The principles of biology
Spencer, Herbert, 1820-1903
S SS SS SW AS \ \\ \\ Wo << \ WS \ \ WN \ \ A SN SW SS BARN SOS A CDECRP ) SSS MK WN \\\ WY WN \ . \ S \ A RQ MO S NS AX WY QQ Z, thi TLQQy \\ \ SS ~S SS SS S. WS IG << QQ Qo SN \ MG WRAY W WH MG SS = S Sh SSA qw° ~~ \\ \ SS XS ‘jv. \ SS WOQy. QQ Ry SSS NS DIVISION OF PHYSICAL ANTHROPOLOGY U. S$. NATIONAL MUSEUM THE HRDLICKA LIBRARY Dr. Ales Hrdlicka was placed in charge of the Division of Physical Anthropology when it was first established in 1903. He retired in 1942. During this time he assembled one of the largest collections of human skeletons in existence and made outstanding contributions to his science. On his death, September 5, 1943, he bequeathed his library to the Division, with te-prevision-that— it be kept exclusively in the said Division, where-it-may be consulted but not loaned out. Ae? Mitt ad tan’ Uy | y = whi, Hrakrirz q A SYSTEM OF SYNTHETIC PHILOSOPHY. VOL. II. Spencer's Synthetic Philosophy. FIRST PRINCIPLES . . ° I. Tot UNKNOWABLE. Il. Laws or THE KNOWABLE. THE PRINCIPLES OF BIOLOGY. Vol.I.. I. Tor Data or Broioey. Il. Tue Inpuctions or BIoLoGcy. III. Tue Evouution or Lire. THE PRINCIPLES OF BIOLOGY. Vol. II. IV. MorrPHoLogicaAL DEVELOPMENT. VY. PHystoLtocicaAL DEVELOPMENT, VI. Laws or MOLTIPLICATION. THE PRINCIPLES OF PSYCHOLOGY. VYol.I.. I. Tot Data or PsycHoLoey. II. Tae InpucTIons or PsycHoLoGy, Ill. GeneraL SYNTHESIS. IV. Specran SyNTHESIS. V. PuysicaL SYNTHESIS. THE PRINCIPLES OF PSYCHOLOGY. Vol. II. VI. Spectan ANALYSIS. VII. GENERAL ANALYSIS. VIII. CoroLuaries. PRINCIPLES OF SOCIOLOGY. Vol. I.. I. THE DATA OF SoctoLoey. Il. Tur InpuctTiIons or SOCIOLOGY. Ill. Tur Domestic RELATIONS. (7.) PRINCIPLES OF SOCIOLOGY. Vol. Il. I. CEREMONIAL INSTITUTIONS * * * # (8.) PRINCIPLES OF SOCIOLOGY. Vol. III. * * * * (9.) PRINCIPLES OF MORALITY. VYol.I.. I. Tue Dara or Eruics. . i i * * * * (10.) PRINCIPLES OF MORALITY. Vol. II. cS eee Es es D. APPLETON & CO., Pusiisners, New York. S745 THE PRINCIPLES 1) 5° / a | OY CL BIOLOGY, BY HERBERT SPENCER, AUTHOR OF “THE PRINCIPLES OF PSYCHOLOGY,” “ILLUSTRATIONS OF PROGR533,” ‘CESSAYS: MORAL, POLITICAL, AND ESTHETIC,” ‘‘ FIRST PRINCIPLES,” ““SOCIAL STATICS,’ “EDUCATION,” ETC. VOL. IN ES We NG OMCs = Pra kee Lhy TON, AN Dy. C OW P ANp Ye {3 AND. OB OND Stk Ber D if Suse. Entcred, according to Act of Congress, in the year 1566, By D. APPLETON & CO., In the Olerk’s Office of the District Court of the United States for the Southern District of New York. PREFACE TO THE AMERICAN EDITION. Tus System of Philosophy now in course of publication by Mr. Hersert SPENCER begins with a volume of First Princi- ples, which was republished in this country a year or two since. The subject of Biology comes next in order, and is to be treated in two volumes, of which the present is the first; Volume II. will probably appear toward the close of the year. In accordance with the author’s plan, the doctrine or method of Evolution unfolded in First Principles and applied to Biol- ogy in the present work, will be carried out in the subsequent treatment of the Principles of Psychology and the Principles of Sociology’. In the preface to the English edition, Mr. Spencer remarks: “The aim of this work is to set forth the general truths of Biology, as illustrative of, and as interpreted by, the laws of Evolution: the special truths being introduced only so far as is needful for elucidation of the general truths. “For aid in executing it, 1 owe many thanks to Prof Hux- ley and Dr. Hooker. They have supplied me with information where my own was deficient; and in looking through the proofsheets, have pointed out errors of detail into which I had fallen. By having kindly rendered me this valuable assist- ance, they must not, however, be held committed to any of the enunciated doctrines that are not among the recognized truths of Biology.” New Your, March, 1866. CONTENTS OF VOL. I. PART I.—THE DATA OF BIOLOGY. CHAP. PAga I.—ORGANIC MATTER Bigs oe ae ae 3 Il.— THE ACTIONS OF FORCES ON ORGANIC MATTER .. 28 1l1I.—THE RE-ACTIONS OF ORGANIC MATTER ON FORCES 42 IV.—PROXIMATE DEFINITION OF LIFE Ae pairs oS) V.—THE CORRESPONDENCE BETWEEN LIFE AND ITS CIR- CUMSTANCES hs es ais 2 ie VI.—THE DEGREE OF LIFE VARIES AS THE DEGREE OF CORRESPONDENCE Ne ate. AP 82 VII.—-THE SCOPE OF BIOLOGY me hi re= 2 94 PART II.—THE INDUCTIONS OF BIOLOGY. I.—-GROWTH is ff Bs ie hes ve TOR TI.— DEVELOPMENT BAS Ree we Samide IlI.—FUNCTION ae see ae cae Pa cme! 133 IV.—WASTE AND REPAIR ..