible to appropriate direct from the mineral world fibring, albumings : caseing, and so on, that is to say, the special, the most needful aliments of man. This grand discovery must inaugurate for civilised communities a new era. It must be for man a real enfranchisement, by diminishing in a prodigious measure the sum of muscular labour, to which for more or less duration and progression he is now doomed. These preliminaries settled, we are able to enumerate the various groups of simple or compound substances, which by their union constitute the bodies of organised beings. M. Ch. Robin has given an excellent classification of these substances or ¢mme- diate principles.' According to him, the immediate principles are the ultimate solid bodies, liquid or gaseous, to which we can reduce the liquid or solid organised substance, the humours and the elements. But in order that these ultimate materials may merit the name of immediate principles, M. Robin thinks they must be obtained without chemical decomposition, by simple coagulations and successive crystallisations. These bodies, which, by their innermost blending, their reci- procal dissolution, constitute the semi- solid organised substance, can be grouped into three classes : 1. The first class comprehends the crystallisable or volatile bodies without decomposition, having a mineral origin and coming forth from the organism as they had entered it (water, certain salts, and so on). 2. The immediate principles of the second class are also 1 Charles Robin, Legons swr les Huwmewrs, Paris, 1867. Car. 11.] ANORGANIC AND ORGANIC SUBSTANCES. 15 crystallisable or volatile without decomposition, but they are found in the organism itself, and come forth from it direct as excre- mentitial bodies. They are acids, for instance, the acids tartaric, lactic, uric, citric ; vegetal and animal alkaloids: creatine, creati- nine, urea, caffeine, and so on; fat or resinous bodies; sugars of the liver, of grape, of milk, of cane, and the like. 3. In the third class of immediate principles we find bodies not crystallisable or coagulable. They are formed in the organism itself ; then, decomposed there, give birth to the imme- diate principles of the second class. The organic substances, properly so called, the substances of the third class, constitute the most important part of the body of organised beings (globu- line, musculine, fibrine, albumine, caseine, cellulose, starch, dextrine, gum, and some colouring matters, such as hematine, biliverdine.) Tt is from the intense union, molecule by molecule, of substances appertaining to .these three groups that organised substance results, formed of multiple elements, but constituted in great part of bodies complex, inert, unstable, easily decomposed, either through the play of chemical affinities, or the action of undula- tions calorific, luminous, electric. So far we have occupied ourselves with the materials of organised bodies only from the point of view of their chemical composition ; but it is quite as needful to take into consideration their physical state and physical properties. An English chemist, justly celebrated, Graham, fell on the happy idea of grouping all bodies, according to their characteristic physical state, into two grand classes, that of crystalloids and that of the colloids. The crystalloids comprehend all the bodies which ordinarily form solutions sapid and free from viscosity. These bodies have furthermore the property of traversing by diffusion porous partitions. The colloids have a consistency more or less gelatinous (gum, starch, tannin, gelatine, albumine). They diffuse themselves 1 Phil, Transactions, 1861, p. 188 ; Moigno, Physique Moléculaire. 16 BIOLOGY. [Boox r. feebly and slowly, as the following table indicates, which gives the time of equal diffusion for some bodies taken in the two classes :— : Chlorohydricacid . . . 2... » b Ghlorure of-sodium . ..... . . 238 Canesugar . . 2 2. ew ee ee 0 Sulphate of magnesia. . . . . . . . 7 Albumine . . 2... 1. ees 49 @aramel 20 we Ge we ee 9B Herefrom it is seen that chlorohydric acid traverses the porous membranes forty-nine times faster than albumine, and ninety-eight times faster than caramel. It is no doubt owing to this feeble diffusibility that the colloids are savourless when they are pure. Besides, these colloids do not comprehend merely the complex organic substances called albuminoids ; certain bodies indubitably mineral, such as silica, hydrated peroxide of iron, can assume the colloidal condition. Both the one and the other, moreover, enter into the composition of organised bodies. A particular soluble form of the hydrated peroxide of iron, which normally is an element of the blood, gives, when we dissolve it in water in the proportion of 1 to 100, a red liquid, condensing into coagulum, into a sort of rutilant clot, under the influence of traces of acids, of alkalies, of alkaline carbonates, and of neutral salts. Certain colloids, such as gelatine, gum arabic, are soluble in water ; certain others, such as gum tragacanth, are insoluble therein. In any case they have as a general characteristic the power of absorbing a great quantity of water, of augmenting enormously in volume, and of then losing this water very rapidly by evaporation. It seems as if in this case they are merely subject to a sort of capillary imbibition. Yet it must be admitted that they incorporate more intensely with themselves a certain quantity of water as an integrant portion. Hence it appears that there is for colloids a water of gelatinisation, as there is for crystals a water of crystallisation. cHaP. 11.] ANORGANIC AND ORGANIC SUBSTANCES., 17 ° . v There is not, however, any absolute incompatibility between colloids and erystalloids. If the colloids are for the most part complex organic compositions, we have seen above that very simple mineral compounds can assume the colloidal state ; and on the other hand Reichert discovered in 1849 that albuminoidal] substances can take the crystalloidal form. We shall be able to cite examples of. this last case when speaking of plants. In almost all seeds, in effect, we find a white powder, finely grained, and presenting sometimes crystallised facets, square edged. The diameter of these particles is from 0",00125 to 0™,0375. They are called particles of aleurone. They are composed of fibrine, of albumine, of legumine, of gliadine, of gum, of sugar, and so.on. They are aliments in reserve. ‘hese albuminoidal crystalloids are birefringent ; they are all insoluble and unassailable in water afid alcohol. We have signalised above the strong diffusibility of the crys. talloids; it is so great that they can penetrate the colloids, blend with them as intensely as with water, while on the con. trary the colloids can scarcely diffuse themselves into effective union with each other. From this enormous difference of diffusibility between colloids and crystalloids it results that, if we separate by a porous mem. brane water and a colloid holding in solution a crystalloid, this last disengages itself from the colloid and traverses the mem. brane to dissolve in the water. It is thus that we can very easily with a membrane dialyser extract from a colloidal substance arsenious acid, digitaline, and so on. This process is made use of in certain toxicological researches, and also industrially to purify gums, albumine, caramel, and the like. The reader has no doubt already the presentiment of the weight and worth of some preceding statements for the compre hension of biological facts. In effect every organised being is a compound of colloidal bodies holding in solution crystalloidal bodies. But this organised body is in a state of perpetual reno- 1 Duchartre, Botanique, p. 69 ; Sachs, Traité de Botanique, p. 72. ‘3 18 BIOLOGY. [BOOK I. vation. Unceasingly it plays, face to face with the exterior medium, the part of dialyser, either directly or by the aid of special apparatus. It forms nutritive soluble substances, and rejects waste substances, likewise soluble, at least in the liquids of the organism. When, for instance, the residuum of the waste of the living tissues is composed of erystalloid bodies, these bodies can easily and. rapidly traverse the colloidal substance of the tissues to be expelled from the organism ; but their expulsion leaves in those same tissues a void which other soluble substances can come to ill by permeability ; and in this fashion the losses undergone by the living machine are repaired without difficulty. Finally, the colloidal state is the form the most suitable for the manifestation of the instability, the molecular mobility of the complex bodies which constitute organised beings. Under this form they are really in the dynamical state; they yield without difficulty to the shock, to the action of incident bodies. They can unmake and remake themselves, become the scene of a perpetual exchange of molecules and of atoms, in a word, of a vital progression and regression. CHAPTER III. CHEMICAL COMPOSITION OF ANIMALS AND PLANTS. Is the two living kingdoms, organised substance is, as we have already seen, constituted by three groups of bodies inti- mately blended, and which Chevreul’ was the first to call immediate principles. It is now needful to compare with each other the chemical species which enter into the composition of the plant and into that of the animal. We shall glance very rapidly at the immediate principles of the first category. In effect, water, which constitutes in weight the largest part of organised beings, mineral salts, atmospheric gases, are manifestly unable to furnish to us sufficiently distinctive characteristics. But’ that the results of the comparison may be the more striking we shall indicate first of all in bold outline what is the chemical composition of plants, and what is that of animals. = : 1. Chemical Composition of Plants. Organised vegetal tissues, when submitted to desiccation, present a friable residuum, the weight of which is very variable. In the average of terrestrial plants this residuum is from a fifth to a third of the total weight ; but it rises to eight-ninths if we take ripe seeds, and can descend to a tenth or a twentieth in aquatic plants and certain mushrooms., This residuum, desiccated, offers always to chemical analysis, carbon, hydrogen, oxygen, azote and sulphur, potassium, calcium, magnesium, iron, phosphorus. Often, moreover, we find therein sodium, lithium, Ge ao 20 BIOLOGY. [BOOK I. manganese, silicium, chlore. Finally, in the marine plants we discover iodine and brome. Such are the ultimate results of analysis; but, of course, during life, these bodies are not, for the most part, in a state of liberty ; they are combined in various manners. The metals are usually in the state of salts, of sulphates, of phosphates, of carbonates, of oxalates, and so on. There is also a certain quantity of oxygen, of azote, of hydrogen and of carbonic acid dissolved in the liquids or impregnating the vegetal anatomical elemerits. But the true organic compounds are ternary or quaternary compounds. The ternary compounds are formed of carbon, of hydrogen, and of oxygen. They constitute the strongest | part of the vegetal texture. Let us mention first of all cellulose, which forms almost alone the primary part of the vegetal cells, and then many substances which are isomeric to it, such as in- uline and xylogen. The first of these isomers of cellulose, inuline, is found in decomposed roots, in colchicum bulbs, in dahlia tubers, and so on. As to xylogen, it is the substance which gives rigidity to ligneous tissues. Furthermore, in putting ourselves at the point of view of chemical composition we have to see the relation of cellulose to the starches, the sugars and the gums. To the type of sugars, the sugar of grape, or glycose, has long been given the formula C"H”0",2HO. Starch is composed of C”H'°0*,HO. In reality, these ternary bodies have already in a large measure the characteristics of complexity and instability. peculiar to organic substances, and their definitive formula is still a subject of discord among chemists, According to M. Wurtz, for instance, the formula of cellulose would be C°H™0%, that of gum arabic C"H”O", that of starch C H™0*, and this formula would not vary by the isomeric transformation of starch into dextrine. Saccharine and amylaceous matters bear as chemical characteristic the inclusion of hydrogen and oxygen in such proportions that the oxygen could suffice exactly to saturate the hydrogen and to transform it into water. The general formula of these groups would therefore be C™(H?0),1 i . Wurtz, Chimie Nouvelle, CHAP, 111.] COMPOSITION OF ANIMALS AND PLANTS. 21 To complete the enumeration of the ternary vegetal compounds, we have to mention the fat vegetal bodies, the non-azotised oils, which are also compounds.in complex molecules of carbon, of oxygen, and of hydrogen. After the group of ternary organic substances comes a tribe of azotised compounds, wrongly, and in virtue of questionable - chemical theories, called quaternary bodies. The molecules of these last bodies are, it is true, formed for the most part by atoms of carbon, of oxygen, of hydrogen, and of azote; but almost constantly a certain quantity of sulphur and of phosphorus must be joined to them. These quaternary compounds are the organic substances by excellence ; we seek in vain their analogues in the mineral world. They form themselves spontaneously in the texture of living beings; whereas the ternary compounds spoken of above can be brought into relation with the carburets of hydrogen which connect them with the inorganic world. The azotised vegetal substances form two principal groups,— the group of the alkaloids, and that of the albuminoids. The alkaloids are very complex compounds, capable of combining as bases withan acid. These bodies, unimportant as to quantity, are very important as to their physiological or toxical properties ; they are quinine, strychnine, morphine, and so on. But the substances which, without question, hold the first rank, the compounds essential to vegetal life as well as to animal life, are those which form the group of the albuminoids. We shall see that these substances constitute the nucleus of the vegetal cells, constitute their internal membrane, that they are also found in the liquid filling the cells, in the protoplasm. Among the most important of these substances we must name gluten or vegetal fibrine, so abundant in the seeds of the cereals. To it is given as formula, according to the theory of Miilder, 10(C*H?0lAw) + 8. In relation to gluten we have to view glutine, an analogous -albuminoidal substance; it is the coagulable principle of the sap of plants. It is likewise called vegetal albumine. 22 BIOLOGY. [Book I. Finally there is extracted from the seeds of the leguminous plants a third albuminoidal substance, containing, like gluten, sulphur, and which is called vegetal caseine. The last substance which we have to mention is the green matter of plants, chlorophyll. Its physiological agency is ex- tremely curious and interesting ; we shall therefore describe it in detail in the course of our expositions. Here it suffices to observe that chlorophyll cannot be placed in the group of the preceding substances, called proteical. Neither phosphorus nor sulphur is found therein. It is composed only of carbon, of hydrogen, of oxygen, of azote, and, what is altogether character- istic, of iron. Its formula, still however requiring consideration, would be C!8H°AzOS + Fe (in indeterminate quantity). 2. Chemical Composition of Animals. In a preceding chapter we have enumerated the fourteen simple bodies entering into the composition of the most complex of organisms, the human organism. A glance thrown at this list suffices to show that if the elementary composition is held in view, and the quality of the elements is alone considered, there is almost identity between the vegetal organisms and the animal organisms. But in both kinds of organism these elementary bodies are aggregated in various combinations, with the exception of azote and oxygen, of which a part is in a state of liberty alike in the animal and the vegetal organisms. In every animal organism also we encounter, in a state of intense blending, immediate principles of the three classes. The immediate principles of the first class, or mineral principles, penetrate, entirely formed, into the animal economy ; and entirely furmed they come forth from it: this is the case with water, azote, certain salts, and so on. . The principles of the second class are in general hydrocar- bonised. ternary compounds such as lactic acid and the lactates, cHaP. 111.] COMPOSITION OF ANIMALS AND PLANTS. 23 uric acid and the urates, fat bodies (oleine, margarine, stearine), animal starch or glycogenous matter of the liver, the glycose of the same gland, chitine. They comprehend quaternary azotised pro- ducts, the result of the disassimilation of the organic elements, such as urea (C2A@°H‘0"), creatine (C°H®A@?0‘), creatinine (C®°H7Az30"), cholesterine (0°H#O?), and so on. While the principles of the first class pass merely’into the organism by coming from the exterior world, those of the second form them- selves in the animal organism, but do not sojourn there. The immediate principles of the third class are numerous neither in ‘animals nor plants, but they play in the first a more important part than in the last. They are the albuminoidal sub- stances, all likewise colloids, and insatiable in their thirst for water. These bodies are very unstable compounds, much inclined to isomeric modifications. They are formed in the animal economy, never leave it when it is in a healthy state, are renewed therein molecule by molecule through the nutritive movement, and from their quantity and from the dominant part they play, they constitute the very essence of the living organism. Their formula, as we have already stated, is still undecided. There has been a disposition to consider them as all formed of the same radical, proteine, united to atoms of sulphur and phosphorus. In boiling the epidermic productions, the cartilages, the organic framework of the bones, the cellular tissue, the tendons, and so on, we obtain quaternary azotised substances, chondrine, gelatine, containing .less carbon and more azote than the other albuminoidal substances: moreover, containing no sulphur. The most important animal albuminoidal substances are fibring, albumin¢, caseing, the analogues of which we have signal- ised in plants, In the same way that in plants we have found a spectal quaternary substance, chlorophyll, containing a metal, iron, we find also in the superior animals a matter analogous to albuming, but coagulating much less easily when itis dissolved in water. This matter is the substance of the globules of the blood, globuling, Like chlorophyll, it contains iron in its com- 24 BIOLOGY. [BooK I. position, and, like it, also exerts a cuales action on one of the gases of the atmosphere. How summary soever may be ‘is short enumeration which precedes, it suffices to establish from a thorough knowledge of the matter a parallel between the composition of animals and that of plants, and to give saliency to the analogues and the differences. a 3. Lhe Organic Substances of the two Kingdoms. A supreme fact is evolved from the preceding examination, namely, that there is in the ternary and quaternary substances a dominant element common to them all, carbon. Of all organic substance, carbon is the base. In weight it forms the principal element thereof. The albuming of the blood contains about fifty per cent. of carbon. But in organic substances carbon plays a much more important part still. It isthe bond of all the various atoms, which compose the complex molecules of organised bodies. We have already seen that carbon is a tetratomic body, that is to say, capable of fixing, of keeping wedded to one of its atoms four atoms of a monoatomic body, such as hydrogen, or two atoms of a diatomic body, such as oxygen ; and soon. Wehave besides remarked that the atoms of carbon could unite with each other in neutralising reciprocally one only of their affinities, the others remaining free and fit to satisfy themselves, in attracting and fixing either atoms of other elements or even aggregates more or less complex, radicals comporting themselves as a single atom. But these atoms, these radicals, are often only aggre- gated to the atom of carbon which attracts them by one of their atlinities, while the others remain active, exciting the aggrega- tion of new atoms. Let us take, for instance, the iodide of methyl, that is to say, of carbonised hydrogen, an atom of iodine taking the place of an atom of hydrogen :— H | H—-C—I | A CHAP. It1.] COMPOSITION OF ANIMALS AND PLANTS. 25 Heating in suitable conditions this body with potash or hydrate of potassium, we determine the displacement of the atom of iode, which combines with the potassium and is suc- ceeded by the oxygen of the potash. But this oxygen is di- atomic: the half only of its affinity is satisfied or neutralised by this displacement: the rest still remains free. This is why, without ceasing to form part of the carburet, the atom of oxygen unites itself on its own account with a molecule of hydrogen likewise taken from the hydrate of potassium, and we have thus wood spirit : H | H—C—(0H) | # H We have taken as example a body in which one atom only of carbon figures. But if we represent to ourselves a poly-car- bonised compound we at once see to what a degree of complexity and mobility such a body can attain ; therefrom we gain a general idea of what the chemistry of organic bodies is; we recognise that modern chemists have the right to call this branch of their science the chemistry of the compounds of carbon; and we willingly subscribe to this proposition of Haeckel: “It is only in the special chemico-physical properties of carbon, and especially in the semi-fluidity and instability of the carbonised albuminoidal compounds, that we must seek the mechanical causes of the phenomena of particular movements by which organisms and inorganisms are differentiated, and which is called in a more restricted sense Life,” * The general statements given above apply equally to organic vegetal substances, and to organic animal substances, forasmuch as we have seen that as regards quality, as regards general 1 E, Haeckel, Histoire de la Création Naturelle. Paris, 1874. 26 BIOLOGY. [BOOK I. chemical composition, the two classes of substances are manifestly identical. Consequently, there is no radical difference between the organic substances of the vegetal kingdom and those of the animal world. Nevertheless these are notable dissimilarities ; they bear on the relative quantity of the ternary compounds non-azotised, and the quaternary compounds azotised, in both the realms of Nature. In effect, the albuminoidal substances which constitute the chief part of any veritable animal organism are from the quantitative point of view little more than accessories. The great mass of every true plant is especially constituted by the non-azotised carburetted substances. Azote, though forming an essential element of the intracellular vegetal protaplasm and of the alkaloids, represents often in weight less than a hundredth of the dry matters: rarely the proportion rises to three hundredths. ‘To sum up, the vegetal kingdom ‘is, quantitatively considered, the kingdom of ternary carburetted substances, while the animal kingdom is that of carburetited substances. azotised or quaternary. Consequently there is in the animal world a greater degree of chemical complexity and instability, that is to say, a superior vital activity. Nevertheless, there is no radical difference. We must hence- forth reject that idea of complete antagonism between the two kingdoms, which has so long prevailed in science. We must no longer consider every plant as an apparatus of reduction specially charged to form, all in a lump, at the expense of the mineral world, ternary and quaternary compounds for the nourishment of animals. "We must cease to see in every animal an apparatus of -combustion whose mission is to destroy those compounds with- out being able to form any. Cl. Bernard has demonstrated that the cells of the liver fabricate at the expense of the blood an amylaceous matter possessing, according to the analysis of M. Pelouze, the same composition as vegetal starch, and, like it, transforming itself into sugar. Finally, M. Rouget has found this amylaceous matter, glycogen or zooamyline, in the muscular tissue, in the lung, in the cells of the liver, in the placenta, in cHaAP, 11.) COMPOSITION OF ANIMALS AND PLANTS. 27 the amniotic cells, the epithelial cells, the cartilages, &e., of the vertebrates.1 Fora long time cellulose was considered a substance exclusively vegetal ; but after a while, under the name of chztind, or tunicind, it was found in the tegumentary envelope of the tunicates, in the exterior skeleton of the anthropods, and so on; and M. Ber- thelot has succeeded in transforming into sugar this tunicing, this animal cellulose, for ebullition and acids metamorphose it into glycose.? : Even chlorophyll, that vegetal substance frpoxcsllanes has been found in certain rudimentary animals, Therefore, once more we declare that there is no radical difference, no chasm between the two living kingdoms, from the point of view of the composition and formation of the organic substances, In this respect there is no reason why the two kingdoms should not be included under the denomina- tion of Organic Empire, as Blainville proposed. Nore.—Both as w substantive and as an adjective, vegetal is a good old English word which is often for obvious reasons preferable to: vegetable or plant.—Translator. 1 J. Gasarrat, Phénoménes Physiques dela Vie, p. 196. 2 J. Gasarrat, loc. cit. CHAPTER IV. OF LIFE. Lirg has long been the mystery of mysteries; and in modern times it has been the last refuge, the citadel of supernaturalism. In fact, so long as there were no clear ideas regarding the con- stitution of bodies, or the composition of chemical aggregates, so long as so-called organic substances appeared radically different from mineral substances, it was impossible to unravel the mystery of life. We now know that organised bodies do not contain a material atom which was not first derived from, and afterwards restored to, the exterior medium. We have made an enumeration of the immediate principles which constitute living bodies; we have been able to reproduce a certain number of these in our chemical laboratories. We know in what physical state, under what blended conditions, they are found within organised and living bodies. We know, moreover, that the entire universe contains an always active matter, that what is called force cannot sever itself from what is called matter, that consequently there can no longer be any question of a vital principle, of an archeus, superadded to living beings, and regulating their phenomena. Even these simple general facts authorise us to affirm that ital phenomena are simply the result of the properties of living matter. To give a just idea of life, it remains to us then to determine what are its properties, and also what are the principal conditions of their manifestation. We prove then, first of all, that life depends strictly upon the exterior medium, that an alteration in the composition of the OHaP. IV.] OF LIFE, 29 aérian or aquatic medium determines the cessation or suspension of the vital movement. We can even at will suspend and reanimate life in certain organised beings. M. Vilmorin succeeded in reviving, by means -of moisture, a dried fern sent from America. By drying and then moistening certain infusoria we may arrest and revive the course of life in them. In America and Northern Russia frozen fishes, brought from great distances, are revivified by being plunged into water of the ordinary temperature. : In Iceland, in 1828-9, Gaymard in ten minutes revivified frozen toads in tepid water. ; In the case of dried organisms, the organic substances have been deprived, by evaporation, of their water of gelatinisation, and thereby of their molecular mobility, the instability indis- pensable to the realisation of atomic changes ; in fact, they have been separated from the exterior world, yet without decompo- sition ; whence their easy revival. In congealing organisms, an analogous result is obtained. By the solidification of water substances lose their colloidal state. They are, in some degree, chemically paralysed, but can never- theless revive, if congelation has produced neither chemical decomposition of the substances, nor morphological destruction of the tissues and of their anatomical elements. These facts suffice by themselves to prove that the principal - condition of life is the interchange of materials between the living body and the exterior world; but, fortunately, we are not limited to such éommonplace demonstrations. Vital activities have been minutely scrutinised, watched, and followed step by step, as we shall see further on. We have been enabled to note the incessant amalgamation with the organism of substances derived from the exterior world, to observe the modifications and transformations which these substances undergo and promote in the midst of living matter; the results of all these biological operations have been summed up, and establish approximately the balance of gain and loss. In short, it is now known that 300 BIOLOGY. [BOOK 1. the principal vital phenomenon, that which serves as a support to all the others, is a double movement of assimilation and of dis- assimilation, of renovation and of destruction, in the midst of living matter; that this matter may be either in a semi-solid state, and without structure, as in certain inferior organisms; or that it may be in a liquid state more or less viscous, like the blood and lymph of the superior animals; or finally, that it may be modelled into anatomical elements, into cells and fibres bathed with liquids and gases, as in the bodies of all the superior animal and vegetal organisms. The living substance is thus a chemical laboratory in constant action. It is the physical or chemical properties of this sub- stance, diversely modified, which underlie all the vital properties, nutrition, growth, reproduction, the chlorophyllian attribute, motility, and innervation. % Now the six properties which we have just enumerated are the six principal modes of living activity, the six categories under which all biological phenomena group and class them- selves. The chlorophyllian property is almost exclusively vegetal ; but the five other fundamental properties represent, when united, the highest, the most complete expression of life. But they are far from being always united ; they are also far from having the same importance. Some of them are primordial, some secondary. The most important of all is evidently nutrition, the double and perpetual movement of molecular renovation of the living substance. Without nutrition there can be no growth, no repro- duction, no movement, no conscious sensitiveness, no thought. , Tn truth, life can be conceived of as reduced to its most simple expression, to mere nutrition. A being capable of nourishing itself, and destitute of every other property or function, lives still; but if it has not the faculty of reproduction, which, as we shall see, is only a simple extension of the nutritive property, its life will be only an individual life; a moment will come when the nutritive exchanges will slacken, when the nutritive residue, incompletely expulsed, will impregnate the living tissues CHAR. Iv.] OF LIFE. 31 and liquids, obstructing them, so to speak; then the colloidal plasmatic substances will cease to restore themselves, to regene- rate themselves. Soon the retardment will end in complete arrest; then the organised being will have ceased to live; the complex elements which composed it will change, will break asunder, and the groups of their molecules and of their atoms will re-enter the exterior medium, the mineral world. If, on the contrary, the. nutritive property of a living being is sufficiently energetic to rise, as it were, to excess, even to growth and reproduction, the being is sure of living in its offspring ; it fills its place in the innumerable crowd of living beings, and can even, if the doctrine of evolution is as true as it is probable, become the source of a superior organised type, can ascend in the hierarchy of life. In fact, many of the inferior organisms are endowed only with the properties of nutrition, growth, and ‘reproduction, At a greater degree of complication and perfection a new property appears, motility, subordinated likewise to nutrition, when it concerns the individual, to reproduction when it concerns the series. No one is ignorant that large numbers of animals are endowed solely with these four properties, nutrition, growth, reproduction, and motility, which are possessed by a number of plants also, as we shall see hereafter. Nutrition, growth, and reproduction are truly fundamental properties. They belong to the entire organic world, to every- thing which lives and lasts. Above these properties must rank three others, all naturally subordinate to the primordial property, nutrition. These three are, the chlorophyllian property, motility, and innervation. The chlorophyllian property is, with rare exceptions, confined to plants. Motility is, in a measure, common to animals and vegetals, . Finally, the last vital property, innervation, is limited to the superior animals. It is also the most delicate, the most subordinated to, the most closely connected with, the integrity of nutrition, the most dependent, directly or indirectly, upon the 32 BIOLOGY. [Boox 1. other vital properties. Let but the nutritive liquids impregnated with oxygen cease to reach the nervous cells, to’ bathe them, to excite them, to renew them, immediately motility, sensibility, and. thought vanish; the animal re-descends, for a time, or for ever, to the level of unconscious organised beings. From this physico-chemical point of view we can now, without much difficulty, form an idea of the totality of the molecular movements which form the essential basis of life. Every living being is constituted, in a general manner, of colloidal substances more or less fluid, more or less solid, holding in solution salts, gases, and soon. A portion of these salts and gases hag been introduced from without, and is ready to combine itself with the unstable colloidal substances; some are the result of combina- tions already effected; but this process of combination and separation cannot stop; for the atoms of atmospheric oxygen mingle themselves cedsélessly with the organic molecules, separate them, disaggregate them by virtue of their powerful affinities ‘for certain elements which form part of their complex molecules. After a time more or less short, the oxygen, by a slow oxydation, would have thus destroyed the living substance, if food had not likewise been introduced from without into the texture of the AMiying being. These renovating substances, after having often * undergone preparatory chemical changes, after having become nutroments, that is to say, after having acquired a chemical com- position and a physical state which assimilate them to the living substance, identify themselves with it. _ One by one their mole- cules take the place of those which have been destroyed. The sliving being, thus incessantly restored, lasts, continues to live, and would live indefinitely, if this molecular movement never slackened. But we now know, through the magnificent generalisations of modern chemistry and physics, that in the world there are only , atoms in some degree animated, that these atoms transmit to each other mutually the movement which impels them, or which they engender. and that this movement, without ever being annihi- Cuap. lv. ] OF LIFE. 33 lated, transforms itself in a thousand ways. These transmuta-, tions of movement take place also naturally in living beings,/ and the impulsions, so complex and varied, of the molecules | transmit themselves to the different organic apparatus, producing, here the generation of new anatomical elements, there, the movements of totality of the living substance, elsewhere the nervous . phenomena of consciousness, everywhere a certain elevation of temperature and, doubtless, electric phenomena. It has been said, and may be admitted as a general principle, that the animal world lives at the expense of the stores of matter and of movement accumulated by the vegetal world. We shall have to show, at a future time, what amount of truth there is in this generalisation. We content ourselves, at present, with remarking that these vegetal accumulations are formed under the influence of solar radiation, that is to say, of the vibrations radiated by the central star of our planetary system, and that, consequently, the dynamic solar source is the great reservoir of force, the great motive power, which gives the impulse to the vital movement, and sustains the impulse given. And now can we define life? For that purpose it will evi- dently be sufficient if we summarise the preceding facts into as clear, and at the same time as brief, 2 formula as possible ; for it is not our intention to pass in review the very numerous definitions which have been given of life, long before its pheno- mena were scientifically analysed. The definition now most commonly adopted in France is that given by Blainville : “Life is a twofold movement, at once general and continuous, of composition and decomposition.” This defini- tion, as H. Spencer judiciously points out,! is at the same time too comprehensive, and not comprehensive enough. It is too comprehensive, because it is applicable to that which occurs in an electric pile or in the flame of a wax taper, as well as in the primordial nutritive phenomena; it is too restricted, because it leaves out the highest, the most delicate vital activities, the 1 Principles of Biology, vol. i. D 84 BIOLOGY. [Boox 1. cerebral or psychical activities. Lewes says : “‘ Life isa series of definite and successive changes of structure and of composition, which act upon an individual without destroying his identity.” In speaking of structure, this definition excludes the activities of purely mineral chemistry, which the first does not, but it also forgets the cerebral activities, and besides it does not embrace the vital acts that take place in the plasmatic liquids, such as the blood, the lymph, which, though destitute of structure, are endowed with life, as we shall presently see. The definition of H. Spencer, ‘The continual agreement. between interior and exterior relations,” has the fault of being too abstract, and of soaring so high above facts, that it ceases to recall them. Besides, just by reason of its vague generality, it might also be applied to certain continuous chemical phenomena. It would be better to descend nearer to the earth, and to limit ourselves to giving a short summary of the principal vital facts which have been observed. Doubtless life depends upon a two- fold movement of decomposition and renovation, simultaneous and continuous ; but this movement produces itself in the midst of substances having a physical state, and most frequently a morpho- logical state quite peculiar to them. Finally, this movement brings into play diverse functions in relation with this morpho- logical state of the living tissues, habitually composed of cells and fibres endowed with special properties. Let us say then that “life is a twofold movement of simul- taneous and continual composition and decomposition, in the midst of plasmatic substances, or of figurate anatomical elements, which, under the influence of this in-dwelling movement, perform their functions in conformity to their structure.” CHAPTER V. ANATOMICAL CONSTITUTION OF ORGANISED BODIES. EVERYWHERE and always, as we have already expounded, the living or organised bodies are constituted by complex substances, in part albuminoidal, and in that special physical state which is called colloidal, The fundamental matter of these living bodies is uncrystallisable. ‘To live and to crystallise,” says Ch. Robin, “are two properties which are never united” (Kléments Ana- tomiques, p. 17). It is enough in effect for a body to be endowed with the humblest of vital properties, nutrition, not to be erystallisable. At the same time living substances are im- pregnated with crystalloidal solutions and with gases: this is a general attribute; but in the form this attribute is extremely diversified. At the lowest degrees of the organic world we find beings without structure, amorphous: for instance, the genus Ameba and the genus Monas; they are small contractile albu- minoidal masses whose form is modified incessantly. Such are also the simplest rhizopods, living masses rather more con- siderable, but without definite form; we see them emitting and reabsorbing tentaculiform prolongations of varying length. But if even in a small degree we study by the help of the microscope the structure of beings more elevated in the living hierarchy, we instantly see that the fundamental mass has lost its homogeneous- ness, that it has fractionised itself into corpuscles generally invisible to the naked eye. These small bodies, these living bricks which by their aggregation constitute every organic edifice a little complex, have been called anatomical elements or histological elements. D2 36 BIOLOGY. [Boox 1. Finally, these anatomical elements float more or less directly in living liquids, which are called blastemas, For instance, the freshwater polypus, celebrated on account of the curious experi- ments of regeneration to which it has given occasion, is solely eomposed of corpuscles living, spherical, of cells swimming in an intercellular liquid, which is a blastema. Thisis also the texture of certain infusoria, for example, of the Paramecia, and likewise of a number of plants. : Besides in plants, and especially in superior animals, exist systems of canals serving for the circulation of liquids as living as the figurate anatomical elements. These liquids, which, like the blastemas, to distinguish them from which there has been a wrong attempt, are both receptacles of disassimilated products and reservoirs of assimilable products, have been called plasmatic liquids, or plasmas. We have successively to describe living substance under the two general forms which it assumes, namely, the histological form and the blastematic and plasmatic form. 1. Of the Figurate Elements in General. The science of the figurate elements of living bodies, whose real origin only remounts to the end of the last century, has long borne the name of General Anatomy. It was not till 1819 that Mayer published a treatise of General Anatomy under the title of Treatise on Histology, and a New Division of the Body of Man. The word Histology has had eager, acceptance, no doubt because it is derived from the Greek, and it is now in general use. The first elementary histological form which organised matter assumes is the cellular form. We must understand by cell a microscopical corpuscle, having a sort of independence, an indi- vidual life, assimilating and disassimilating on its own account. The cell has generally a form more or less spherical. It is consti- tuted by a substance more or less soft. When it is complete it Cuar. v.] CONSTITUTION OF ORGANISED BODIES. 37 contains another cellular element which is smaller, a nucleus in which the living activity of the cell usually attains its maximum of power. Moreover, it often happens, especially in plants, that the exterior surface of the cellular corpuscle hardens. This hardened. surface then constitutes what is called the cellular membrane, The observations and the inductions of paleontology, of em- bryology, of the systematic natural history of organised beings, authorise us in considering the organic cell as the corner-stone of the living world, the common mother of all other histological elements. In effect the first figurate living beings have been monocellular, or composed of cells resembling each other, and simply juxtaposed. At the origin of nearly the whole of living beings, animals or plants, we find a simple cell. Finally, when we hierarchically class the innumerable organised beings which people our globe, we encounter, at the lowest, the humblest degree, beings composed of a single cell, or of a small number of identical and juxtaposed cells. The cellular theory which we have just in summary fashion sketched, is one of the grandest views of Biology. Bichat was the first to attempt the anatomical analysis of living beings, by trying to resolve each organised being into tissues anatomically and physiologically special. Schwann, carrying analysis further, decomposed the tissues themselves into microscopical elements, and was the first to formulate the cellular theory in his work entitled Microscopical Researches on the Conformity of Structure and of Growth of Animals and Plants. 1838.4 The cellular theory contested at present, or rather differently interpreted on certain points by M. Ch. Robin and his school, nevertheless keeps its ground as a whole. It is not easy to ~ understand without it the genesis and, the evolution of organised beings. Finally, this theory has led Physiology to scrutinise 1 Mikroskopische Untersuchungen tiber die Ubereinstimmung in der Struktur und dem Wachsthum der Thiere und Pflanzen.—De Mirbel had already shown that the tissue of planty is composed of utricles and cells. 1831-1832. 38 BIOLOGY. [Boox 1. more profoundly the mechanism of the vital acts ; it has taught it to refer them to their ultimate agents, that is, to the histo- logical elements themselves, which vary in function and in form in complex beings, and which we must consider as playing a part in the mechanism of organised beings, analogous to that of atoms in chemical aggregates. As Schwann has said, ‘“‘ Forasmuch as the primary elementary forms of all organisms are cells, the fundamental force of all organisms reduces itself to the fundamental force of cells.” (Mikroskopische Untersuchungen, 1838.) The cell, properly so called, of which we have given above a succinct description, is a sort of schematic type, scarcely existing in anything except rudimentary beings and tissues. If we study the cell either as a complex organism, or in the hierarchical series of organisms, we see it in effect modifying itself, putting on different forms when assuming diversified functions. Finally, another type of histological element appears: it is the fibre, a microscopical element likewise, springing evidently from the cell in certain cases, where the cells have merely been elongated by juxtaposing and cementing themselves end to end. These deri- vative fibres exist manifestly in plants, in which they often hollow a passage for themselves as canals. According to Ch. Robin, there is a different process in animals. Here the fibres, with all their essential attributes, would seem to be present at the very dawn of the embryonic life, forming themselves spon- taneously by genesis, at the expense of the blastematic liquids secreted by cells. As there are various species of cells, there are also various species of fibres ; but the true typical fibres, well specialised, are found scarcely anywhere except in the animal king- dom. We purpose speaking further on at greater length of cer- tain species of fibres, muscular fibres, nervous fibres, and so on. In sum, passing by some amorphous organised types, points of union of a sort between the living world and the non-organised world, we must consider every complex organism as being con- stituted’ by a great number of individuals, living, microscopic, Cuap. v.}] CONSTITUTION OF ORGANISED BODIES. 39 having each special activity and special functions. These ana- tomical elements are conformed in accordance with a small number of types, and in the superior organised beings they are grouped in tribes, and thus form tisswes, charged each to fulfil such and such great physiological function, which is the total of all the elementary activities (muscular tissue, nervous tissue, osseous tissue, chlorophyllian tissue of plants). As a matter of course the degree of differentiation in plants is very variable. It is an organic law that this differentiation of the anatomical elements is carried the further the more the organised individual is perfect. In other words, the great law of the division of labour reigns everywhere in the organised world. Besides, the elements themselves have a more complicated structure the more their function is complex (muscular fibre, nervous fibre), Finally, the more the organisation of ananimal, taken as a whole, is simple, the simpler is also the structure of each of the orders of anatomical elements. Thus the muscular fibres of the radiata, the annulata, the mollusca, the nervous tubes, the ganglionic cells of lampreys, are simpler than the same elements in the crab.} But in every superior organism there is a differentiated blend- ing of anatomical elements, having varied functions and varied degrees of structure. We could therefore, in every individual, group the elements in series, according to their degree of perfec- tion, of complication, and we should have a complete scale going from the elements, confused and even amorphous, of the inferior beings up to the elements with complex structure of the superior beings.” At the foot of the organic scale we find monocellular infusoria (polytoma, difflugia, enchelys, monas, ameba) formed of a single homogeneous substance. Some of them are constituted of a sub- 1 Ch. Robin, Aéments Anatomiques. * Ch, Bernard, Rapport sur les proyrés et la marche de la physiologic générale en France. Paris, 1867. 40 BIOLOGY. [Boox 1. stance slowly contractile, which seems to be the rudiment, still undivided, of the muscular fibre; it is a sort of non-figurate muscular matter. This matter is called sarcode. There seems to be in inferior beings a confusion of organic materials and functions. Many of the infusoria are endowed with motility and sensibility, with a sort of instinct, and yet they are destitute of muscular elements and nervous elements. We can place in a degree immediately superior the plants and the animals simply polycellular, that is to say, constituted of a certain number of cells similar to each other and grouped. They are beings formed of a single tissue. On the other hand, at the outset of their embryological exist- ence, the beings the most complex, the superior animals, man not excepted, commence by being monocellular, then pass through the polycellular state, the most rudimentary ; finally, in a last period, their histological elements differentiate. This gradual histological differentiation, which is observed in the embryological development of superior beings, can also be demonstrated in the paleontological succession of the organised beings on our globe. In fine, it is easy to encounter it anew by grouping living beings hierarchically, from the simplest to the most complex. ‘It is in this triple coincidence that the grand doctrine of evolution, founded by Lamarck and Darwin, finds its most brilliant confirmation. In the animal kingdom the figurate elements can be classed in two great groups: the group of the constituent elements, which forms the basis, the framework of every organised being, and that of the produced elements, which plays a part more or less secondary, and has an existence more or less provisional. It has been ob- served that the constituent elements were generally situated in the interior of the body, and the produced elements on the surface. But this division, to which M. Charles Robin first of all, and Mr. H. Spencer afterwards, accorded a supreme importance, is only, like most classifications, a commodious arrangement for grouping the elements. If it were literally accepted—and indeed it is so Cua. v.] CONSTITUTION OF ORGANISED BODIES. 