¢ oe she me ase V.—ADAPTATION .. ae 98 ae Susy Vii CONTENTS. CHAP. VI.—INDIVIDUALITY a ee oe oe VII.—GENESIS oe oe oe os se VIIIL—HEREDITY .. : ee oe ae {X.—VARIATION .. oe ee ae ts X.—GENESIS, HEREDITY, AND VARIATION .. oe XI.—CLASSIFIOATION 54 56 ie = XII.— DISTRIBUTION 55 5 Bite sc PART TJI.—THE EVOLUTION OF LIFE. I.— PRELIMINARY a 55 we Ab Il.— GENERAL ASPECTS OF THE SPECIAL-CREATION-HY- POTHESSS °° se ae oan III.— GENERAL ASPECTS OF THE EVOLUTIUN-HYPOTHESIS IV.—THE ARGUMENTS FROM CLASSIFICATION oe V.—THE ARGUMENTS FROM EMBRYOLOGY ete °. VI.— THE ARGUMENTS FROM MORPHOLOUY Sale ite VII. THE ARGUMENTS FROM DI8TRIBUTION .. ee VIII.—HOW IS ORGANIC EVOLUTION CAUSED? .. ue IX.—EXTERNAL FACTORS .. oP ae ots X.—INTERNAL FACTORS. .. fe ie a XI.—DIRECT EQUILIBEATION ae a ae XII.— INDIRECT EQUILIBRATION ie - Re XIII.— THE CO-OPERATION OF THE FACTORS .. ae XIV.—THE CONVERGENCE OF THE EVIDENCES .. ee PAgga 201 209 239 257 273 292 31] PARTI. THE DATA OF BIOLOGY CHAPTER 1. : ORGANIC MATYER. @ 1. Or the four chief elements which, in various com- binations, make up living bodies, three are gaseous. While carbon is known only as a solid, oxygen, hydrogen, and nitrogen are known only in the aeriform state. Under pressures great enough to reduce them almost to the density of liquids these elements have still defied all efforts to liquefy them. There is a certain significance in this. When we remember how those re-distributions of Matter and Motion which constitute Hvolution, structural and functional, imply motions in the units that are re-distributed ; we shall see a probable meaning in the fact that organic bodies, which exhibit the phenomena of Evolution in so high a degree, are mainly composed of ultimate units having extreme mobility. The properties of substances, though destroyed to sense by combination, are not destroyed in reality : it follows from the persistence of force, that the properties of a compound are resultants of the properties of its components—resuléants in which the properties of the components are severally in full action, though greatly obscured by each other. One of the leading properties of each substance is its degree of molecular movility; and its degree of molecular mobility more or less sensibly affects the molecular mobilities of the various compounds into which it enters. Hence we may infer some relation between the gaseous form of three out of the four 4 THE DATA OF BIOLOGY. chief organic elements, and that comparative readiness dis- played by organic matters to undergo those changes in the arrangement of parts which we call development, and those transformations of motion which we call function. Considering them chemically instead of physically, it is to be remarked that three out of these four main components of organic matter, have affinities which are narrow in their range and low in their intensity. Hydrogen combines with comparatively few other elements ; and such chemical energy as it does show, is scarcely at all shown within the limits of the organic temperatures. Of carbon it may similarly be said that it is totally inert at ordinary heats; that the number of substances with which it unites is not great; and that in most cases its tendency to unite with them is but feeble. Lastly, this chemical indifference is shown in the highest degree by nitrogen—an element which, as we shall here- after see, plays the leading part in organic changes. Among the organic elements, including under the title not only the four chief ones, but also the less conspicuous re- mainder, that capability of assuming different states, called allotropism, is frequent. Carbon presents itself in the three unlike conditions of diamond, graphite, and charcoal. Under certain circumstances, oxygen takes on the form in which it is called ozone. Sulphur and phosphorus (both, in small proportions, essential constituents of organic matter) have allotropic modifications. Silicon, too, is allotropic; while its oxide, silica, which is an indispensable constituent of many lower organisms, exhibits the analogue of allotropism —isomerism. And even of the iron which plays an active part in higher organisms, and a passive part in some lower ones, it may be said that though not known to be itself allo- tropic, yet isomerism characterizes those compounds of it that are found in living bodies. Allotropism being interpretable as some change of molecular arrangement, this frequency of its occurrence among the components of organic matter, is significant as implying a further kind of molecular mobility. ORGANIC MATTER. 