41 accepted by M. C. Robin—it would be necessary to class among the constituent elements the globules suspended in the blood, the haematia, which yet are evidently elements produced, and of brief duration. From the point of view of ultimate physical constitution, of the mode of molecular collocation, we must consider every living element as being formed by a blending, molecule by molecule, of immediate principles, belonging to the three classes already indicated. All these immediate principles are dissolved in one of them, in water, which in weight is by far the most important body. In effect, living elements need a certain minimum of con- stituent water without which they can neither get nutriment nor as a result perform their functions. In the vegetal elements, as Sachs remarks,! we can prove this intimate blending of the immediate principles, by extracting from those elements, by the aid of certain solvents, substances chemically determined, without thereby changing the form of the histological skeleton. There exists between the anatomical vegetal elements and the animal elements an important difference in the degree of chemi- cal stability. The animal elements are much more easily alter- able by physical and chemical agents. In plants there is a certain degree of mineral fixity manifestly in relation with their smaller degree of vital perfection and activity. MM. Naegeli and Schwendener, studying carefully the play of. pola- vised light in the vegetal cellular membranes, the particles of starch, and also in the vegetal crystalloidal bodies, have found that in these vegetal tissues and elements there must be crystal- lised molecules birefringent and with double optical axes. These facts are perfectly in accordance with the difference of chemical composition of tissues in the two organised kingdoms. We shall see in effect that the most characteristic chemical element of organised substances, azote, enters in relatively feeble propor- tion into the composition of plants. Now the presence of azote 1 J, Sachs, Traité de Botunique, p. 768. Paris, 1874. 49 BIOLOGY. [Boox 1. coincides always in living beings, with a more elevated degree of vitality, a greater molecular mobility. The action of certain chemical and physical agents on the anatomical elements is in manifest relation with their constitu- tion, In effect brought into contact with solutions of bichlorure of mercury, of perchlorure of iron, of chromate of potash, of alcohol, and of other substances eager in their thirst for water, the anatomical elements lose their form and condense ; for they then lose their constitutive water! It is for this reason that alcohol definitively arrests the movements of the most resistant of the animal elements, of the vibratile cells, of which we have presently to speak, and that it kills in like manner the vibrions and the spermatozoaries. Heat, on the contrary, first of all accelerates the vital pheno- mena; under its influence the mobile cells move with more rapidity, the functions of plants ard accomplished with a greater energy ; for a certain elevation of temperature facilitates the chemical reactions and renders the osmosis more rapid. In like fashion diffusion increases with temperature. For chlorohydric acid we have in effect the following gradation :— Diffusion at . . . . . 15° 5*= 1 is ie ee we a Oe BAD 9 yw we we BB" = 17739 ma js 3 & ww =e 49° = Dele But if the temperature continues to rise, the functional exci- tation promptly reaches a maximum point, beyond which it first of all decreases and soon is annihilated. Because the heat diminishes by evaporation the constitutive water of the elements, and alters the composition of the albuminoidal substances when it does not coagulate them ; a result which is irremediable. Sub- jected to atemperature too elevated, the anatomical element soon dies ; while cold, which likewise slackens and stops the nutritive phenomena, does not always destroy them, sometimes merely 1 Ch. Robin, Eléments Anatomiques, p. 20. Cuar. v.] CONSTITUTION OF ORGANISED BODIES, 43 suspends them. The reason is that the vital activities and pro- perties are directly and solely derived from the physico-chemical properties in the midst of the anatomical elements. Consequently we see them grow stronger, or languish, vanish, reappear, or hasten to final extinction, from the sway of the molecular move- ments and mutations of which they are the expression. 2. Histology of Plants. The vital functions are less numerous, less specialised in the plant than in the animal, it being understood of course that we except the most inferior organisms in the two kingdoms. Weare therefore justified in supposing, a privrt, a less sharp specialisa- tion in the form of the elements. This is what is actually the case. While in the superior animal we find varied histological types very clearly distinguished from each other; in the plant, on the contrary, the elementary forms are less decided, less dis- similar, and sometimes they can be supplemented physiologically. It is from the microscopical anatomy of plants that has sprung the cellular theory, so contested at present in France, but gene- rally admitted in Germany, and according to which every ana- tomical element, vegetal or animal, has as direct origin a simple cell. In effect, in the vegetal world, the utricular, the cellular type greatly predominates. Every plant, from the simplest to the most complex, is formed by an aggregation of cells, or of fibres manifestly originating in cells. Every complete anatomical vegetal element is a cell formed of a double wall, of a content, and of one or more nuclei. The external cellular envelopment is constituted, chemically, by a ternary substance united to certain salts; this is the cellu- lose, composed of carbon, of hydrogen, and of oxygen. The chemical formula of the cellulose is analogous to that of sugars. Tt is C'2 H!°Q!, When the histological element is complete, this external membrane is interiorly lined with another very thin vesicle; but the second contains azote : it is albuminoidal. This azotised membrane englobes a semi-liquid substance and one or 44 BIOLOGY. [Boox 1. two small spherical or ovoidal bodies, likewise azotised. These are the nuclei, in which are often included one or two nucleoles. These azotised portions of the cell appear to be the seat of a nutritive movement more intense than the others. They appear also to be bound up with the period of development; for when the cell has lost its fluid content or protoplasm, it becomes incapable of growth and of multiplication. The contents of the vegetal cells are normally liquid or solid. Liquid they can be formed of oil or of water, holding in sus- pension either molecular azotised granulations; or particles of fecula, or drops of oil or of resin, or finally, small green bodies, very interesting, called chlorophyllian bodies, It is to these last corpuscles that the green parts of plants owe their colour. The liquid contents, non-oleose, are generally called protoplasm by the botanists. According to certain botanists, this proto- plasm is the really important part of the cell; it secretes the enveloping membranes, and the nuclei come forth from it by differentiation. In any case, this protoplasm is assuredly albuminoidal, for it precipitates through the chemical agents which precipitate albumine, and iodine communicates to it the yellow coloration which it gives to azotised organic substances. The internal vesicle, the protoplasm, and the nuclei form an albuminoidal whole, which Dutrochet was the first to succeed in isolating, by destroying the external membrane with nitric acid or dilute caustic alkalis. To constitute the diverse vegetal tissues, the cells assume various forms. For instance, the vegetal vessels by which, espe- cially in plants, the liquids and the gases circulate, are at the outset formed of cells juxtaposed longitudinally, After taking this linear arrangement the cells are cemented, and their walls are reabsorbed at the points where there is contact. The com- munication once established, the contents of the cells in their turn disappear, and the canal is formed. If the vascular bundle is perfect, every trace of cellular cementation completely dis- Caap. v.] CONSTITUTION OF ORGANISED BODIES. 45 appears; but in the case where the fusion of the elements has been less complete, the vessel remains nodose, being fashioned in the likeness of a chapelet.1 It is then called utriculous. Some- times, instead of being juxtaposed in linear series, the formative cells assume the shape of a vascular network. According to M. Ch. Robin,? we are able in vegetal tissues to distinguish as clearly as in animal tissues a small number of histological types. These types have as origin a cell ; but from their advent they bear a distinct physiognomy, and they are never seen undergoing or accomplishing mutual transformation. The first of these types is that of cells properly so called, offering moreover a certain number of varieties according as they are spheroidal, ovoidal, fibroidal, stellated, or cylindroidal. It would be needful to range in this class the cells of the epidermis of plants, those of the cork-tree, of cambium, and of marrow. We might naturally add the monocellular plants, such as the red utricles which sometimes give a red tinge to the snow of the Alps (protococeus nivalis of Saussure), and the diatomous plants. The second type is that of the filamentous cells, all more or less cylindrical, and eight or ten times longer than they are broad. We may cite as an example of filamentous tissues the cells forming the mycelium of the cryptogams, and also certain monocellular infusoria, such as the bacteria and the vibrions, if indeed we admit that botany can claim as belonging to its domain these dubiously-defined organisms. Every plant solely composed of the two histological types spoken of above, is a cellular plant. “The fibrous cells represent the third type. These are they which, juxtaposed lineally, form the ligneous fibres of wood and of liber. Finally, the vascular cells form the fourth type. These are they which by their linear juxtaposition and the partiel reab- sorption of their walls, constitute canalicules—vessels. To the ' In the sense of rosary or string of beads.—Translator. 2 Bléments Anatomiques. [Boox 1, BIOLOGY. 46 type of vascular cells belong the trachean cells with spiral filament, the punctuated cells, and the laticiferous cells. ST[90 peyenqound ‘q— TOPle Oy Jo yy 4 S ouBIQuieU aepNqy rT. QO OF GRECO OTT Ie CQOOVOOS 556 OO IMallelo role} O98 CXOLEYS) ale] © SOG [S¥o) Lele © @f S silt! [is] soo seo Thee (aa ‘D OCC COLT, dD “peeryy PuNoM oxXT 1190 Aey}OUR ‘9Q— s}imgy JO vurdyous.ced) sousst} [e}0F0A. OS00T “TRA eNI]Te0 oY} Wosy poyeredes pus “Tong ‘A1rerds punom peorqy ext T1399 ‘&—s1ezrU0d oYy Jo “ear} YOIB] OT} JO T]99-01qy Snoeust, ‘q—euid oud JO T1e)-01qy SNOETSIT 10 pozesuoye ‘QO—(uo os pue *a0r4 9q} JO ST[90 [eoltoyds ‘gq —-spoofonu YyIM snejont ‘9 + wse(doyoid ‘¢ peqyorouod sey wse[doqoad oqy, f TOYOoTE TITY poqzery T17? Teaadeq, Cuar. v.] CONSTITUTION OF ORGANISED BODIES. 47 We are disinclined to admit that this classification, so sharp, so decided, can be admitted in all its inflexible rigour ; but we may accept it as giving a good general view, as grouping under a small number of heads a great variety of vegetal and histological elements, 3. Histology of Animals. The anatomical animal elements differ in general from the vegetal elements in the threefold point of view of chemical composition, of structure, and of form. In effect, while in plants the anatomical element is in chief part constituted by a non-azotised ternary substance, the cellulose; the animal elements, on the contrary, are formed especially by the quaternary albuminoidal substances. No doubt we en- counter in animals ternary substances analogous to the starch and the cellulose of plants, but partially, secondarily, and in small quantity. Jtis thus that we find in the tegument of the arthropods, and even in all classes of the invertebrates, a matter very analogous to the vegetal cellulose, chitine, which can -trans- form itself into glueose. But these points of detail do not weaken the value of the grand general fact enounced above. The general differences of structure are perhaps in proportion to the differences of chemical composition. The albuminoidal substances,are in effect essentially colloidal, and consequently must tend to a more unfixed morphology. Thus, while in the vegetal cell we generally find an enveloping membrane with the exactest limits, this membrane is often lacking in the anato- mical animal elements. In the latter case the element is a small figurate glomerule, approaching more or less the type fibre or the type cell, and usually furnished with one or more nuclei and nucleoles. From the point of view of form, the difference between the histological animal elements and the histological vegetal elements ‘is more marked still. The vegetal histological types are few, and are all related directly and visibly to the cell. But the 48 BIOLOGY. [Boox 1 anatomical animal elements have forms much more varied. In those of them which merit the name of jibres, there is often no longer any trace of the cellular form ; and the animal fibres are not even derived from original cellular elements, if we admit with M. Ch. Robin the spontaneous genesis of the anatomical elements in the blastemas. This theory of the spontaneous apparition of the anatomical elements in the living liquids has hitherto been rejected in Germany, where is adopted in all its rigour the axiom of M. Virchow—Omuis cellula e cellula. In accordance with the terms of the German cellular theory, every anatomical element, whatever it may be, has as origin a cell; it comes forth from it by gemmation or segmentation ; and every element which departs from the cellular form is simply a metamorphosed cell. It is not easy to understand how asser- tions so directly opposed should be passionately maintained on both sides by observers equally skilful, We are compelled to admit that on each side there is a portion of truth. We shall see when treating of generation that the French school wishes to reject reproduction by division and gemmation in the vegetal kingdom, in the initial period of embryonic animal life, and in certain produced elements. According 4o this school, most of the elements called constituent, that is to say, forming really the framework of the animal organism, spontaneously arise, by synthesis, by genesis in the living liquids, alike in the embryoh and the adult. Let this be as it may, the cellular theory is convenient for classifying the anatomical elements. In effect, while the parti- sans of spontaneous genesis admit no bond of direct kinship among most of the anatomical elements, strive especially to note dissemblances and to multiply species, the partisans of the cellular theory, preoccupied with the idea of a common origin, dwell especially on resemblances, and thus arrive at forming a very small number of elementary histological groups. According to them there are only four types of anatomical elements and of CHar.v.] CONSTITUTION OF ORGANISED BODIES. 49 animal tissues, namely: 1. The elements of the cellular or con- nective tissue; 2. The cells remaining autonomous, that is to say, the epitheliums and the glandular cells, to which might be added the globules of the blood; 3. The elements of the mus- sular tissue; 4. The elements of the nervous tissue. The first of these tissues forms the general gangue, the support of all the other tissues and elements. It is essentially composed of cells called stedlated cells, having a diameter of from 0™™, 050 to O*™, 060. These cells enclose a nucleus containing a nucleole. They emit fibrillary prolongations concurring to form the fibres of the cellular tissue, and which often seem to be anastomotically connected with each other. Other fibres called laminous fibres, because they are slightly flattened, form them- selves in that same cellular tissue round elongated nuclei, called embryoplastic nuclei. The whole resembles a long wire- drawn spindle, The laminous fibres emanating from those cells form the chief part of the cellular tissue. They are very long, grouped in bundles, and with an average breadth of 0™™, 001. According to this theory, we regard as appertaining to cellular tissue the cartilaginous cells and the osseous cells. All these cells are nucleated. The first are round or ovoid, the second are irregular, and emit in every direction filiform prolongations, anastomotically intertwined. These last cells, which form ‘the living mechanism of the osseous skeleton, have been called stellated osseous corpuscles. The cells called autonomous comprehend the globules of the blood, which we shall describe further on, and the epitheliums. Of these last elements, some serve to line, while protecting, the animal membranes, the skin and the mucous membranes, while the others play in the secretions an extremely important part, to which we shall have occasion to return. The epitheliums have as their first division the pavimentous epitheliums, .large cells flattened, and usually polyhedrical, because they are subject to reciprocal compression. ; fey contain a nucleus and a nucleole, and their whole aspect vividly Rr 50 BIOLOGY. [Boox 1. recalls a pavement of hexagonal bricks. In animals they clothe the mucous membrane with many conduits, and play especially the part of a protecting varnish. As related to them may be regarded the epidermic cells. Other epithelial cells are cylindrical or cylindro-conical, Sometimes the free surface of these cells is furnished with fine and mobile cilia, In that case the epithe lium is called wibratile epithelium. We have besides to mention [the Biehl the spherical epithelium. We find it especially in the glands where its function is to form, at the expense of the plasmas and the blastemas, the special bodies destined to be secreted. Finally, we signalise here for the sake of remembrance the muscular elements, distinguished into fibre-cells and into fibres properly so called ; then the elements of the nervose tissue, fibres, and cells. We shall have elsewhere to describe in detail the form, the structure, the functions of these elements, which may be characterised as aristocratic, CHAPTER VI. OF LIVING LIQUIDS. For centuries the humofrists and the solidists have filled the world, we mean the small physiological and medical world, with their discords, with their furious strifes. As in all long wars, there has been in this many a peripetia. Sometimes the triumph- ant humours submerged their adversaries ; sometimes these, offer- ing resolute front with their serried ranks, seemed to have fixed victory for ever to their banners. Observation and experience have ended by imposing on the belligerents their sovereign arbitrament. It is at present demonstrated that between the solids and the liquids of every organism there is less difference than had long been believed. The solids come forth from the liquids ; they come forth from them incessantly and return unto them. Finally, between the solids or anatomical elements and the living liquids, that is to say, the blastemas [blastemata] and the plasmas [plasmata], there is a great analogy of composition. The name of bdastema is given to every living liquid, that is to say, endowed with nutritive mollecular movement and interposed between anatomicalelements. The plasmas are alxo living liquids, but circulating in canals, the blood and the lymph of animals thus circulating. Blastemas and plasmas have a great analogy with each other if we look at them in a general manner. They -both are living ; they both equally contain materials of assimi- lation destined for the anatomical elements, and materials of disassimilation which come forth therefrom, crystalloidal sub- stances in process of transforming themselves to become assimi- lable or organisable albuminoidal substances, and albuminoidal EB 2 52 BIOLOGY, [Boox 1. substances tending to become crystalloidal and to be expelled from the organism. The vitality of the blastemas is naturally, greater than that of the plasmas ; they may almost be considered as elements which have lost their forms; physically, they are viscous liquids in which, generally, granulations are interspersed. They are the organisable liquids by excellence. It is in the midst of the blastematie liquids that the anatomical elements of the embryons, or of the tissues constituted in process of development or regeneration, have their origin, for instance, after a wound. 1.—Vegetal Blastemas. The plants, even the most perfect, the dicotyledons, have no special circulatory system. In the dicotyledonous tree, the terres- trial sap mounts through the tissues of the wood, filling the intercellulary spaces, the canals, and passing by endosmosis from cell to cell, from fibre to fibre. Arriving at the leaves it undergoes an important modification, with which we shall have to occupy ourselves; then it redescends by the more superficial tissues, and especially by the young intermediary tissues between the bark and the wood. The descending sap, that which has been elaborated in the leaves, must be considered as a living liquid, as a blastema; also, as it goes along we see it organising itself either in a direct manner or through the agency of pre- existent anatomical elements. In truth it is a liquid holding a middle position between the plasmas and the blastemas. The blastematic liquid} whence spring the buds, is thoroughly comparable with the animal blastemas. Like these last it is in part exuded by the anatomical elements, that is to say by the vegetal cells which it drains off and dissevers. This mode of formation recalls that of the vegetal and animal embryonary blastemas. The true vegetal blastemas resemble much the semi-liquid azotised content of the vegetal cells, namely, that intracellular substance endowed with spontaneous movements, having its Cuar. vi] OF LIVING LIQUIDS. 53 special molecular affinities, refusing, for instance, as long as‘it is living, to let itself _be imbibed_by colouring matters. Now we know that this intracellular protoplasma offers all the chemical reactions of the true albuminoidal matters (albumine, fibrine, caseine). Iodine gives it a yellow colour ; alcohol, the mineral acids, and heat coagulates it. ~ Chemically, the vegetal blastemas are constituted by water, : by albuminoidal substances, and by some salts. ( 2.—Animal Blastemas, There has been a wish to limit the name of blastemas, in the animal economy, to the interstitial liquids alone in which new anatomical elements are formed, that is to say, to the intercellu- lar liquids of the animal embryons, before the formation of the vessels, to the organisable liquids which are produced in a wound in process of cicatrisation, finally to the liquids of the serous cavities. But in biology, as in all other natural sciences, if it is useful to divide, to classify, it is wise not to accord to divisions , and classifications an absolute value. The frontiers which we are obliged here and there to mark out in the vast field of the living world to aid the feebleness of our memory have only a relative value. In effect, in the organic world, even taken generally, all is gradual modification, gradual transition. If this is true, as incontestably it is, in the classifications of natural history, properly so-called, how much more must it be so when the aim is to ascertain the constituent parts of one and the same organism 4 If we reserve the name of blastemas to the small number of liquids living, interstitial, organisable, and generative, what are we to do with the other interstitial liquids, with those which bathe the elements of the tissue called conjunctive [connective], of that tissue comparatively coarse in its morphology which serves as gangue and as support to all the others? And in most tissues, wherever the elements do not touch each other at every point of their surface, is there not an interstitial liquid, coming 54 BIOLOGY. [Book 1, on the one hand from the tissues, and on the other from the exterior medium? But these tissues constantly grow larger from birth to the adult state or age, that is to say, that incessantly during this lapse of time new elements arise and gain place in the midst of the old. Evidently these elements are formed at pas expense of the interstitial liquid, which consequently then becomes a true formative blastema. Let a freshwater polypus be sectionised into several frag- ments: immediately each of these fragments strives to complete itself, strives to remake a complete individual; but this new in- dividual once formed is not more voluminous than the fragment whence it took its birth. It has therefore modelled and consti- tuted itself at the expense of the interstitial liquid, bathing the cellular tissue of the hydra; therefore this liquid is formative ; therefore it is a blastema. But blastema is likewise the inter- -cellulary liquid of the grey cerebral substance, that of the umbili- eal cord, that of the marrow of the bones, and so.on. ‘The chemical composition of the animal blastemas is a little better known than that of the vegetal blastemas. Like these last, they are composed of albuminoidal substances, of salts, and of regressive crystalloidal substances ; lastly, of a great quantity of water. But besides these general characteristics it has been successfully demonstrated that the blastemas of the superior ‘animals have a composition different from that of the blood and the lymph, from which chiefly they are derived. They possess fibrine and albumine in smaller quantity. Largely albumine takes in them its chemical, soluble, and assimilable form ; it be- comes albuminose, no longer coagulates from heat, and coagulates imperfectly and with difficulty through the acids. Fibrine is no longer found therein, and nothing is more natural, for we know that to become assimilable, nutritive, fibrine needs to be trans- formed isomerically into albuminose. There has been a desire to make of the chemical instability of the blastemas a distinctive characteristic. No doubt the blaste- mas are ina state of perpetual mutation; they are never iden- Cuap. vi] OF LIVING LIQUIDS. 55 tical for two moments of duration. But we can say quite as much of the blood, of the lymph, of the histological elements them- selves, forasmuch as the movement of continuous renovation is the primordial condition of life. On the whole, between the anatomical elements, the blastemas, and the plasmas, there is from the chemical point of view, merely the difference in the proportion and the nature of constituent immediate principles, but a difference graduated from each to each. They are three forms of living matter, analogous to each other and engendering each other. 3.—Of the Plasmas. In the plant, the imperfect division of physiological labour, and the confusion of functions, are so great that we find it difficult to classify the organic liquids. We have signalised the liquids evidently blastematic of the vegetal embryon, of the buds, the liquid semi-blastematic and semi-plasmatic which is called sap. Further on we shall say some words in reference to the secretion of the vegetal glands and of their secreted products; and thus we shall have passed in review all the vegetal organic liquids. The thing is less simple in animals, or at least in the superior animals. The division of labour is more advanced in the tissues and the liquids, and we must carefully classify both of them. In the superior animal the organic liquids can first of all be divided into two great groups corresponding to the two great divi- sions of the solid elements; they are the group of the constituent humours, and that of the produced humours. The chemical composition of each group, and even of the humours of each group, is very various ; but in a general manner we can say, that they all contain immediate principles of the three orders :! 1. Principles of mineral origin (water and dissolved salts) ; 2. Principles of organic origin, some crystallisable, others coagulable (urea, creatine, lactates, choleates, and so on) ; 1 Ch. Robin, Des humeurs, p. 20, 21, 8vo, 56 BIOLOGY. [Boox 1, 3. Principles non-crystallisable, but coagulable, met with in all the humours, except the bile, the urine, and the sudor. These last immediate principles are the albuminoidal substances properly so called, and the saccharine substances, both of them having the property of dissolving certain mineral or mineralised compounds little or not at all soluble in water. It is thus that albumine fixes silica, phosphate of lime, urates, and so on. The humours produced or humours of secretion, are formed in the economy at the expense of the constituent humours, and generally by special organs called glands. By and by we shall have occa- sion to study their process of formation. They comprehend the extremely aqueous liquids, produced on the surface of the mem- branes, called serous, which cover certain viscera (brain, heart, lungs, intestines, and so on); the liquids bathing the articular surfaces or synovial liquids ; lastly the sperm, the milk, the muci, the salive, the bile, the intestinal juice, and so on. In connection with the produced humours we may view the liquids simply excreted, that is to say, separated from the con- stituent humours wit without chemical modifications (sudor, urine, amniotic liquid, allantoidian liquid, pulmonary exhalation). All these liquids, save three, are alkaline. The three liquids habitually acid are the gastric juice, the sudor, and the urine. However, this last liquid is sometimes alkaline, sometimes acid, sometimes neutral, in man, at the different stages of digestion. In the herbivorous mammifers it is normally alkaline. But here also the alkalinity depends on the digestion, In effect the urine of the herbivora becomes acid if we feed them on animal ali- ments, or, which comes to the same thing, if dieting them, subject- ing them to inanition, we force them to live at the expense of their own substance. The alkalinity of the animal humours is usually due to salts of bibasic or tribasic soda; but free soda we never meet with in them. In connection with secretion and excretion we shall speak in detail. of the produced humours, contenting ourselves here with indicating their principal distinctive characteristics, Cnap. vi.] OF LIVING LIQUIDS. 57 ‘We have now to describe the humours of the first order, the humours constituent, living, those which may be regarded in some sort as liquefied anatomical elements. These liquids, which | exist with supreme distinctness only in animals with complex structure, furnished with circulating apparatus well defined, are only two in number, the blood and the lymph; for we must con- sider the chyle, that is to say, that ultimate product of digestion circulating in the lymphatic vessels, a dependency of the lymph. The blood and the lymph are contained in circulatory systems, ramified and inclosed in every direction. These circulatory systems imprison the liquids which are formed in them, without, normally, permitting them to break forth in mass. But across their walls they leave an easy passage to many materials coming either from the tissues, or from the ambient medium and to many others which escape from the blood and the lymph, either to nourish the tissues, or to be expelled as unworthy from the frontiers of the organism. This double movement of coming and going, of exchange of materials, is effected simultaneously, like the nutritive assimila- tion and disassimilation in the solid elements. In truth the blood and the lymph are living liquids, in process of perpetual renovation. Incessantly they are formed in the system of the canals where they circulate without being destroyed. The vascular walls which contain the constituent liquids do not seem notably to modify the chemical composition of the sub- stances which traverse them. The part they play is especially physical, osmotic. Therefrom it results that the blood and the lymph borrow their constituent materials already formed from an ambient medium, either from the grand cosmic medium, the air for example, or from the organic medium, the tissues, the myriads of anatomical elements which compose the body of the superior animals. Considered as organised liquids, the constituent humours neces- sarily contain immediate principles of the three classes ; but those of the third class, the albuminoids of organic origin, not crystal- lisable or coagulable, predominate therein. They are albumine 58 BIOLOGY. [Boox 1. or rather serine,! and plasmine, which severed from the living organism, evolves itself into fibrine spontaneously coagulable and into fibrine called liguid. To these albuminoidal substances we must add variable proportions of peptones and albuminose, that is to say, of albuminoidal alimentary substances liquefied and absorbable. The blood and the lymph are not homogeneous, physically simple liquids. We meet with, in them, floating bodies which are true free anatomical elements. These bodies have been called globules. The liquids in which these globules swim in immense numbers have received the special name of plasmas. These plasmas isolatedly considered are endowed with nutrition : they are consequently living. They contain in proportions almost equal, immediate principles of the three orders; nevertheless the coagulable principles predominate. If nutrition ceases ina plasma, that is to say, if this liquid dies, its composition immedi- ately changes; the albuminoidal principles which it contains evolve into a liquid portion and another portion spontaneously coagulable. It is this which, in animals provided with a circula- tory system, produces the cadaveric rigidity. The office of the plasmas is of supreme importance; but to obtain a complete notion thereof we must figure to ourselves. what every complete organism is from the point of view of tex- ture. At the lowest degree of life and organisation, we find monocellular beings, free anatomical elements, simple infusoria,. living habitually in the water; for directly or indirectly, the anatomical elements are generally aquatic entities. ‘These the monocellular organism absorbs and assimilates, disassimilates, and secretes, directly borrowing materials from the ambient me- dium, or restoring them to it. In beings a little more complex composed merely of cells identical with each other, and simply juxtaposed, the nutritive process is scarcely more complicated. In effect, the polycellular organism, with cells which resemble each other, is definitively nothing more than a collection of juxta- 7 * Ch. Robin, Des Tissus, p. 21. Cuap. v1.J OF LIVING LIQUIDS. 59 posed monocellular organisms. However there is usually a gene- ral enveloping membrane and afterwards an interstitial liquid, a sort of blastema, playing, in respect to the anatomical elements of the polycellular organism, the part of an artificial medium. The cells now no longer plunge direct into the cosmic medium ; they are protected and isolated by an organic, an elaborated liquid. In the extremely complex organisms, for instance, in the superior animals, the intrication of the texture is much greater, Here the anatomical elements are not formed in one mould only ; they are differentiated according to multiple types, and each type assumes a diverse function. One, for instance the epithelial type, supplies to the living membranes a protecting varnish ; to the glands a special agent of secretion; another, for example, the tissue called cellular, serves as gangue, as bond, as support to all the tissues, apparatus and organs, while opening besides a passage to blastematic liquids. A third, exemplified in the osseous element, furnishes to the organism a solid framework. Lastly, the muscular fibre and cell impress on the pieces of the living apparatus the necessary movements, while the nervose fibre and cell endow the organism with sensibility, with will, with thought, and are the sentient soul of the entire being, of which they assume the conscious direction, and so on. But in order that these anatomical elements so diverse, so numerous, grouped into tissues, into organs, into apparatus, into special systems, may live, may perform their functions, may co-operate, itis needful for them to be almost completely withdrawn from the rough and capricious influences of the exterior world; they must perform their functions in an artificial medium, alive like themselves, in which they find a temperature little variable, a magazine always well provisioned with substances elaborated and assimilable, suited to repair their losses ; lastly, a place of discharge, into which they throw their used materials, that have become unfit to figure in the vital movement. These nutritive media, artificial, liquid, consequently appropriate for the aquatic life of the anatomical] elements, are the plasmas, always in movement, always renewed, 60 BIOLOGY. [Boo 1. yielding incessantly materials to the exterior world and to the tissues, and incessantly taking them back, having a temperature nearly equal, as long as that of the exterior medium does not suffer very great oscillations. For the anatomical elements, the plasmas are a veritable living atmosphere. 4.—Of the Blood. In the vertebrates the most important of the plasmas, the blood, is a red sap unceasingly circulating with greater or lesser activity. In the invertebrates the blood is animated by a much slower movement of translation. It is contained in apparatus not so well constructed, and is generally colourless and trans- parent like lymph. Often even the blood and the lymph of the invertebrates are confounded; where there are distinct san- guineous cavities and lymphatic cavities, as happens in some annelate worms, the blood is tinted with a special colour—it is sometimes red, sometimes yellow, green, violet, or bluish. The sanguineous cells which it sometimes in that case conveys, are almost always colourless. However, there are sanguineous, coloured globules in the terebella and the cephalopods. The blood of the vertebrates, with which we have especially to occupy ourselves, is, according to a felicitous comparison of Cl. Bernard,? an interior medium in which live the anatomical elements as the fishes live in the water. These anatomical elements, moreover, retain in the blood their physiological inde- pendence, and though drawing their nutritive materials from the sanguineous plasma, they donot allow themselves to be imbibed by it, which is an essential condition of endosmotic exchanges. Consequently we see, for example in the blood of the vertebrates, potash dominating in the globules, and soda in the plasma. The physical qualities of the blood of. the superior vertebrates 1 R. Wagner, quoted by Fr. Leydig (Traité d’Histologie de ? Homme et dis Animaux, p. 509, Paris, 1866.) * Cl. Bernard, Legons sur les Propriétés des Tissus vivants, pp. 55-58. Paris, 1866, Svo. Cuap. vi] OF LIVING LIQUIDS. 61 are well known. In these perfected organisms the blood is a liquid slightly viscous, of a purple red in the arteries ; that is to say, when it is freshly impregnated with aérian oxygen, but of a blackish tint, more or less deep in the veins; that is to say, when from contact with the tissues it has exchanged its oxygen for carbonic acid. It is well known that the temperature of these two bloods differs, that of the venous blood being a little more elevated in the right ventricle of the heart and in’ the deeper veins—an elevation which we must evidently attribute to the chemical reactions of nutrition, the residua of which the venous blood collects. It is also known that the blood, as soon as it is drawn from the vessels, separates into two parts—a red coagulum containing the globules,-and a liquid part of a lemon yellow, which is called serum. ‘ The blood, we have said, is a medium from which all the anatomical elements of the organism derive the materials needful to their life, and into which they pour all their nutritive residua ; its chemical composition must therefore be very complex. We find therein in effect immediate principles of the three classes, and we find therein in great number. We must content ourselves, therefore, with signalising the chief of them. The principles of the first class, wholly mineral, are first of all water, which quantitatively is the most important element, as, moreover, the figure for the density of the blood shows, which on an average is only 1,050. In quantity, water in man repre- sents from 905 to 910 thousandths of the blood. The proportion, however, notably varies ; it is more considerable in the infant, the young man, the pregnant woman ; in short, wherever the formation of new anatomical elements necessitates the fixation of many solid materials. In this liquid mass all the other immediate principles are dissolved, and the globules travel along. The immediate gaseous principles of the first class are oxygen, azote, and hydrogen. The first of these gases, which is by far the most important, comes from the exterior air from which it is 62 BIOLOGY. [Book 1. borrowed by the respiratory organs, as we shall see when speak- ing of respiration. It is oxygen which, combining with the globules or hematia, gives them the vermilion tint which they have in the arterial blood. But the globules do not keep their oxygen long. Elaborated in the fine circulatory vessels, where they are in almost immediate contact with the anatomical ele- ments, they surrender to them their vivifying oxygen, indispensable to the chemical reactions of nutrition. In exchange they take back the gaseous residuum of the oxydation of the tissues, the carbonic acid, which gives them a blackish tinge, that of the venous blood. Tt must be observed that the sanguineous globules never completely despoil themselves of one of these gases to impregnate themselves completely with the other. They retain them simultaneously, oxygen predominating in the arterial blood, carbonic acid in the venous blood. It suffices, besides, for the gases to be in equal quantity in the blood for the globules to become blackish. The change in the proportion of the two gases is not effected suddenly, but by degrees—in proportion as the arterial blood goes away from the lungs and the heart to approach the tissues, the oxygen gradually yields the place to the car- bonic acid. The water of the blood is not normally free; it is found com- bined with albuminoidal matters. This is why it cannot filtrate mechanically through the vascular walls. Almost in totality it comes from the aliments, for it is doubtful whether any notable quantity thereof is formed in the organism. The immediate saline principles of the first class which are contained in the blood are the chlorures, the chlorohydrates, the sulphates, the carbonates, the phosphates, and so on. Of all the salts, the chlorure of sodium is by. far the most abundant in the blood of man. The proportion of the salts varies, besides, according to the animal species. The phosphates predominate in the blood of the carnivora, but yield the superiority to the carbonates of soda and of potash in the herbivora. This is, after all, as.we have remarked in refer- Cuap. v1] OF LIVING LIQUIDS. 63 ence to urine, a pure affair of alimentation. It is to the basic phosphate of soda and to the carbonate of soda that the blood owes its alkaline reaction. M. Ch. Robin! remarks that the different salts of the blood serve as mutual solvents, and that the phosphates and carbonates of soda permit the sanguineous liquid to dissolve a great quantity of carbonic acid. In the economy, in effect, the blood is never saturated with carbonic acid. Venous blood brought into contact ° with carbonic acid, still suffices to dissolve thereof 0™* 48 in 100. Thus it always seeks this gas eagerly, and is ready to disengage therefrom the anatomical elements. We must cite, by way of remembrance, traces of silica, of manganese of lead, of copper, fortuitous mineral elements, little or not at all useful to nutrition, but drawn along with the others into the living organisms. It is otherwise with iron, which seems to play an important part, to form a really constituent portion of the sanguineous globules, though it exists in a very small quantity, for the total quantity of iron in the blood of an adult man is reckoned to be not more than one gramme.” Other salts, the salts of soda, of potash, of lime, belong like the preceding to the immediate principles of the second class. They are organic salts, nutritive wastes. Let us mention the urates and inosates of soda, of potash, and so on, which probably result from the disassimilation of the muscular tissue, &c. But the disassimilation gf the anatomical elements gives birth to many other principles more complex, more organical, to sorts of alkaloids. These crystallisable principles, always in a state of liberty in the blood, are urea, creatinine, creatine, inosite. There has been an attempt to determine the place of origin of these diverse products. It is said that creatine and creatinine come from the muscles, urea from the tissues, fibrous, laminous, serous.? 1 Ch. Robin, Des Humeurs. 2 4 French gramme is nearly equivalent to nineteen grains English.— Translator. 3G, Sée, Du Sang et des anémies, 64 . BIOLOGY. {Boox. 1. We may view in connection with these substances cholesterine and seroline, formed probably in the nervous tissue. All these bodies pass by osmosis through the fine capillary vessels, and sojourn in the blood till they are secreted or excreted therefrom. The other azotised substances of the blood belong to the third class of immediate principles. They are the albuminoidal sub- * stances, properly so called. Urea, creatine, creatinine, and so on, are azotised regressive principles, residua of disassimilation : they form part of the material current coming forth from the organism. On the contrary, the other albuminoidal substances are the residuum of the alimentary elaboration. They are des- tined to repair the waste of the tissues, and form part of the material current entering the economy. When the blood of a mammifer is drawn from the vessels, and allowed to rest, it separates into a red clot and a yellowish liquid. The clot is composed of an azotised complex substance, which has been called fibrine, because it has then a fibrillary aspect, and this coagulated substance retains in its meshes the red globules. The ambient liquid contains in solution another azotised sub- stance, denominated albumine, because it has affinity with the albumen of the egg, though containing a half less sulphur. For a long time there was an erroneous belief that fibrine and albu- mine have as distinct existence in the economy as in the blood when drawn. Fibrine and albuming are, however, isdmeric, albumine merely containing a little more water. From important analyses of the blood made by Denis, of Commercy,? it results that in effect the blood contains albumine, which Denis prefers to call serine ; but instead of fibrine there is in the blood another analogous azotised substance, which he calls plasmine. This plasmine, he thinks, evolves itself in the blood when drawn, and thanks to the intervention of the globules, into a coagulable part called fibrine, and into another soluble albuminoidal substance, 1 Denis, Comptes rendus des Séw del Académie des Sciences. ‘Paris, 1856 and 1858.—Mémoire sur le Sang, Paris, 1859, 8vo. Cuap. vi.J OF LIVING LIQUIDS. 65 which remains in the serum with the albumine or serine and can be separated therefrom. That all these determinations of contemporaneous chemistry are destined to be maintained intact in the future we do not believe. In effect, the albuminoidal substances are extremely unstable ; those of the economy are probably isomeric, or nearly so. Their chemical formula has not even yet been determined. They are not naturally absorbable, except on condition of being soluble ; the fibrine and the albumine of the aliments are transformed by digestion into isomeric substances called peptones, albuminose, whose degree of relationship with the plasmine and the serine of Denis has not yet been determined. In short, these are questions the precise solution of which must be reserved for the chemistry of the future. To conclude what we have to say on the principal organic materials of the blood, let me mention the fine guttule of fat matter floating in the blood after digestion, in the state of emul- sion. These fat bodies are absorbed by the tissues, which yield them afterwards to the sanguineous liquid, in the state of com- bination, saline, saponaceous, and soluble (butyrates, phosphorised fat matters). Let me mention, lastly, a certain quantity of glucose or sugar of grape. , The mineral substances dissolved in the blood are not all in the state of simple blending. If we inject into the blood first of all 2 solution of a salt of iron, then a solution of prussiate of potash, we do not obtain the characteristic reaction of the salts of iron, the formation of Prussian blue, because the albuminoidal substances of the blood have at the very outset fixed the salt of iron, On the contrary, we obtain Prussian blue if we inject first of all the prussiate of potash, because the albuminoidal substances leave this salt free (Claude Bernard). 5.—Of the Red Sanguineous Globules, If we examine in the microscope a guttula of blood, we find small floating bodies, extremely numerous, pressed against each F 66 BIOLOGY. [Book 1. other, and every one of which seems to be an isolated cell. A more attentive examination soon shows that these bodies are rather glomerules than real cells, for they have neither nuclei nor enveloping membranes. They are small flattened disks, depressed in the centre on their two-faces, an arrangement which often simulates a nucleus. Their diameter is from 0™", 006 to 0™", 907, in the adult man. But their form varies in the series of the vertebrates, and also in man and the mammifers if we remount to the first stage of the embryological life. In effect, at the epoch when the embryon has only a length of 0™, 02 to 0™, 03, where the globules begin to appear, they are white, and have a veritable nucleus. According to some authors they then multiply by segmentation. They are now much longer, and their diameter attains 0™™, 010, to 0™™, O11. In the animal series we also observe very notable differences in the form, the volume, and the struc- ture of the sanguineous globules. As “4 long as we are simply considering the class of the mammifers, these differences are slight. However, the sanguinequs globules of the camel and of the llama have an ovalar ellipsoidal form, and re- semble those of birds and reptiles. In the elephant and in the didactylus sloth we also find sanguineous globules much longer than in the other mammifers. In the other classes of vertebrates the differences grow more striking. In all ee the vertebrates the globules are, as in Frog.—a and b front view and man, of a red colour by reflection, and Pte glebule, “500 diameters’ it is to them that the blood owes its Tee try aneuiecun ihe rutilant tint. In general the red glob- white Aatutee nutty veatlts ules of the mammifers are less volu- ofthe chyle, 800 diameters. rinoug than those of the other classes of vertebrates. They are elliptical and nucleated in the classes of Cuav. vi] OF LIVING LIQUIDS. 67 birds, of amphibia, and of fishes: elliptical only in the class of reptiles. There is no absolute rule, however. The fact of the existence of globules in the blood of an animal is very important ; but their form is much less so. We have seen that certain mammifers have elliptical sanguineous globules like those of birds. On the other hand, the humblest of the vertebrates, fishes of an inferior order, such as the genera myxine and petromy«on, having affinity with the celebrated Amphioxus lanceviatus, have like man sanguineous globules, circular and with double depres- sion. Lastly, as a second link of the chain between the branch- tostoma without globules,! as an invertebrate, and the fishes with globular’ blood, is found a fish with white, colourless globules, the leptocephalus. But, on the whole, in spite of some exceptions, the red globules, or hematia, are found in the blood of nearly all the vertebrates ; they are the anatomical and physiological sign of a complete organisation, of a more active respiration, of a higher vitality. In the blood of man and of the mammifers, the sanguineous globules are in immense number. According to Schumann, Andral, and Gavaret, the red globules in the humid state form in volume the half of the mass of the blood.? Furthermore, Vierordt has counted, in a cubic millimetre of blood, from 4,180,000 to 5,551,000 globules. The younger the individual the greater is the proportion of hematia. The blood of the adult man contains 302 thousandths according to Ch. Robin.? There is much more in younger persons, and in the new-born child the proportion rises to 600, to 680, and even to 700 thousandths. A German anthropologist, Dr. Welcker, has demonstrated that from the point of view of the form and the proportions of the cranium and of the face, woman holds an intermediate position between the adult man and the infant. In regard to the hematia, the relative propor- tion is the same, rising in women to 320 and to 400 thousandths 1 Retzius, J. Miller, De Quatrefages. ? G. Sée, Du Sang et des Anémies, p. 15. 