5 One more fact, that is here of great interest for us, must be set down. These four elements of which organisms are almost wholly composed, present us with certain extreme antitheses. While between two of them we have an unsur- passed contrast in chemical activity ; between one of them and the other three, we have an unsurpassed contrast in molecular mobility. While carbon, by successfully resisting fusion and volatilization at the highest temperatures that can be produced, shows us a degree of atomic cohesion greater than that of any other known element, hydrogen, oxygen, and nitrogen, show the least atomic cohesion of all elements. And while oxygen displays, alike in the range and intensity of its affinities, a chemical energy exceeding that of any other substance (unless fluorine be considered an exception), nitrogen displays the greatest chemical inactivity. Now on caling to mind one cf the general truths arrived at when analyzing the process of Evolution, the probable significance or this double difference willbe seen. It wasshown (frst Principles, § 123) that, other things equal, unlike units are more easily separated by incident forees than like units are—that an inci- dent force falling on units that are but little dissimilar does not readily segregate them; but that it readily segregates them if they are widely dissimilar. Thus, these two extreme contrasts, the one between physical mobilities, and the other between chemical activities, fulfil, m the highest degree, a certain further condition to facility of differentiation and in- tegration. § 2 Among the binary combinations of these four chief organic elements, we find a molecular mobility much less than that of these elements themselves; at the same time that it is much greater than that of binary compounds in general. Of the two products formed by the union of oxygen with carbon, the first, called carbonic oxide, which contains one atom of carbon to one of oxygen (expressed by the symbol C Q), is an incondensible gas; and the second ra THE DATA OF BIOLOGY. carbonic acid, containing an additional atom of oxygen (C O,) assumes a liquid form only under a pressure of nearly forty atmospheres. The several compounds of oxygen with nitrogen, present us with an instructive gradation. Protoxide of nitrogen, which contains one atom of each element (N QO), is a gas condensible only under a pressure of some fifty at- mospheres; deutoxide of nitrogen (N O,) is a gas hitherto uncondensed (the molecular mobility remaiming undiminished in consequence of the volume of the united gases remaining unchanged) ; nitrous acid (N Q,) is gaseous at ordinary temperatures, but condenses into a very volatile liquid at the zero of Fahrenheit ; peroxide of nitrogen (N O,) is gaseous at 71°, liquid between that and 16°, and becomes solid at a tem- perature below this ; while nitric acid (N O,) may be obtained in crystals which melt at 85° and boil at 113°. In this series we see, though not with complete uniformity, a de- crease of molecular mobility as the weights of the compound molecules are increased. The hydro-carbons illus- trate the same general truth still better. One series of them will suffice. Marsh gas (C, H,) is permanently gaseous. Olefiant gas (C, H,) may be liquefied by pressure. Oil gas, which is identical with olefiant gas in the proportions of its constituents but has double the atomic weight, (C, H,), becomes liquid without pressure at the zero of Fahrenheit. Amylene (C,,H,,) is a liquid which boils to 102°. And the suc- cessively higher multiples, caproylene (C,, H,,), caprylene (C,, H,,), elaene(C,, H,,)and paramylene (C,) H.), are liquids which boil respectively at 102°, 131°, 257°, 230°, and 329°, Cetylene (C;. H,,) is a liquid which boils at 527°; while pa- rafline (C,, H,,) and mylene (C,) H,,) are solids. Ont one compound of hydrogen with nitrogen has been obtained in a free state—ammonia (H, N); and this, which is gaseous, is liquefiable by pressure, or by reducing its temperature to —40° F. In cyanogen, which is composed of nitro- gen and carbon (N C,), we have a gas that becomes liquid at a pressure of four atmospheres and solid at —30° F. And, in ORGANIC MATTER. rf paracyanogen, formed of the same proportions of these ele- ments in higher multiples (N; C,), we have a solid which does not fuse or volatilize at ordinary temperatures. Lastly, in the most important member of this group, water, (H O or else as many chemists now think H, O,) we have a com- pound of two incondensible gases which assumes both the fluid state and the solid state within ordinary ranges of temperature; while its molecular mob'lity is still such that its fluid or solid masses are continually passing into the form of vapour, though not with great rapidity until the temper- ature is raised to 212°.