3 Ch. Robin, Des Humeurs. F2 68 BIOLOGY. [Boox 1. The hematia are veritable histological elements floating in the sanguineous plasma. Like everything which lives, they assimilate and disassimilate incessantly, Each of them has probably only a brief duration. According to the German cellular doctrine, they spring in the embryon, from pre-existent cells, and multiply after- wards by segmentation, by cellular division : but the point is not one which direct observation has yet elucidated. It is certain, however, that the hematia are remade in the blood, for a few weeks or a month suffice to cure the anemia caused by too copious blood-letting or by excessive hemorrhage. In an animal sub- jected to abstinence, the globules diminish in number, lose their shape, and shrink. It is probable that incessantly the more aged of the hematia dissolve in the blood, and are replaced by hema- tia of new formations. These fresh growths have their birth either in the lymphatic glands, or in the special glands (thyroid body, spleen, and so on). The physiological characteristic of the hematia is the property they possess of absorbing liquids with a great energy. This property is inherent in their very substance, independently of their form. In effect, a solution of this substance grows red in contact with oxygen, and becomes less rutilant from contact with carbonic acid. The affinity of the substance of the globules for oxygen is quite comparable with that: of the green matter of leaves, chlorophyll, for the carbon of aérian carbonic acid. It is by reason of this powerful affinity for oxygen that in the sanguineous transfusion practised in men and the mammifers the injection of mere globules suffices to provoke real resurrections, The blood extracted from the vessels continues to appropriate oxygen and to exhale carbonic acid. From contact with oxygen the hematia swell, and tend to lose their double depression. Carbonic acid, on the contrary, makes them shrink. In like fashion in the vertebrated organisms, the function of the hematia is to imbibe many volumes of oxygen during their passage through the respiratory organs. Once impregnated with oxygen, the globules give to the blood a tint rutilant, vermilion. Cuap. vi.] OF LIVING LIQUIDS. 69 The blood is then called arterial: thereupon the globules are conveyed with their provision of oxygen into the circulatory apparatus. Soon they find their way to the finest vessels of this system, where they are almost in contact with the anatomical elements of the tissues. Between the globules and the anatom- ical elements an exchange of gas is-there accomplished which is one of the primordial acts of nutrition. In effect, the vital condition by excellence for every anatom- ical element is to be oxydized, more or less slowly. But this process of oxydation produces, along with other chemical com- pounds, carbonic acid gas, which, if it was not eliminated in the degree of its formation, would soon bring death to the anatomical element. The function of the red globules of the blood is pre- cisely to take back that carbonic acid, and to furnish in exchange their vivifying oxygen. The visible sign of this gaseous exchange is the change of coloration of the globule, which becomes blackish when it has parted with its oxygen to charge itself with carbonic acid. This black or venous blood contains much less oxygen than the arterial blood. According to Magnus, there is in the arterial blood 38 of oxygen to 100 of carbonic acid, and the proportion is only 22 to 100 in the venous blood. The venous blood is blood im- poverished by nutrition; it contains fewer globules, less fibrine, and on the contrary more salts, a certain number of which are nutritive residua.} Every anatomical element transforms oxygen into carbonic acid by the mere agency of nutrition; but it consumes a much greater quantity when it exercises a special function, and then the absorption of oxygen is rigorously in proportion to the degree of activity of the chemical element. For instance, if we cut all the veins which are distributed to a muscle, all volun- tary contraction becoming for it now impossible, the arterial blood traverses it, losing only a small part of its oxygen, and it is red when it passes into the veins (Ch. Bernard), But if 1 Longet, Traité de Physiologie, t. I., p. 581. 70 BIOLOGY. [Boox 1, afterwards, exciting one of its nerves by an electric current, we contract the muscle, immediately a certain consumption of oxygen responds to the contraction; in the passage the globules are charged with carbonic acid; they grow black; they become venous, Analogous phenomena are observed for the same reason during the hibernal sleep, during syncope; and the case must be the same for the blood traversing the veins during dreamless slumber. Claude Bernard has shown that we can produce at will the changes of coloration in the blood by the section and the excita- tion of certain nerves. Essentially in all these special cases of organic atony, there is a general phenomenon: the inaction or the diminished action of the tissues, and of the organs; hence the superabundance of oxygen in the blood. We see therefore that in a certain sense we only need to determine the absorption of oxygen by a tissue to measure the degree of its functional activity. The exchange of gas between the tissues and the globules is probably accomplished by osmosis and diffusion. We must nevertheless remark that in all likelihood the oxygen is in the state of combination with the substance of the globule and the hematoglobuline. In effect, an organic acid, the pyrogallic acid, which is greedy of oxygen, and absorbs it with special ease and eagerness when it is in soltition in the alkaline liquids, succeeds not however in despoiling thereof the globules of the blood. These globules indeed have for oxygen such affinity, that in the arterial blood they absorb it almost in totality, and rob thereof almost completely the plasma. Like all chemical phenomena, the combination of the globules and of ‘the oxygen is influenced by the temperature. At a low temperature it ceases to be accom- plished :—for instance in the body grown cold of a mammifer in the state of hibernal sleep. On the contrary, when the temperature rises, the fixation of the oxygen becomes easy, proceeding as far as 40 to 45 degrees, [Centigrade scale.] Beyond that point the oxydation of the globules tends to Cuap. vi.] OF LIVING LIQUIDS. 71 exaggeration: there is stable combination, something analogous to what takes place when the globules are in contact with the oxyde of carbon, their special poison : the globule then loses its precious osmotic qualities ; it is killed. 6.—Of the White Globules of the Blood. The white globules of the blood, or leucocytes, are pale spherical globules, sarcodic, amceboidal, having a diameter of 0™™, 008 to om, 014. Water and acetic acid pale them and enable us to perceive from one to four granulous masses or nuclei, In the foetus the substance of the leucocyte is less dense, and not granulous; we see therein one or two granulous nuclei. We find also in the blood free or globuline nuclei from 0™™, 003, to 0™™ 005 in diameter, granulous, without nucleoles. In the blood of Man they are in.the proportion of about 1 to 300 red globules : but we meet with them in greater number in woman (1 to 250). They are the more numerous the younger the person is. From one to two yearsold . . . . 1 in 100 Newborn children . . . . . . . 1 in 100 to 130 Humanembryon ...... . lin 80 to 100 We thus see that in relation to the number of leucocytes the woman takes position anew between the man and the infant.? 1 The proteic matters of the globule differ completely from the surrounding fibrine. They have even their special inorganic compounds. The alkaline phosphates predominate in the globules, and have especially a potassic base. In the serum, soda and lime hold sway. The globule contains ten times more phosphates, two times less chlorure, ten times more potash, and three times less soda, lime, and magnesia than serum. We likewise behold the predominance therein of fats, especially of phos- phorised fats, analogous to those of the nervose substance. Lastly, we know that the iron contained in the blood ig entirely confined to the globules. Besides, the substance of the globule, though albuminoidal, is erystallisable. (G. Sée, Du Sang et des Anémies,) 2 Ch. Robin, Des Humeurs. 72 BIOLOGY. [Boor 1 Sometimes the leucocytes are in considerable number in the blood, to which they communicate a greyish tint or the tint of wine lees. Their number in such cases attains and even sur- passes the infantine and embryonary proportion. It is important to remark that in such instances of leucocythemia, there is generally a swelling either of the liver, or of the spleen, or of the lymphatic glands. The leucocytes are not met with merely in the blood: they are also found in the living plasma, which we have yet to study, in the lymph, and then it is observable that they are more numerous in that liquid when it is examined beneath the lymphatic glands. Lastly the leucocytes float in variable numbers in most of the humours of the economy. We can view them in relation to the granulous corpuscles existing so numerously in pus. However, in these last globules the ameboidal movements are less evident, and the nuclei not so easily seen. The leucocytes are met with in the blood of all the mammifers and also in that of birds, of reptiles, and of fishes. However, while the red globule is peculiar to the vertebrates, the white globules, on the contrary, exist also in the invertebrates. _We have signalised the presence of the leucocytes in pus; but we also find them in the blastema of cicatrices, in what is called the plastic lymph. . i We can only make conjectures more or less plausible on the office of the white globules. Peradventure we may regard them as a transitory, primitive, state of the red globules. We know in effect that the first embryonary globules, those which we cannot help regarding as the first pattern of the red globules, are nearly colourless, like the white globules, that like them they have a nucleus, and lastly, that certain inferior verte- brates have only colourless globules. The abundance of the . leucocytes in the blood of the mammiferous embryon comes also as a confirmation of this hypothesis. If this manner of regard- ing the subject had a solid foundation, then by bringing into Cuar. vi.J OF LIVING ‘LIQUIDS. 73 fellowship with it the presence of the leucocytes in the lymph, their greater number after that this lymph has passed through the ganglions, the swelling of these ganglions, either of the liver or of the spleen in leucocythemia, we should be tempted to consider these glands and these ganglions as the original sources, as the centres of creation of the sanguineous globules, which before taking the red tint, before growing retractile, to assume the form of hematia, begin by being leucocytes. In leucocythemia there would seem to be a superabundance of globular formation, while these elements are more voluminous, blended with a great number of free globulines. Hence the difficulty of their transformation into red globules. 7.—Of the Lymph. It is a familiar fact that besides the grand circulatory system, composed of arteries, of veins, in which a propulsive organ, the heart, drives incessantly the blood on, there exists in the superior vertebrates a second circulatory system, without central organ of propulsion. This system, composed of an immense and fine network, which is bestrewn with special glands, called ganglions, has its origin partly in the mechanism of the tissues, and especially on the surface of the membranes, partly around the thinnest sanguineous vessels, the capillaries. In this lymphatic system circulates slowly a yellowish, transparent plasma, convey- ing white globules, and containing, like the blood, immediate principles of the three classes: it is the /ymph. The materials of the lymph come, in chief part, like those of the blood, from anatomical elements, and they come from them likewise by osmotic process. The portion of the network clothing the stomachal and intestinal mucous membrane absorbs direct the nutriments, and especially the emulsionized fats, which, during digestion, give it a lacteous tint. The lymph is not borne on in an endless circuit like the blood. In effect the whole system ends, in man, in two principal trunks, 74 BIOLOGY. [Boox 1. throwing itself into two huge venous vessels, the right and the left subclavian veins. The lymphatic plasma, so analogous to the sanguineous plasma, acts exactly like it when drawn from the vessels. There is evolvement of plasmine and the formation of a fibrinous clot. Like the blood, the lymph is alkaline. It contains nearly the same immediate principles, but in smaller quantity, and more diluted. As its course is very slow, a result is that it has not everywhere, like the blood, a composition observably uniform. On the contrary, this composition varies with every region, with the hour of digestion, and so on. In general the lymph is the more charged with substances, the nearer our examination extends to its chief trunks of communication with the sanguineous system. ; In the mammifers the lymph is a liquid essential, indispensable to the duration of life. If in these animals we form a fistula in the largest lymphatic trunk, the thoracic canal, the lymph being no longer able to blend with the blood in sufficient quantity, we see the patients rapidly grow lean and die, even while continuing to take food. What is the special province of the lymph and of the lymphatic circulation? This is still a very obscure point of physiology. Evidently the lymphatic is an adjuvant of the circulatory system ; it connects the immediate principles in the digestive system and in the mechanism of the tissues, then pours them into the whole grand circulation. Its special function the most probable is to form white globules and to convey them to the great sanguineous current. The fact thata fistula of the thoracic canal is followed by death, proves conclusively that the lymphatic: system is not a mere ornamental apparatus, and that it plays in the economy one of the most important parts. BOOK II. OF THE PRIMORDIAL PHENOMENA OF LIFE. CHAPTER I. OF NUTRITION. We cannot form a precise idea of the mechanism of nutrition, unless we have thoroughly present to our mind the general laws of diffusion and those of osmosis, especially between crystalloids and colloids. We know that two solutions of different density, put separately into a diffusion vessel and consequently in contact only on a small surface, mingle by degrees intensely, to such a point indeed that after a given lapse of time, the blending has everywhere an identical composition. We also know that every substance has a degree of special diffusibility, and that generally the colloidal substances have a diffusibility infinitely inferior to that of the erystalloidal substances. A glance at the following table furnishes a complete idea of this difference :— QUANTITIES DIFFUSED IN EQUAL TIMES. Chlorure of Sodium . ... . . . 58,68 Sulphate of Magnesia . . . . . . 27,42 Nitrate of Soda . . . . « « = ~ 51,56 76 BIOLOGY. [Boox 11, Sulphuric Acid. . 2 1. 1. (69,82 Sugar Candy . fo ed ee os 26,74 Barley Sugar. . woe ee e « 26,21 Molasses of Cane — woe ew we 89,55 Sugar of Starch . . . . . « . « 25,94 Gum Arabic. . . . 2... ee (18,24 Albumine . . .. -.. s+ 8,08 Furthermore, these colloids, so slow to blend and to be diffused are easily penetrated by the crystalloids, while their analogues cannot traverse them except by taking, through isomeric modifica. tion, an altogether special state of solubility. For instance, we shall see when speaking of animal digestion that the albuminoida. substances of the elements, in order to pass into the circulator) system, need previously to be transformed into soluble albuminose We must also. remember that two substances, incapable o: chemical combination, and possessing different degrees o: diffusibility, separate to a certain point, when they are put iz a blended state, in a diffusion vessel, for then the more diffusibk of the two passes out more rapidly than the other. The application of the preceding data to nutrition is achievec almost of itself, so to speak. In effect, from the simply physica point of view, organised beings are merely masses of colloida substances, holding in solution crystalloidal substances. Thii definition is strictly true for a number of rudimentary organisms for instance the amebe and most of the infusoria; in general for all those beings, neither vegetal nor animal, of which: Haecke has made his group’of monera, J+ applies even to a number o zoophytes, and also to every histological element of the superio organisms, isolatedly considered. Let us take the small amorphou mass of contractile albuminoid substance which constitutes ai ameba, a rhizopod, or monocellular beings such as the Protococcu nivalis, many infusoria, lastly the globules of the blood of th mammifers, and even the cells and fibres, grouped into tissues t form the body of plants and of the superior animals; we se Omar. 1.] OF NUTRITION. red that in some, every element living, ultimate, isolated, or associated to other analogous elements is only a small mass of colloidal substance. But like all colloidal bodies, this substance is capable of imbibing water and aqueous solutions; it may be said greedily to seek them; thus there is established in the midst of its molecules an incessant aqueous current, which conveys to them soluble substances, modified crystalloids or albuminoids, and which at the same time seizes back other substances, usually crystalloidal, which have become unfitted to form a part of the living body. The phenomena of diffusion however are not by any means peculiar to the liquid state. In a gaseous medium the diffusion of liquids is simply replaced by gaseous diffusion direct or indirect. We have seen besides that analogous phenomena are produced even in the midst of living liquids, in the blood and the lymph of the superior animals. But if the physical condition of nutrition is simple diffusion in amorphous beings not yet composed of cells or of fibres, it is a little more complex in the others, if we proceed from the monocellular organisms to the superior mammifers, constituted by fibres and cells cemented or groupedin tissues. Here the diffusion is accompanied by the passage of the liquids through a membrane, that is to say, that there is osmosis, and naturally osmosis with a double current from without to within, and from within to without, endosmosis and exosmosis, We must needs do for osmosis what we have done for diffusion, that is to say, briefly recall the principal facts appertaining thereto. Osmosis, discovered by Dutrochet,! then studied especially by Graham, who gave it the name of dialysis, is, ‘as is well known, the blending of two unequal densities, separated by a membrane. Definitively it is diffusion in special mechanical conditions, which permit the superposition of the liquids, whereby 1 J.-B. Dutrochet, De U’Endosmose, in Mémoires pour servir d 0 Histoire. anatomique des Végétaun ct des Animaum, t. I. Paris, 1837. 78 BIOLOGY. {Book 11, for instance the more dense can be placed above the less dense, As essentially there is a very gréat analogy between diffusion and osmosis, it follows as a matter of course that the substances which osmosis finds the most sluggish must be the colloidal substances ; and that is exactly what experience confirms. In osmosis, the membranous partition, usually organic, which separates the liquids, is' traversed simultaneously by a double current ; and commonly the stronger current goes from the less dense liquid to the more dense liquid. There are however exceptions. For instance, if water and alcohol are separated by, a fragment of bladder, the water passes in greater quantity towards the alcohol. It has been supposed that in this case the direction of the current depends on the inequality of the capillary attractions between the liquids and the two faces of the membrane. The water moistening the membrane better than the alcohol, rises by capillarity in its pores, while on the contrary if we substitute for the bladder.a layer of collodium, which is better moistened by the alcohol than by the water, the direction of the osmosis is reversed. All the membranes with which osmotic experiments have been made are in effect really and thoroughly perforated (bladder, collodium, paper, parchment, and so on). But this explanation does not suit all cases, and especially the cases of osmosis through living liquids. In effect, so far as our most powerful microscopes permit us to assure ourselves thereof, the surfaces of the animal and vegetal cells and fibres are absolutely homogeneous. ‘We find no trace of pores. No doubt we are compelled to admit molecular and atomic intervals across which thé passage of the solutions must be effected ; but in this case the osmosis is accompanied by a chemical action exercised on the dialysing membrane. The liquids, gases, or vapours, which traverse the cellular or fibrillary walls unite themselves, as they pass along, molecule by molecule, to the chemical elements constituting this wall; then, as on the other side of the membrane they find themselves in contact with a new fluid, they forsake forthwith the elements of the wall to combine with those CuapP. 1.] OF NUTRITION. r 79 of the fluid which they encounter. This explanation, proposed by M. Ch. Robin, would, if well founded, furnish an explanation. of an extremely important fact. It would make us understand why in the organisms themselves the composition of the fluid absorbed is no longer on the hither side of the membrane or living wall what it was on the thither side; a phenomenon peculiar to the biological osmosis, and never produced in the endosmometers and the dialysing apparatus. But, well founded or not, this explanation seems to me by no means needful to furnish a reason for the changes occasioned in the composition of the fluids by physiological absorption, It suffices to explain this metamorphosis to take into account chemical phenomena at the same time as physical phenomena. Hitherto almost all the osmotic experiments effected in the laboratories have borne upon liquids miscible indeed, but exercising on each other no chemical action. Obviously this is not what happens in the living tissues. There the fluids which have traversed a living wall hold in solution unstable substances, which are by the very fact of the osmosis in contact with other fluids composed of substances of analogous complexity and of different composition. There are evidently at the time of this conflict, exchanges of molecules, chemical reactions; the new substances arising repair the waste of the old, and for that purpose are forced to enter into alliance and combination with them. The residuum of these functions and that of the waste of the substances previously organised are a blending of diverse crystalloidal bodies, which is promptly dragged away from the histological elements, the fibres, and the cells, to be afterwards definitively expulsed from the organism. We have seen that nothing is easier than to separate with a dialyser a crystalloidal substance from a colloidal substance. It is very evident nevertheless that the cellular wall is not inert in all this labour of molecular mutation. It is as living as that which it contains, and must consequently in like fashion participate in the pkenomena of transformation, 80 . BIOLOGY. [Boox 11. We could surely in osmotic experiments draw much nearer to what comes to pass in the organised bodies by making to react on colloidal substances oxydant bodies, capable of giving birth thus to crystalloidal bodies, and so on. The curious experiments of Traube on artificial cells have taught us that it is possible to imitate in a certain measure the physical and chemical phenomena of life.1_ Assuredly we hither- to are far from having imitated within the domain and the range of the possible, the phenomena of animal physics, and of vegetal physics, which form the essence, the support of the vital acts. No doubt the lack of initiative, which, in regard to this matter, experimentalists have displayed, must in a large degrce be at- tributed to the metaphysical and mystical ideas which have been conceived of life. As long asthe vital phenomena were considered as of an order altogether apart, as having no relation with the physical or chemical phenomena; as long as there was a belief that to explain what was called ‘the miracle of life’’ there had to be invoked directing entities, independent of the bodies, a kind of immaterial gods set over the physiological government of every organism, an archeus, a vital principle, and so on, it was naturally almost impossible that the idea of reproducing arti- ficially the principal physico-chemical acts of life should occur to experimentalists. In our days there is, fortunately, a complete change, and we see men of science venturing on paths which they would never have dreamed of entering half a century ago. M. Traube has based his experiments on two principal facts. The first of these facts has been established by Graham ; it is, that the colloids dissolved are incapable of penetrating by diffu- sion through the colloidal membranes. The second fact is, that the precipitates of the colloidal substances are themselves col- loidal. Starting from these facts, M. Traube has been able, artificially, to make cells, the wall of which was formed of tannate of gelatine. He takes a drop of gelatine, which, by an 1 Experimente zur Theorie der Zellbildung und Endosmose (Archiv fiir Anatomic, &c., von Reichert und Dubois-Reymond, 1867, p. 87). Cuar. 1.] OF NUTRITION. 81 ebullition of thirty-six hours has lost its coagulability. He lets it dry in the air for several hours, and by the help of a rod fixed in the cork of a vessel half filled with a solution of tannin, he plunges it into this liquid. Then the small quantity of gelatine which dissolves on the surface of the drop combines with the tannin, and the result is a closed cellular membrane. But this membrane is homogeneous, unperforated, as the organic membranes are. Also the diffusion which is established between its contents and the exterior liquid must be effected osmotically across the molecular interstices. The osmosis is produced very energetically. The membrane distends more and more; as a consequence the constituent molecules sever from each other: at a given moment when the molecules of the two liquids brought face to face can easily be introduced into the molecular interstices and blend, they form anew molecules of tannate of gelatine. Consequently, the membrane grows by intussusception, In effect, it suffices to arrest all increase, to substitute water for the solution of tannin. M. Traube forms also, in the same manner, endosmotic mem- branes, very curious, impermeable by certain substances, very permeable by others; in a‘word, exercising on the substances in contact with them an elective action, such as the living membranes exercise. ‘ According to M, Traube, every precipitate whose molecular interstices are smaller than the molecules of its components must take the form of a membrane. Lastly, the endosmosis across the membranes depends solely on the attraction of the body which is dissolved for its solvent. These experiments are infinitely interesting; nevertheless, they imitate very imperfectly what takes place in the living célls. It is something to have obtained by simple chemical processes a membrane which grows by intussusception, foras- much as, from time immemorial, this mode of growth has been considered peculiar to living bodies. But in the living cell there is something more ; the contents are as little inert as G 82 BIOLOGY. [Boox 11. the enveloping membrane; they are modified and renewed un- ceasingly, molecule by molecule, without being destroyed. In the primordial phenomena of nutrition there are, in effect, two acts, or rather two principal aspects of the same phenomenon, assimilation and disassimilation. To assimilation relate the facts of absorption and endosmosis ; with disassimilation are connected the facts of secretion and exosmosis. We must remember that disassimilation has, as result, the transformation of the colloidal substances of living bodies into crystallisable substances, occupy- ing, after a fashion, a middle position between organic substances and mineral substances. ; It is now invincibly demonstrated that these primordial facts of nutrition are identical in all the living universe, as well in the animal world as in the vegetal world. It is also known, moreover, that the principal agent of all these transformations, of all these exchanges, is the oxygen of the air. In the most rudimentary beings, amorphous or monocellular, oxygen is diffused direct in the midst of the molecules of the living substance ; it oxydises this substance by a sort of slow combustion, and determines the formation of diverse organic crystallisable bodies, and of a gas—carbonic acid; the whole is afterwards expulsed. In the being whose structure is more complex, where there is an aggregation of cells, of fibres, in a word, of diverse histological elements, each having its special form and special functions, while the whole are, moreover, grouped in particular tissues, the oxygen of the air, and generally all the substances which penetrate ihto the organism and come forth from it, have to undergo a sort of gradatory process before being assimilated or excreted. In the simplest cases when the organism is merely constituted by histological elements of kindred nature, more or less straitly joined together, and bathing in an interstitial liquid, a circulatory — system, a respiratory system, a digestive system being wholly lacking, the nutritive substances and the disassimilated substances dissociate themselves in the intercellular blastema. It is in this Caap. 1.J OF NUTRITION. 83 liquid, impregnated as moreover it is with oxgyyn and carbonic acid gas dissolved, that the histological elements choose the materials which suit them and reject those which are no longer suitable. At a more exalted degree of structure are superadded special apparatus, systems more or less ramified with canals, in which circulate the liquids and the gases. But even then the interstitial, intercellular liquid ceases not to exist; it merely renews, revivifies, purifies itself without pause, seeking suste- nance in the circulatory fluids, and ridding itself there, in its turn, of the substances destined to elimination. In sum, the intercellular liquid acts toward the circulatory fluids as the histological elements act toward itself. We see that it is by a peculiarity of construction that almost all organised beings live in the air. In truth, all the histological elements constituting the complex organisms are aquatic; they bathe in a special liquid, in a living medium, which is alike their essential cause and the result of their nutritive activity. Cl. Bernard has much contributed in these last years to propagate this felicitous idea of the interior media, such as the blood of animals, the sap of plants, and so on: “that ensemble of all the interstitial liquids, that expression of all the local nutritions, that source and confluent alike of all elementary changes.”! We may admit, with the eminent physiologist, though with restric- tions and exceptions for the living beings that are wholly rudi- mentary, that there is no direct nutrition, and that, for instance, the fragment of a fresh-water polypus, when it is reconstituted and completed to the point of re-becoming an entire polypus, avails itself principally of the nutritive interstitial fluid which impregnated at the outset the separated fragment. Thus, for every complex organised being there are three superposed media, the cosmic medium. aérian, or aquatic—but in this last case holding the air in solution; the sanguineous, or sap-filled medium ; lastly, the interstitial, intercellular medium. Naturally, the internal media need, like the external inedia, to 1 Revue Scientifique, 1874. G 2 84 BIOLOGY. [Boox 11. maintain themselves in what we call a suitable state of purity, that is to say, in a state of composition sufficiently equilibrated for the histological elements to find therein at every instant their food. We shall see in the course of this exposition that in the complex organisms special apparatus of exhalation, of secretion, and of excretion are charged to keep up incessantly across these media renovating currents, exactly as other apparatus, for instance, the digestive apparatus and certain glands, pour in suitable nutriments. These general data accepted, we can now analyse the acts, the phases of nutrition. We know that this biological property exercises itself in all living substances, figurate or not, as well in the plasmas and the blastemas as in the figurate elements. In both it depends in part on. physical conditions of endosmosis, exosmosis, and diffusion, and in part on the physical affinities of substances brought into relation. In all this there is not the smallest place for a metaphysical agent. We have simply to do with physical and chemical phenomena producing themselves in conditions of complexity and simultaneousness entirely special, yet narrowly bound to the variations of the ambient medium. We see in effect these phenomena intensified or enfeebled acvord- ing as the air is more or less oxygenised, according as the temperature is higher or lower, and so on. Though the nutritive phenomena are simultaneous and unin- terupted, we can, for the convenience of exposition, divide them into phenomena of assimilation and phenomena of disassimi- lation. It is by endosmosis that the immediate principles reach the substance of the anatomical elements, reach the living liquids. The principles of the first class, that is to say, the mineral substances, often arrive without modification by simple dissolution, and it is thus, for example, that the chlorures and the alkaline sulphates arrive. Certain of these substances combine with the organic matters, as, for instance, the phosphate of lime com- bines with osseine'in: the bones ; but then, in opposition to the . Cuap. 1.] OF NUTRITION. 85 laws of non-living chemistry, the combination does not seem to be accomplished in definite proportions. It is a sort of alloy. In plants the power of assimilation seems more energetic. It is in the mineral medium, in effect, that the plant must seek its aliments direct; consequently we see the green parts of plants assimilate at once the carbon of aérian carbonic acid, and incorporate it immediately with complex organic substances, ternary and quaternary. The same synthetical power is exercised in certain circumstances on the azote of the air, and, normally, on the azote of the ammoniac salts drawn by the roots of plants from the soil. In the animal, the true phenomena of assimilation are generally exercised at the expense of albuminoidal substances already elaborated. It is an important and remarkable fact that the organic assimilated substances have never, previously, the same composition as those which form the assimilative anatomical elements. The musculine, the elasticine, and the like, peculiar to every species of cell, of fibre, and so on, are, in effect, met with, nowhere apart from the elements which they constitute and reconstitute incessantly ; they are formed in the animal organism at the expense of the living liquids, by isomeric catalyses.' The anatomical elements can assimilate a great number of substances, but they have necessarily their own special affinities, entirely analogous to those of the bodies of mineral chemistry. Thence result a choice and a selection, which, for a long time, appeared intelligent, though here intelligence no more enters than in the affinity of chlore for hydrogen, of anhydrous sul- phuric acid for water, and so on, These chemical combinations formed in the substance of the anatomical elements have excessive instability, and they are the more unstable the more life rises to a superior degree, the more it is animalised. Thus chemical instability is much greater in the anatomical animal elements than in the vegetal elements.? In these last we cannot dissever 1 (Ch. Robin, Anatomie Microscopique des Bléments Anatumiques. 8vo. Paris, 1868. 2 Ch. Robin, loc. cit. p. 65. 86 BIOLOGY. [Boox 11. the chemical combinations but by the aid of energetic chemical agents. Moreover, it is much less easy to interrupt the vital movement in the plant than in the animal. But in them both, chemical instability, in various degrees, is the very condition of life, Every combination too stable is the equivalent of death. Nutritive assimilation has naturally, as a condition, a corre- sponding disassimilation. In order that new substances may incorporate themselves with an anatomical element it is abso- lutely necessary that other substances yield their place to them. In effect, incessantly a portion of the substances which formed part of the anatomical element ceases to resemble the fundamental substances, and severs itself from them. The substances thus have not, by reason of the severance, ceased to be complex albuminoidal substances, but generally they have become more oxydised, and have passed into the state of crystallisable matters, —they have taken a step to return to the mineral world. As to the mineral substances expulsed from the anatomical element, certain of them merely pass through without undergoing any change. This is the case with sundry salts, azote, water, and so on. Other mineral compounds, however, are formed therein by direct combination, just as they would have been formed in a retort. In this fashion are produced in animals, the alkaline carbonates, the lactates, the ammoniaco-magnesian phosphates, the phosphates of lime, the urates, carbonic acid, and so on. The nutritive exchange is not effected in all the tissues with the same energy. In general it is in the cell, properly go called, or in tissues formed by cellular aggregations, that this double current attains its maximum of power. Nutrition can often be effected without the succour of special circulatory apparatus. The exchange of nutritive materials frequently is achieved in this case from step to step with sufficient rapidity. Things take place thus in certain inferior organisms simply polycellular, in the crystalline of the eye of mammifers, and so on. Cuar.1j ° OF NUTRITION, 87 If a tissue is at the same time constituted by cells and furnished’ with a rich vascular network, it is in conditions specially favour- able, and the nutrition thus is rapid and energetical: this is what takes place in the mammifers, in the medullary tissue of the bones, in the grey substance of the brain, and so on, After the exposition of the general facts to which we have devoted this chapter, it will be now more easy for us to present successively in the two organic kingdoms the history of nutrition, that is to say, of the vital property which is the support and the essential cause of all the others, CHAPTER II. VEGETAL NUTRITION. In the composition of every plant we find mineral substances, ternary substances non-azotised and proteic substances. Now plants not eating each other direct, like animals, it is needful for the vegetal organic substances to be habitually created by the plant itself, at the expense of the mineral medium which environs it. Brought back to their primary mineral elements, the complex organic substances yield carbon, oxygen, hydrogen, azote, and a certain quantity of sulphur and of phosphorus. If we add to these elements chlore, calcium, silicium, potassium, sodium, magnesium, lithium, iron, often manganese, and in the marine plants, iodine and brome, we have nearly the whole elementary sources of alimentation in the vegetal kingdom. Naturally the metals which we have just enumerated form bases which combine with the acids which they encounter, to consti- tute sulphates, silicates, chlorures, often organic salts, for instance, oxalates, and so on. To form a sufficient idea of vegetal nutrition, we must follow these mineral elements, note how they enter into the plant, indicate the combinations which they form there, finally, leave them only when, having played out their part in the vegetal organism, they are finally expulsed from it. Of these chemical elements, some, for example, are derived from the air, others from the soil. The mineral elements taken direct from the ambient air by the plant are hydrogen, oxygen, carbon. Hydrogen and oxygen are absorbed and fixed by the Cuap. 11.] VEGETAL NUTRITION. 89 plant, either simultaneously in the state of water, or isolatedly. It is probable, in effect, that the green parts of plants have the power of decomposing water, which they draw in a small part from the atmosphere, but in enormous quantity from the soil. The chlorophyllian parts would effect the decomposition of water, whatsoever its source, and would fix direct its elements in the complex combinations of which we have spoken. This, however, is a point which has not yet been well studied. Certain, at least, it is, that the greater part of the oxygen absorbed by the plant is taken from the atmosphere direct, and a little by all parts of the vegetal organism. As to carbon, which forms in weight the chief part of every desiccated plant, it also is derived by the green portions of the plants from the carbonic acid of the air. This is one of the most interesting, one of the best studied points of vegetal physiology. All the other mineral matters, and almost the whole of the water, are absorbed by the roots of the plant, penetrate into the vegetal tissues, there ascend, there meet with, especially in the leaves, the mineral substances derived from the air, and some of them form complex combinations. Vegetal physiology is still so confused, the division of labour in the plant is so ill-distinguished, that it is not easy to mark out therein functions thoroughly determinate, functions very dif- ferent from each other. Everything is connected, everything blends, everything forms the link of a chain, Nevertheless, for clearness of exposition, we are obliged to make divisions more or less natural; we must, in effect, speak of phenomena mingled, entangled, proceeding sometimes simultaneously in the same tissues or organs. We have to tell how penetrate into the plant the numerous mineral substances which chemical] analysis discovers there, how those substances have infiltrated themselves into the tissues, what compounds they have formed there under the powerful action of the nutritive movement, finally how and in what proportion they were eliminated during the life of the plant after becoming unsuitable to figure in the nutritive process. $0 BIOLOGY. [Boox 1.. 1. Formation and Circulation of the Sap. Let us take as type a complete plant, a dicotyledon, plung- ing its roots into the ground, displaying its branches in the air. In the spring such a plant impregnates itself incessantly with the materials which it appropriates from the exterior medium. It absorbs them by the roots, by the leaves, by the bark. It is by the osmotic process that the roots draw from the soil the — first materials of the sap. It is the delicate cells of the extremities of the roots, radicellular spongioles, which are the principal agents of absorption. These cells contain a pro- toplasm dense and albuminous, coagulable by nitric acid; they are in contact with the soil by means of their cellular - membrane, by means of the hairs which garnish them; they are thus in conditions very favourable to osmotic absorption. It is, moreover, easy to prove that is owing to the process entirely physical of endosmosis, that the roots saturate themselves with the humidity of the soil, for all that is needful to arrest their work of absorption is to plunge them in a saccharine and dense solution. In the soil, on the contrary, the water, relatively little charged with dissolved substances, moistens the extremities of the roots, penetrates by endosmosis into their anatomical ele- ments, and mingles there with their protoplasm, bringing with it ammoniac salts, phosphates, salts of potash, and so on. But to accomplish their office the hairs of the roots need, like all organised cells, nourishment, that is to- say, need to be oxydised, to absorb oxygen, and to exhale carbonic acid. Con- sequently, the penetration of the air into the soil into which. the roots plunge is indispensable to the maintenance of the life of plants. The exhalation of the carbonic acid by the roots has also its utility. In effect it is from the presence of this carbonic acid that certain salts become soluble in water and can thus penetrate into the radical cells. The case is the same, for example, with certain phosphates, and no doubt also for silica, and soon, Once. introduced into the cells of the spongioles, of Crap. IL] VEGETAL NUTRITION. 91 the radical hairs, the substances, borne on by the water which holds them in solution, pass from cell to cell, each borrowing . from each, in proportion as the nutritive waste goes on. In plants with roots, this ascensional movement of the liquids drawn from the soil is facilitated by the presence of those vessels and vascular bundles we have previously described; there are indeed no roots except in the plants whose cellular tissue is traversed by vessels. In the spring the flow of the sap is so abundant that it invades everything ; cells, fibres, vessels, even the interstices of the cells or intercellular meatus. This flow thus ascends from the root to the leaves, but circulates more rapidly in the vessels, where it encounters fewer obstacles, and is, in a certain measure, raised by capillarity. The grand movement of ascension is accomplished through the central part, through the ligneous body, or through its exterior zone, younger and less incrusted if the vegetal is already aged: Very certainly multiple causes, endosmosis, diffusion, capillarity, the nutritive fixation of the alible materials in the buds, evaporation on the surface of the leaves, co-operate in the ascension of the sap; but the most powerful cause is assuredly the absorption exercised by the ascensional cells of the roots. In effect a plant can live and ac- tively live when its radical extremities alone are placed in water. Besides this grand general movement of the sap there are others more interesting perhaps, those, namely, of the contents of the cell, of the protoplasm. This liquid, which we know to be habitually an albuminoidal liquid, is granulous, and we see in nearly all plants its granulations execute along the walls of the cell or of the fibro-cell a gyratory movement. They mount on one side and re-descend on the other. This protoplasmic movement is a vital movement connected probably with the molecular exchanges and reactions of nutrition. It is accom- plished only within determinate thermometrical limits. The minimum limit approaches 0 degree, the maximum limit is from 45 to 47 degrees. It is toward 35 to 37 degrees that the speed of the protoplasmic current attains its maximum, When it is the 92 BIOLOGY. (Boox 11. cold which arrests this gyratory movement, we can by beating the soil put the liquid again into motion.! With respect to this manifest action of heat it is curious to see that light seemingly influences little or not at all the pro- toplasmic movement which is accomplished without apparent modification even when the plant is kept in darkness. After gyrating in the cells, travelling in the vessels and the meatus, after taking from or giving to the elements, which it has traversed or passed beside, certain of the matters which it conveys, the sap arrives at the part truly aérian of the vegetal. There it undergoes very important modifications, thanks to the special action of a substance of which we have now to speak. This substance is the green matter of the leaves, the chlorophyll. 2.—Chlorophyllian Property. Chlorophyll is the substance to which all the green parts of plants owe their colour. In the cells of certain lichens and of certain alge, the chlorophyll sometimes presents itself in the amorphous state, colouring all the protoplasm, sometimes in irre- gular masses; but habitually in all the vascular plants it has a definite form, that of green granulations of from 0™™, 001 to o™", 005 in diameter, of homogeneous appearance and without nuclei. Wecan obtain from this green matter fat crystallisable bodies, stearine, margarine and so on, and an immediate azotised principle, chlorophyll properly so called, the elementary analysis of which gives oxygen, hydrogen, azote, carbon, and iron. By an appropriate chemical treatment Frémy was able to separate chlorophyll into two substances; the one yellow, phylloxanthine, and the other blue, phyllocyanine. Chlorophyll rises spontaneously in the cellular protoplasm. First of all are formed colourless or yellow particles, which grow green afterwards, if the cell in which they are contained is exposed to the light. The chlorophyllian particles, born in ' Nageli, quoted by Sachs, Traité de Botanique,.pp. 855, 856. CuaP. 11.) VEGETAL NUTRITION. 93 the darkness, remain yellow, but under the action of even a feeble light and a somewhat elevated temperature, of from 20 to 30 degrees, they grow green. All the rays of the solar spectrum suffice to make the colourless chlorophyllian particles green, but by far the most active are the yellow rays. Once formed, the chlorophyllian particles, if they are favoured by good conditions, increase in size, and at a given moment can multiply by binary division. The solar light does not merely influence the formation of the chlorophyllian particles; their whole evolution is subjected thereto. The particles veridified and subjected to an intense light during a long space of time form in their very substance particles of starch, which are most manifestly the result of a nutrition too active, an aliment in reserve. This starch besides re-dissolves and re-forms according as the green cell is withdrawn from the solar light or exposed to it anew. From a long sojourn in darkness the particles of chlorophyll themselves lose their shape, suffer atrophy, and disappear, dissolving into the colourless protoplasm. We have seen that all the rays of the solar spectrum have the power to render green the chlorophyll; but all are not capable of impressing on it enough of nutritive activity to form the starch in its particles. That is a faculty limited naturally to the rays the most stimulating, the yellow rays. Light being the determinating agent of the chlorophyllian formation, it is. natural for the chlorophyllian particles to accumulate specially on the best illuminated cellular wall; and this, in reality, is what takes place. In the persistent leaves, heat appears to have a great influence on the position of the particles of chlorophyll. -In effect, when the temperature lowers they quit the wall to accumulate inter- volved in the centre of the cell. In spring, or whenever the plant is subjected to a certain elevation of temperature, they, whether in darkness or in light, resume their parietal position. Lastly, toward the end of the vegetative period, the precious 1 Franck, Botanische Zeitung, 1872. 94 BIOLOGY. [Book 11. t chlorophyllian substance in a great measure escapes destruction - in the perennial plants. It re-dissolves along with the starch ‘which it englobes, and the whole, passing through the petiole, » and carrying along even the phosphoric acid and the potash, wanders toward the permanent organs of the plant.! Before we speak of the special properties of chlorophyll, it is opportune. to signalise the importance of the metallic element which it contains. The atoms of iron which enter into its com- position constitute m effect an integrant part of it; without them itis not endowed with its special properties. Another metal, potassium, though not figuring in the complex molecule of the chlorophyll, seems to play an important part in its nutrition, When the plant does not absorb chlorure of potassium, or at least nitrate of potash, the particles of chlorophyll have less vitality and are incapable of forming starch. We have succinctly described the morphological evolution of chlorophyll. It remains for us now to speak of its function. Priestley was the first to observe that the green parts of plants exhale oxygen. He put under a receiver in confined air, where mice had died asphyxiated, some mint plants, which lived and flourished energetically there. The chlorophyllian property was thus discovered ; but it was Ingenhouz who attributed the disengagement of vital air operated by plants to its true cause, the action of light. The same observer demonstrated also the inverse action of the flowers and of the roots, which night and day exhale carbonic acid and vitiate the atmosphere. Every terrestrial or aquatic plant furnished with chlorophyllian cells, and exposed to the solar light, borrows from the air carbonic acid, and restores to the air an equivalent volume of oxygen. For most plants, the activity of the phenomenon is in proportion ° to the intensity of the light. Though the chlorophyllian function : has need in almost all plants of full light, it still exercises itself, feebly indeed, in diminished light, and there are even 1 J. Sachs, Traité de Botanique. 2 Ingenhouz, Expériences sur les Végétaux, 1780. Cuap. 11] VEGETAL NUTRITION. 95 plants, mosses, for example, living in the shade of the woods, which cannot, without dying, bear an intense light. But in diverse degrees, light is indispensable to the green parts of all plants, At night, or in darkness, chlorophyll ceases to act, and the plant simply exhales carbonic acid. The property of decomposing the carbonic acid of the air and of absorbing carbon specially appertains to chlorophyll, just as that of fixing a great quantity of oxygen specially appertains to the hemoglobuline of the hematia. Chlorophyll has also, like hemoglobuline, its poisons. Thus, as Boussingault has demon- strated, mercury introduced into a receiver where a plant is destroys the chlorophyllian property. It seems to result from the experiments of Dutrochet,! that a part of the oxygen put at liberty by the chlorophyllian action is not immediately expulsed, but penetrates previously into the mechanism of the tissues. The oxygen exhaled direct is merely air overplus. The rest is impelled into the aérian cavities, into the globulous vessels, into the punctuated tubes, and especially into the trachee. In this way it descends into the petioles of the leaves, into the stem, and serves there probably the real respiratory function, the oxydation of the tissues, and the production of the carbonic acid disengaged by the plant. It is by the stomata that this expulsion and this absorption of air seem especially to be accomplished ; nevertheless, the mosses and the conifers, which have no stomata, exhale carbonic acid. We might be astonished that the small proportion of carbonic acid contained in the air suffices for the alimentation in carbon of the whole vegetal kingdom, if we did not think on the great density of the atmosphere, and on the considerable restitu- tions that are made to the atmosphere by the vegetal kingdom on the one hand, and by the entire animal kingdom on the other. This last, in effect, incessantly consumes oxygen, and exhales torrents of carbonic acid. Moreover, we must add to these principal sources of carbonic acid all the combustions, the 1 Dutrochet, De ?’Endosmose, p. 357. 96 BIOLOGY. [Boox 11. volcanic exhalations, and so on. As to the rest, in calculating in accordance with the presumed height of our atmosphere and the proportion of four ten-thousandths of carbonic acid for a given volume of air, we arrive in estimating the quantity of carbon existing in the aérian medium at the enormous figure of 1,500 billions of kilogrammes, It is also probable that the air is not the only source of the carbonic acid absorbed by the plant. There is assuredly some produced by the oxydation of the sap and of the anatomical elements, and there is no reason for supposing that the plant does not also undergo the decomposing action of the chlorophyll, As the carbonic acid is, when light acts, incessantly de- composed by the chlorophyll, there results a sort of carbonic void in the portion of the air in contact with the green cells, and consequently by degrees and by diffusion new quantities of acid arrive. The alimentation in carbon is therefore never lacking. . Though the decomposition of acid is effected in all the green cells, nevertheless, the upper surface of the leaves seems to play the predominant part in the chlorophyllian act, for if we turn the leaves so as to expose to the sun their under-surface, the carbonic action diminishes, and in a few days ceases.? Let this be as it may, the exhalation of carbonic acid, little perceptible during the day and relatively active during the night, is far from compensating the absorption. M. Boussingault has calculated that in twelve hours of the night one square deci- metre of green surface burns 0%,214 of the carbon of the tissues, while in twelve hours of the day it assimilates 3*,416. If we allow the light to reach plants, only by allowing it to pass through glass coloured with the colours of the prism, we see that all the visible rays-can put chlorophyll into activity, but that the rays capable of exciting its appearance in the protoplasm are also those which stimulate chlorophyll most: These are, in effect, the yellow rays, which determine the most abundant disengagement of carbonic acid. 1 Dutrochet, De Endosmose, p. 355. Cuap. 11.] VEGETAL NUTRITION. 97 If we attentively regard the undulatory amplitude of the luminous rays suitable for making the chlorophyll operate, we see that those active rays have as highest limit 0",0006886, and as lowest limit 0",00039968. They are rays feebly refrangible.! The rays most strongly refrangible, the blue and the violet, as well as the ultra-violet invisible rays, influence especially the rapidity of growth, the movements of the protoplasm and of the zoospores, and so on. We have recently compared, in passing, chlorophyll and the hematoglobuline of the blood. The parallel is so curious that we must consecrate a few lines to it. Chlorophyll and hematoglobuline are both quaternary sub- stances. They both exercise an elective action on a mineral gas. They both are habitually moulded into globules, without nucleus, The special property, however, which characterises them seems in both to be independent of the form which ‘they assume. We have seen that a solution of hematoglobuline absorbs oxygen, and that amorphous chlorophyll, dissolved in the cellular proto- plasm of certain plants, continues, nevertheless, to absorb molecules of carbon. Chlorophyll and hematoglobuline equally seom to form only a temporary association with the mineral element which with special avidity they seek. In effect, the sanguineous globules yield to the anatomical elements of animals their provision of oxygen almost as soon as they have taken it, and, in return, they charge themselves greedily with carbonic acid, thus holding kinship with the chlorophyllian globules in this aspect of their physiology. Chlorophyll, though absorbing, like every living substance, the quantity of oxygen necessary to its nutritive movement, does not seem to have a great affinity for that gas. It is probable that in the night it ceases purely and simply to exercise its special action without assuming another; but it is certain that it does 1 J, Sachs, Traité de Botanique, p. 878. ' H 98 BIOLOGY. [Boox 1. not fix more than for a moment the carbon derived from the carbonic acid. As this carbon does not accumulate in the chlorophyllian tissues, as the composition of chlorophyll is always perceptibly the same, the molecules of carbon assimilated by it must be instantly surrendered to the sap to which they bring the supply needful to the formation of complex substances, ternary and quaternary. Whence, besides, could the tissues take the carbon which constitutes the half of their weight, if they had not, to provision themselves, this perpetual supply? We shall have some words to say on this living chemistry. Let us occupy ourselves for the moment with the vegetal function, comparable in everything with what is called respiration in animals, that is to say, with the absorption of oxygen. 3. Absorption of Oxygen or Vegetal Respiration. A green phanerogamous plant is asphyxiated in a medium of hydrogen, of azote, and even of carbonic acid, and if its sojourn in this artificial atmosphere is too prolonged it loses for ever the chlorophyllian property.! Besides, M. de Saussure had already remarked, when extract- ing by the aid of a pneumatic machine the air impregnating the tissues of plants, that this air contained notably less oxygen than the ambient atmosphere. The proportion is very variable; that found by Saussure was 85 of azote and 15 of oxygen? Moreover it has long been known that during the day when in darkness, and consequently during thé night, plants disengage carbonic acid. Ingenhouz had already observed that this dis- engagement of carbonic gas was constantly operated by flowers and roots. Finally, in our own day, Boussingault, Garreau, Sachs have been able to demonstrate that this exhalation isa permanent and general fact, that it is effected even by the leaves exposed to the sun. In truth we have here to deal with an act indispensable to everything which lives. Without this continual 1 Boussingault, Annales de Chimie et de Physique. IVe série, 1868, t. XIII. 3 Th. de Saussure, Recherches Chimiques sur la Végétation. 1804, Cuap, 11] VEGETAL NUTRITION. 99 labour of slow oxydation organised substances could not accomplish their metamorphoses, operate the exchanges of matter which constitute the fundamental act of life. : As Dutrochet said in reference to this point: “ Life is one ; the differences are not fundamental, and when we follow the phenomena to their origin the differences disappear.” This absorption of oxygen correlative to a disengagement of carbonic acid, is the act called respiratory in animals, and we can give it the same name in plants, forasmuch as the essential fact is identical in the two kingdoms. Animal and plant absorb aérian oxygen: animal and plant, while producing heat, water, and carbonic acid, burn their fat and amylaceous matters. We even find in the vegetal cells a substance analogous to the principal residuum of the combustion of the albuminoids in animals, urea: namely asparagine, immediate azotised and crystalloidal principle. The respiratory property is essential to life: it is indispensable even to the chlorophyllian cells, which become incapable of reducing the carbonic acid when they lack oxygen, and this is why they are asphyxiated in an atmosphere of pure carbonic acid. Every living element is athirst for oxygen, and to such a degree that sometimes certain organisms steal it even from stable chemical compounds. Vibrionians, studied by M. Pasteur, decompose the tartrate of lime and transform lactic acid into butyric acid to procure for themselves oxygen. It is besides by an analogous process that in most of the vertebrates the anatomical elements deoxydise the hematoglobuline of the haematia. In the plant oxygen combines in ‘totality with the carbon of the tissue : for in pure oxygen there is perfect equivalence. Modern researches the most exact. have shown that vegetal growth operates only through the aid of the absorption of oxygen by the tissues of plants, and that this absorption 2 Dutrochet, De l’Endosmose, p. 326. H 2 100 BIOLOGY. [Boox 11. is proportional to the growth. It is, for example, very consider- able in germination. Thus seeds and buds absorb, in evolution, many times their weight of oxygen. It is the same with flowers, Flowers, like all the parts not green of plants, manifestly absorb oxygen; but they absorb it in great quantity, and, a curious thing, in the monoical plants, the male flowers absorb more oxygen than the female flowers. A fact deserving of remark is, that in all the organic. vegetal combinations, oxygen is always in smaller proportion than would be needful for the complete combustion of their carbon and of their hydrogen, for their total transformation into water and into carbonic acid ; and the fact is wholly in accordance with the theory of respiration. It ig known well, that one of the constant effects of oxydation : is a certain production of heat, and that the oxydation of the tissues is the principal source of animal heat. Though less active, vegetal oxydation produces likewise perceptible calorific effects, especially in germination and florescence. Barley grains heaped up for the preparation of malt heat much. In the spadix of the aroide, at the time of fecundation, the excess of temperature above the exterior medium may amount to 10 or 12 degrees. The same fact is observed, but in a less degree, in the isolated flowers of the Cucurbita, Bignonia radicans, Victoria regia, and so on.} However, the respiratory oxydation, and the nutritive or assimilative movement which results therefrom, are not effected except within certain limits of température. The minimum is variable as the species varies. According to M. Boussingault? the leaves of the larch decompose carbonic acid at 0°, 5 to 2°,5; those of the grass of the meadows between 1°, 5 and 3°, 5. According to MM. Cloetz and Gratiolet, the carbonic assimilation commences above 6 degrees in the Vallisneria, between 10 and 15 degrees in the Potamogeton. This absorption of oxygen is by no means comparable with 1 J. Sachs, Tratté de Botanique, p. 847. * Boussingault, Comptes Rendus de V Acad. des Sciences, LXVIII. Cuap. I1.] VEGETAL NUTRITION. 191 that which is produced after the death of the plant, and which has for result the mineralisation more and more complete of the organised tissues, deprived of life. In the last case special chemical combinations are produced: first of all, a ternary compound, ulmine (C* H1¢ O14), which is transformed into a series of derived products more and more oxygenised (ulmic acid, humine, humic acids, and so on). Such of these products as are acid join themselves to the ammonia formed also during the cadaveric decomposition of the plant; they then constitute soluble salts, which can be reabsorbed by the roots, and thus be restored to the vital movement. To terminate this abridged description of vegetal respiration, it remains for us to indicate by what paths the air introduces itself into the mechanism of the vegetal tissues. In the inferior plants, the mosses and the conferve, there is no aérian circulation, no special apparatus. The oxygen is absorbed direct by the cells. In the complex plants, having true roots, true aérian leaves, canals, there is a commencement of functional specialisation. The air is absorbed a little by the bark, but especially by the leaves. Th. de Saussure, when analysing the interstitial air of plants, found that the air the least modified, the least poor in oxygen, is that of the leaves; that of the stems is less oxygenised, and that of the roots still less. The air probably penetrates into the phanerogamous plant by the stomata of the inferior surface of the leaves. Thus if we plunge leaves into water and if we subject them to the action of the pneumatic pump, we see the air escaping regularly in bubbles by the section of the vessels of the petiole (Dutrochet), Once intro- duced by the stomata, the air circulates in the lacunae, the inter- cellular meatus, especially in the trachee and the punctuated tubes, when the first flow of sap in spring has forsaken them. In the aquatic leaves destitute of epidermis and of stomata the aérian water acts direct on the cells, with thin walls, of the parenchyma. When there’are stomata the process is the same as in the open air. 102 BIOLOGY. [Book 11. In the complex plant, the air is therefore subjected to a sort of circulation, which Dutrochet justly compares with the aérian circulation in the trachee of insects which are likewise furnished with stomata. Once introduced into the vegetal tissues, the air is absorbed by the anatomical elements, and by the sap or the blastemas which it contributes to elaborate. Finally it is probable that a part of the oxygen resulting from the reduction of the carbonic acid by the green parts, and which is consequently in the nascent state, that is to say, eager to enter into new combinations, is also forthwith absorbed, or even mechanically driven into the canals and cellular interstices. 4, Sap Elaborated or Descendent. The water of the soil, more or less charged with the sub- stances in dissolution, penetrates by endosmosis into the cells of the spongioles, and thence is impelled into the vessels, the meatus, the anatomical elements, step by step. Finally it is in some sort inhaled by the whole of the tissues, which all have need of nourishment, and more specially by the leaves and the green parts. These chlorophyllian tissues are the special exhaling and assimilative organs, in the midst whereof the sap undergoes a very important elaboration, and in a fashion passes into the state of true blastema. So far in effect the sap was nothing more than a simple mineral solution. In the leaves the sap is vitalised, it becomes an organisable liquid. It is only after this metamorphosis of the sap that new anatomical elements can be formed at its expense, that the organism expands and grows. This sap thus modified has been called sap descendent, because its ‘ordinary course is from the leaves to the roots. It is interesting to follow the flow of this elaborated sap, to see how it passes and distributes itself from the leaves to the root of the plant. _ It is needful for us here to take anew into account the effect of the endosmosis, which plays moreover such a foremost part in Cuap. 11.J VEGETAL NUTRITION. 103 all the nutritive mechanism of the plant. Besides their special chlorophyllian function, and perhaps in consequence of that function, the leaves exercise on the sap a double propulsion : they aspire it from below to above, and they drive it back, after elaboration, from above to below. This is doubtless a kind of circulation, but rudimentary, without regularity, effected little by little, sometimes by one route, sometimes by another. The cells of the leaves, whose contents are dense and albuminoidal, are well arranged for absorbing by endosmosis the ascending lymphatic sap, to determine there, when it has penetrated into their cavity, synthetic chemical phenomena, to carbonise it, that is to say, to enrich it with atoms of carbon, thanks to their special property, then finally to expulse it by exosmosis. At the same time they concentrate it by depriving it of a notable portion of its aqueous vehicle, which is exosmosed, and escapes by evaporation. Experience has demonstrated that this exhalation is an active phenomenon, the result of a vital act, probably chlorophyllian, and not a passive evaporation, The confirmatory facts are numerous. Hales was the first to discover that light augments the aqueous exhalation on the surface of the leaves. The phenomenon depends on the solar light and very little on heat : for, simple light diffused, slightly calorific, suffices, whilst in the shade a heat equal or even very inferior does not act much, and at night the aqueous exhalation stops. If of two simple plants one is exposed to the light, and the other is kept in darkness, the first absorbs much more water than the second. Sennebier has shown that leafy boughs dipped in water at their lower extremity aspire much more water in light than in darkness. He observed also that heat in darkness has little influence on this sort of suction, and that the results vary according to the species of plants. In general the plants which in the light resist the most the desiccating action of the atmosphere are those which in darkness resist it the least, and. reciprocally. The intense contact of the air with the cells of 104 BIOLOGY. [Booz ur. the leaves is necessary to this aqueous aspiration, as the following fact’ proves. Dutrochet having plunged into water a leaved stalk of Pisum sativum, deprived it of its interstitial air by means of a pneumatic pump. The adrian cavities, once purged of air, were promptly invaded by water. The plant was then taken from the water and the extremity of its stalk was alone kept in it. It was, in this state, exposed to the diffused light, but it had become inca- pable of aspiring water, and was asphyxiated, or rather it was incapable of aqueous aspiration because it was asphyxiated. From the preceding facts it clearly results that the ascension of the sap is bound in a certain measure to the functionment of the leaves, and that this functionment, which comprehends simple aqueous exhalation, is subordinated, like every physiological act, to the absorption of oxygen by the anatomical elements, to respiration. We must note a fact, whose explanation is however easy, namely, that the absence of light has not on the green corolle the action which it exercises on the chlorophyllian leaves. As these corolle respire simply after the manner of the animal anatomical elements, by absorbing oxygen and without acting on the carbonic acid, the absence of light does not hinder them from living, from aspiring sap, and so on. Once elaborated and concentrated by the special action of the leaves, the sap comes forth from the cells by exosmosis, and just as the endosmotic action of the radical spongioles has driven the lymphatic sap from below to above, toward the branches and the buds, the exosmotic impulsion drives back the elaborated sap from above to below, from the leaves to the roots. We have seen that the ascension was especially accomplished through the ligneous centre, or at least through its yourigest, peripheric part ; the descent of the sap, on the contrary, is more habitually achieved through the bark. In ascending it enriches itself more and more, either carrying along with it the substances contained Cuap. 11] VEGETAL NUTRITION. 105 in the cells which it bathed in its passage, or by the special action of the green leaves ;+ in descending it is impoverished, on the contrary, more and more, for in going along, either it relinquishes organisable substances at the expense of which anatomical elements are formed, or it simply deposits in already prepared cavities masses of nutrimentary or organisable matters. We have just described, in a fashion, the schematic mode of the circulation of the sap ; doubtless there are numerous irregularities, and the sap undergoes in its course diverse impulsions, diverse deviations. The exosmotic impulsion is not the sole cause of the descendent propulsion. We must likewise take into account, as for the ascending sap, the relative void, made by the fixation of a duliquid part, by the nutrition and the formation of the tissues, and lastly, mechanical influences. For instance, it has been remarked that the agitation of the stems by the wind favours the growth of plants. Knight made on this subject precise experiments by immobilising certain stems. We are justified in thinking that the waving and the bending of the stems have as a result local pressions which aid the march of the sap in the canals. This descendent march of the elaborated sap must be slower than that of the aqueous sap; for this time we have before us a liquid, denser, more viscous, even sometimes differentiated. In effect there are assuredly diverse species of sap. for we must consider as such the milky liquid called Jatex, existing in great abundance in the cortical system of lettuce, of the fig-tree, of the euphorbie, and soon. The gum of trees of the Pinus kind, and so on, the resin of the conifers, are probably also sap residua. 1 Knight collected in the spring at various heights the sap of the sycamore and of the birch. These are the variations of specific weight which he observed on the sycamore :— Level of thesoil . . . . ~~ . 1,004 Atsevenfeet . ..... =. . 1,008 At twelvefeet . . .... =. =. 21,102 In the last case the sap had moreover a sugary savour. 106 BIOLOGY. [Boox 11. The sap can descend by the aubier or by the ligneous tissue of the central system. Knight having decorticated circularly a stem of Solanum tuberosum, saw the subterranean tubes developing them- selves indeed less, yet still developing themselves; in which case the sap could only have descended by the bark. The same observer has demonstrated that the elaborated sap can take an ascending ae when it is dissolved and carried on by the lymphatic sap.1 Furthermore the lymphatic sap can take a descendent movement, for example, when it forms in the leaves, absorbing the water which moistens them. When we cut the stem of a plant containing abundance of liquids, for example a milky plant, we see the latex flowing fromi the two surfaces of section There is here a simple sap movement, determined by the elastic pression of the canals primitively distended, turgid through the action of the endosmosis. In sum, the sap, elaborated or not, passes where it can. A root which had become naked Dutrochet cut, during winter, lower down than a shoot which it nad produced ; he saw, the following spring, this shoot continue to live. The development of the leaves had not yet taken place ; consequently the shoot lived without elaborated sap, by the mere help of the lymphatic sap, driven now from above to below. Knight having cut off from a forward variety of Solanum tuberosum the runners which produce the tubers, there resulted in the stem a plethora ofelaborated sap. The plant, which usually is not florescent, had flowers, fruits, and even small tubers were developed on many of the aérian parts of the plant. If in the spring we cut a vine-root we see the lymphatic sap flowing from the superior or central trongon as from an aérial stem. Dutrochet observed that the trunk of a tree cut down during winter and completely stripped of its branches presents never- theless in spring an outflow of elaborated sap under its bark. This sap existed therefore in the central part of the vegetal 1 Knight, Philosophical Transactions, 1805, Crap, I1.} VEGETAL NUTRITION. 107 tissue, forasmuch as it came neither from the leaves nor from the roots. It had been already prepared, and must have reached the periphery by means of the transversal medullary radii. It is probably because the monocotyledonous plants have none of these transversal medullary radii that there is not in them any flow of sap between the cortical system and the central system, and consequently no growth at the point of junction of these two systems.! In sum, there is no true -circulation of sap, forasmuch as the course of the nourishing liquid is at the mercy of a number of accidents. There are only two principal sources of the sap: the spongioles of the roots, which introduce into the plant the aqueous or lymphatic sap, and the leaves, which elaborate this sap already thickened and enriched, to impel it afterwards to the lower part of the plant, by all the paths that are practicable. 5. Algae and Mushrooms. We have just presented a rapid picture, or rather given the enumeration, of the different phases of nutrition in a complex plant having roots, stems, and leaves. Naturally things come to pass otherwise in the inferior plants, composed almost wholly of cellular tissues, in what are called in these days Thallophytes, in the alge and mushrooms. Here there are neither true vessels nor true roots. The aliments are absorbed by the cells which are in contact with them, and transmitted by endosmosis from point to point. Nevertheless the alge have still fellowship with the higher plants by the presence of chlorophyll, even in the coloured alge, where it is masked by colouring matters (nostochinee, and so on). Chlorophyll acts there as it acts everywhere; it absorbs and assimilates carbon, and only operates in the light. In many thallophytes the elementary cell has taken the 1 Dutrochet, De ’ Endosmose, p. 387. 108 BIOLOGY. [Boox 11. elongated form of a filament, simple in certain intermediary alge (phycomyceta), divided transversely by partitions in others, and sometimes ramified (mucedinez). The nutritive characteristic of the mushrooms is the absence of chlorophyll. Through this characteristic the mushrooms resemble the animal organisms. They are incapable of assimilating direct the aérian carbon, and have no need of light. We can even see some of them living under the soil, as for instance the truffles, and soon. From the absence of chlorophyll it also results that the mushrooms, like animals, have need of aliments wholly prepared, of combinations carbonised, assimilated by other organs. Thus when they are not parasites they have to live at the expense of organic matters in process of decomposition. Furthermore, and this is a general characteristic, they are incapable of forming a single granule of starch. This fact explains in a certain measure the office of chlorophyll in the synthetic chemistry of the vegetal organism, and serves us as transition to pass to the following chapter. CHAPTER III. VEGETAL ASSIMILATION AND DISASSIMILATION. 1. Organic Substances. Berore speaking of the chemical transformations of which the vegetal organism is the seat and the agent, it will not be useless to enumerate the various bodies which penetrate into the living plant from the ambient medium. j We have seen the'roots, and sometimes the leaves, absorb water, of which the plant has an imperious need. We know that the water absorbed by the roots is loaded with substances in solution. Among these substances, some are terreous, and we shall pass them under review at a future time in this exposition (salts of lime, soda, potash, ammonia, &c.). It is through the roots that the larger part of the azote which is necessary to the plant penetrates into it. This azote is introduced into the plant in the form of salts of ammonia and especially of a series of substances produced from the slow oxydation of the organic detritus. The type of these substances is a compound of ©, H's, O", ulmine, which, according to Miilder, is transformed by a gradual sur-oxygenation into ulmic acid, humine, humic and geic acids, &c. The acids of this series eagerly absorb ammonia, and compose with it soluble salts, They form also soluble alkaline salts, and terreous salts, which would be insoluble if the ammonia did not form therein an aggregation of double salts. Aecording to Miilder, water co-operates with these formations, 110 BIOLOGY. [Book 1 being decomposed to oxydize these matters, and a part of it: hydrogen combines itself with the azote of the air and form: ammonia, Plants raised in ulmic acid and powdered charcoal, entirely deprived of ammonia, shut up in an atmosphere and watered with water which was also destitute of it, have yielded to analysis a double or treble quantity of azote to that which their seed contained at the commencement of the experiment. In this case, the plant being deprived of ammonia, it is very possible that it had absorbed the azote directly from the air. The following facts render this a very probable eventuality :— Schroeder sowed cereals in flower of sulphur watered with distilled water, and contained in vessels of glass or porcelain covered with a receiver. The seeds germinated, and produced halms from 2 to 14 inches in length, bearing short ears, which however flowered. When dried, they were five times the weight of those seeds from which they sprang. Boussingault sowed twenty-nine seeds of clover in sand previously reddened in the fire. The plants which they produced weighed 67 grains at the end of three months. (Annales de Chimie, t. xxvii.) Peas treated in the same way yielded in the same space of time plants weighing 72 grains, loaded with flowers and perfect seeds, &c. (Quoted. by Burdach, Traité de Physiologie, t. ix. p. 255.) Finally, as we shall see further on, recent experiments of M. G. Ville put the normal absorption of atmospheric azote by the plant almost beyond doubt. If the anatomical elemerits of plants bring about many chemical syntheses, they are also very capable of disaggregating mineral compounds. We know that chlorophyll decomposes the carbonic acid of the air. It has been also observed, that seeds germinating in water decompose it, and absorb a portion of its hydrogen. The oxygen contained in a plant comes in a large degree from the aérian medium ; a notable portion of it from the decomposi- tion of the carbonic acid by chlorophyll. The plant also Cua. 111.] VEGETAL ASSIMILATION AND DISASSIMILATION. 111 procures it in another way. In general, as we have seen, the nutritive substances absorbed by the roots are very rich oxygenised compounds ; on the contrary, the assimilated substances, forming a large portion of the dry matter of ‘plants, are either poor in oxygen, or do not contain it at all. Assimilation must then be specially an act of dis-oxygenation ; now we know that it takes place particularly in the chlorophyllian cell. We have then here, as Sachs justly remarks, the place, the conditions, and the time of this dis-oxygenation.! In fact, it is in the chlorophyllian cells that assimilation, or rather the vitalization, of various substances introduced into the plant takes place. It is towards this living and active laboratory that they converge ; it is there that they enter into conflict with .. each other. The chlorophyllian cell is a powerful apparatus of synthesis, effecting organic combinations which still defy the power of contemporary chemistry. The molecules of azote, carbon, oxygen, hydrogen, &c., penetrate the cellular cavity, some free, others entangled in combinations more or less complex. There they are mixed together, dragged into the circular current of the cellular protoplasm, subject to the attraction exercised upon them by the chlorophyll, and, on the other hand, shaken by the undulations of the yellow rays of solar light which add their impulsion to the vibrations by which they are already animated. The atoms and the molecules yield to these united influences ; those partiéles which are involved in combinations abandon them, resume their liberty, and all unite to form living organic substances, ternary and quaternary substances. We have already said a few words upon the advent and aspect of one of these substances, one of the most important in vegetal physiology, starch. Starch is especially formed in the green cells, and even in the interior of the chlorophyllian bodies. We have seen that its formation is in direct dependence upon the chemical operation of the ‘chlorophyll, consequently upon light. It 1 J. Sachs, Joc, cit., p. 821. 4 112 BIOLOGY. [Book rr. appears under the influence of light, and in its absence re- dissolves. We seize here chemical synthesis in some degree in the very act. Assuredly proteic substances are also formed in the chlorophyl- lian cell. Doubtless the phenomenon is less evident here ; but we know that the sap reaches the leaves in the state of a fluid still very slightly charged, and that it issues from them as a living liquid in the state of nutriment and blastema. We have just said that chemical synthesis, exercised upon the chlorophyllian cell, had probably resulted in’ a subtraction, an emission of oxygen; but there are, on the contrary, organic compounds that result from super-oxydation; these are the vegetal acids, Their molecule contains more oxygen and hydrogen than are required to form water. Oxalic acid, one of the most, frequent, contains three atoms of oxygen to two of carbon (C0). In laboratories, it is obtained by oxydizing sugar and fecula with azotic acid. In the plant, it is probably produced by the direct action of oxygen upon the same substances. Oxalic acid, in fact, as well as the ternary, acetic, citric, and malic acids, and so on, is not formed in the synthetic laboratory of the chlorophyllian cells, but in those parts which are not green, or which are sheltered from the light Organic vegetal substances are naturally subject in a high degree to isomerism and instability, like all aggregates of this kind ; they also often undergo metamorphoses during the course of the nutritive process. Their molecular mutations succeed and engender each other, The spores, seeds, bulbs, tubers, rhizomas, the vivacious shoots of ligneous plants are in truth nutritive reservoirs, where the organised sap deposits organic substances, utilizable at a later time, either for germination or for nutrition, when the flow of lymphatic sap reappears in spring. These substances are then drawn away, and furnish materials for the development of the folial and floral buds, for the nutrition of the tissues, which could not otherwise obtain aliment, frondation not yet existing ; but ° Cuap. 01.) VEGETAL ASSIMILATION AND DIS-ASSIMILATION. 113 before being drawn away and utilized, these substances in reserve often undergo metamorphoses. The fecula, deposited in autumn in the ligneous body of the trees, is often in spring transformed into sugar, which, in certain plants, the maple, for example, mixes largely with the ascending sap. MM. Payen and Persoz have shown that there is first of all produced a matter called by them diastasis. This matter has the property of rendering the fecula soluble, by transforming it first into dextrine, then into sugar. It produces this isomeric transformation by means of very small quantities, for it is capable of rendering soluble five thousand times its own weight of fecula. As to the albuminoidal substances in reserve in expectation of the spring sap, such as starch, sugar, inuline, and fat, certain among them, not having lost any of their solubility, are simply seized anew, drawn away, and finally assimilated. Others also undergo their isomeric modifications, specially in germination. Thus, during the germination of the leguminous plants, caseine is metamorphosed into albumine in the cotyledons. In the gramineous plants, the gluten of the endosperm, which is insoluble in water, is dissolved during germination, and is conveyed into the plantule. The energetic oxydation which always accompanies germination also determines the formation of regressive sub- stances, for example, asparagin, which is perhaps re-assimilated at a later period. A certain portion of carbonated hydrates is also totally burned, converted into water and carbonic acid by vital oxydation. In this case, the hydrates are burned either in the anatomical elements, or in the sap of the plant, as they are in the blood of the animal, proving once more that there is no antagonism between the vegetal kingdom and the animal kingdom, and that essentially the primordial phenomena of life are identical in the two kingdoms. As Cl. Bernard has very well observed, if an animal eats the sugar accumulated in beet-root, that does not prove that this sugar was made for him. On the contrary, it was destined (if I 14 BIOLOGY. [Boox 11. ve may employ this word in speaking of blind organic finality) —it was destined to be burned by the beet-root itself during the econd year of vegetation, when florescence and fructification are leveloping themselves. However this may be, the nutritive substances, when suf- iciently elaborated, are assimilated ; that is to say, their molecules ntercalate themselves between the organic molecules already ormed, either to replace those which have been destroyed, or to ing about the enlargement. of the cell; others spontaneously rganize themselves in the blastemas. We may form some probable conjectures as to the special office f the various categories of organic substances. It is probable hat the hydrates of carbon and the fatty bodies are especially ransformed into cellular membranes, these membranes being prin- ipally constituted of cellulose, the molecule of which is almost adentical with that of starches, sugars, and fats. Thence come lso without doubt the vegetal acids, tannin, and the colouring iatters. The proteic substances are probably employed in the formation f internal azotized utricles included in the cells, and of the ellular protoplasm and the chlorophyllian particles. They also furnish, but by incomplete oxydation, by degradation, sparagin, of which we have spoken, and without doubt the egetal alkaloids (quinine, morphine, strychnine, &c.), quaternary ut not proteic substances, and of which the molecule, very omplex, very rich in carbon, and tolerably rich in hydrogen, ontains also a notable proportion of oxygen and very little zote. i 2. Inorgante Substances. Besides atmospheric gases, a number of mineral substances are otroduced into the plant through the roots. The principal’ are lkaline and terreous bases: potash, soda, ammonia, magnesia, ime, generally salified by sulphuric, azotic, phosphoric, silicious nd carbonic acids. Many of these substances do not contribute Cuap. 111.] VEGETAL ASSIMILATION AND DIS-ASSIMILATION. 115 anything to the nutrition of plants ; they are mechanically driven by the water which penetrates into the plant, and are deposited in the deep tissues, after having formed insoluble salts with the vegetal acids. 7 Habitually, these mineral particles are uniformly intercalated between the organic molecules; also by incineration, or by treating the vegetal anatomical elements with certain acids, we may succeed in destroying the organic substances which they contain, preserving only the mineral skeleton, but nevertheless keeping the form of the destroyed anatomical element. Often the mineral salts also form true crystals in the vegetal tissues and even in the cells. Such, for example, are fine granulous incrustations of carbonate of lime, bundles of spars of oxalate of lime, or even tolerably voluminous crystals. The amount of mineral matters in a plant is proportioned to its age, and also to the quantity of water which flows through it ; in short, to the activity of the vegetation. The proportion of soluble substances may undergo certain variations. As to the insoluble substances, they accumulate ceaselessly, mineralizing the plant more and more, and contracting the range of action of life. If most of the mineral substances drawn from the soil are of little use in the development and nutrition of plants, yet some of them are very important, for example, ammonia, the phosphates and the sulphates. Others again appear sometimes necessary to one plant or group of plants, sometimes to another. Most plants which grow on the sea-shore contain much soda, and this soda is necessary to them; for they grow only upon the sea-coast or near saline deposits inland. We always find in the tissues of plants of certain very natural families, the same mineral substances. They have thus chosen them in a certain degree. We may mention the gramineous plants, the stems of which, without exception, contain silica, whilst the fruits contain phosphate of magnesia and of ammonia. But often the same plants contain different salts, according as they grow in various. soils. 12 116 BIOLOGY. [Boox 1. Let us notice, however, that it is possible, under the condi- tions of artificial culture, to rear, without silica, plants which habitually contain much of it, maize for example. Lime seems to be indirectly useful to plants, by serving as a vehicle to the sulphuric and phosphoric acids, and by neutralizing the oxalic acid, hurtful to the plant in which it is formed ; but any other base could do as much. 3. Influences of Light, Heat and Electricity. i We have already spoken at length upon the influence of solar light upon vegetal nutrition. It is such, that, without this influence, nearly the whole of the’ vegetal world would cease to exist. In consequence, the animal kingdom, which, in the continental parts of the globe, lives, directly or not, at the expense of the vegetal kingdom, would also become extinct, at least in its higher branches, on the surface of these terrestrial regions. In effect, without solar light, mushrooms alone, of all plants, could still live upon the continents. But animal life would probably find refuge in the sea. A number of the lower marine animals are nourished and live without the help of plants. Now these rudimentary organisms, to which we must grant the faculty of synthetising complex organic substances, after the manner of plants, could themselves furnish alimentation for higher aquatic animals, as often actually happens. All this aquatic fauna can thus live without light. This is even the case now, as the dredgings and soundings made, during the last few years, at the bottom of the ocean and of large lakes has proved. Solar light only penetrates the sea to a very small depth.” Below 50 fathoms (1 fathom =: 1™ -82,) a very sensitive photo- graphic paper is no longer impressed. At this depth also, the vegetal kingdom is only represented by rare specimens, and below 200 fathoms it absolutely disappears. Now the bottom of the Atlantic ocean, which is as much as 1400 and 1500 metres Cap. 111.] VEGETAL ASSIMILATION AND DIS-ASSIMILATION, 117 deep, is covered with organized beings, all belonging to the group of the Protozoa of Heckel. This bottom is everywhere car- peted with those little sarcodic, gelatinous, contractile organ- isms, called by Huxley Bathybius Hackelit. Amongst these bathybians live foraminifers, rhizopods, radiolites, sponges. We therefore must admit that certain of these rudimentary animal organisms can decompose water, carbonic acid, and ammonia, or assimilate the numerous. organic detritus in suspen- sion in the marine waters, arising from the dejections of animals, and from the decomposition of their dead bodies. It is only thus that they can live, can multiply, and can aliment more complex animals. Analogous facts have been observed by MM. de Candolle, Forel, and Dufour, in the Lake of Geneva. There also the most sensitive photographic paper ceases to take an impression beyond the small depth of 50 or 60 metres in summer, and 40 or 50 in winter. Nevertheless, at the bottom of the lake live from thirty-five to forty species of lower animals. The idea of a necessary solidarity between the two organic kingdoms must then be abandoned. This solidarity only exists, in a very large measure, in the organized terrestrial world. There, we may admit, as a general thesis, that the vegetal kingdom is necessary to the animal kingdom. Now nearly the whole of plants cannot live without light. But the calorific and chemical solar rays are not less necessary to the maintenance of life. Solar irradiation is then one of the grand causes of the production, development, and duration of organized beings. The great theory of the transmutation and correlation of physical forces is therefore applicable to biology. We must guard, however, against making this application with a mathematical and inflexible rigour which the subject does not allow of. We think also that there has been too great an inclination of late years to consider solar irradiation as the unique and universal 1 The Depths of the Sea, by C. Wyville Thomson. 8vo. London, 1873. French Translation ; Les Abimes de la Mer, 8vo. Paris, 1875. 118 BIOLOGY. [Boox 11. cause of life upon the surface of the globe. With these reser- vations, we cannot deny that solar irradiation is fixed, accumulates in the plant, and that, in the infinitely numerous cases in which the plant serves as animal alimentation, this irradiation is treasured up by it, transforms itself into various series of ‘molecular vibrations, into heat, movement,. thought, etc. We have not to return here to the chief office fulfilled by light in the nutrition of plants; but, besides the phenomena of synthetic chemistry accomplished by chlorophyll, light also produces in plants certain secondary phenomena, which probably depend upon the chlorophyllian property. Thus many plants sleep in the night, that is to say, droop their leaves or follicles more or less, or rather gather them up along the stem or principal petiole. This phenomenon assuredly depends upon the light, since De Candolle was able to make sensitive plants sleep in the day in artificial darkness, and, on the other hand, succeeded in waking them at night by the light of lamps.! This so-called slumber, this sinking down of the leaves, arises probably from a diminution of the turgescence of the tissues, and this diminution is assuredly the result of the inaction of the chlorophyllian cells, which, no longer exhaling, no longer forming organic syntheses, summon less water into the petiolary canals, the meatus, and so on. If the luminous undulations are, as it were, the soul of vegetal life, caloric undulations are not less indispensable to the nutrition of plants. Above and below a certain temperature, vegetal life veases. Speaking generally, the thermometric limits of vegetal life are 0 degree and 50 degrees.2 It must be noticed that the cellular juices, being liquids very full of substances in solution, do not congeal at 0 degree. M. Uloth has seen seeds of Acer platanoides and triticum germinate between the fragments of ice 1 Mémoire sur VInfluence de la Lumiere artificielle sur les Plantes (Mém, des Savants Etrangers de V Institut, t. i.) 2 Sachs, Ueber die obere Temperaturgrenze der Vegetation (Flora, 1864). Cuar. 11,] VEGETAL ASSIMILATION AND DIS-ASSIMILATION. 119 in a glacier, and send down numerous roots, several inches in length, into ice destitute of crevices.! It is then probable that germination can still take place at 0 degree, and, as it always develops a remarkable quantity of heat, the result must have been, in the case mentioned by M. Uloth, the partial fusion of the ice, whence it became possible for the roots to penetrate. We have given the limits of temperature, but these vary according to species. Most plants succumb after remaining for ten minutes in water at from 45 to 46 degrees. In the air, phanerogams are killed after remaining from ten to thirty minutes in a temperature of from 50 to 51 degrees. To produce a lasting alteration, it is sometimes necessary that the tempe- rature should reach 60 degrees. Death then takes place through the coagulation of the albuminoidal substances. Dried vegetal tissues (seeds) can naturally support more extreme temperatures of heat or cold. Thus, tissues full of sap are killed at 50 degrees, whilst dried seeds of Pisum sativum may be heated with impunity to 70 degrees for an hour. In every plant each function has its special limits of tempe- rature. We cannot enter here into the enumeration of facts in detail. Moreover, we have already stated the temperatures necessary for the operation of chlorophyll. In cells killed either by congelation or by too high a tempe- rature, the cellular membranes become permeable ; liquids filter through : consequently turgescence ceases. First of all, the pro- toplasm becomes immovable, takes a sombre tint, and rapidly loses its water by passive evaporation. : Life is not sufficiently active in plants for them to have, like the higher animals, a temperature of their own, independent in some degree of that of the exterior medium, The small aquatic plants, and the subterraneous parts of terrestrial plants, have generally the temperature‘of the ambient medium. ‘On account of their volume, the massive stems follow more slowly the 1 Uloth, Flora, 1871. 120: BIOLOGY. [Boox 11. exterior thermometric variations, and consequently, they may be hotter or colder than the exterior medium. Electricity seems to exercise very little influence upon the nutritive movement of plants. Feeble constant currents, small sparks of induction, have no apparent effect either upon the movement of the protoplasm, or upon that of the mobile leaves. A too powerful current, a spark too strong, causes either the arrest of the protoplasm or that of the tissue. Thirty Grove elements instantly stop the protoplasmic movement. As to the electric state of the tissues, it is curious to observe in the plants phenomena very analogous to those which have been observed in the nerves and muscular fibres of animals, and have served as a basis for ‘many theories. In effect, in a cut stem, there is a current from the surface of the stem to the centre of section.1_ The electric currents, which, without doubt, result from the chemical assimilative and dis-assimilative reac- tions of nutrition, are not peculiar to such and such a vegetal or animal tissue. There again the two organic kingdoms touch and intermingle, 1 Buff, Annal. der Chimie und Pharmacie, 1854, Band 89. Jiirgensen, Stu- dien des Physiologisches Instituts zw Breslau, 1861, Heft I.—Heidenhain,