* | Considering them chemically, it is to be remarked of these binary compounds of the four chief organic elements, that they are, on the average, less stable than binary com- pounds in general. Water, carbonic oxide, and carbonic acid, are, it is true, difficult to decompose. But omitting these, the usual strength of union among the elements of the above-named substances is low considering the simplicity * This immense loss of molecular mobility which oxygen and hydrogen un- dergo on uniting to form water—a loss far greater than that seen in other binary compounds of analogous composition—suggests the conclusion that the atom of water is a multiple atom. Thinking that if this conclusion be true, some evidence of the fact must be afforded by the heat-absorbing power of aqueous vapour, I lately put the question to Prof. & THE DATA OF BIOLOGY. of the substances. With the exception of acetylene, the various hydro-carbons are not producible by directly com- bining their elements ; and the elements of most of them are readily separated by heat without the aid of any antagonistic afiinity. Nitrogen and hydrogen do not unite with each other immediately ; and the ammonia which results from their mediate union, though it resists heat, yields to the electric spark. Cyanogen is stable: not being resolved into its components at a red heat, unless in iron vessels. Much less stable however are the several oxides of nitrogen. The protoxide, it is true, does not yield up its elements below a red heat; but nitrous acid cannot exist if water be added to it; hypo-nitric acid is decomposed both by water and by contact with the various bases; and nitric acid not only readily parts with its oxygen to many metals, but when anhydrous, spontaneously decomposes. Here it will be well to note, as having a bearing on what is to follow, how characteristic of most nitrogenous compounds is this special instability. In all the familiar cases of sudden and violent decomposition, the change is due to the presence of nitrogen. The explosion of gunpowder results from the readiness with which the nitrogen contained in the nitrate of potash, yields up the oxygen combined with it. The explosion of gun-cot- ton, which also contains nitric acid, is a substantially par- allel phenomenon. The various fulminating salts are all formed by the union with metals, of a certain nitrogenous acid called fulminic acid ; which is so unstable that it cannot be obtained in a separate state. Explosiveness is a property of nitro-mannite, and also of nitro-glycerin. Iodide of nitrogen detonates on the slightest touch, and often without any assign- able cause. Percussion produces detonation in sulphide of nitrogen. And the body which explodes with the most tremendous violence of any that is known, is the chloride of nitrogen. Thus these easy and rapid decompositions, due to the chemical indifference of nitrogen, are characteristic. When we come hereafter to observe the part which nitrogen ORGANIC MATTER. Ps] plays in organic actions, we shall see the significance of this extreme readiness shown by its compounds to undergo change. Returning from these facts parenthetically introduced, we have next to note that though among these binary compounds of the four chief organic elements, there are a few active ones, yet the majority of them display a smaller degree of chemical energy than the average of binary compounds. Water is the most neutral of bodies : usually pro- ducing little chemical alteration in the substances with which it combines ; and being expelled from most of its combinations by a moderate heat. Carbonic acid is a relatively feeble acid: the carbonates being decomposed by the majority of other acids and by ignition. The various hydro-carbons are but narrow in the range of their comparatively weak affinities. The compounds formed by ammonia have not much stability: they are readily destroyed by heat, and by the other alkalies. The affinities of cyanogen are tolerably strong; though they yield to those of the chief acids. Of the several oxides of ni- trogen it is to be remarked, that while those containing the smaller proportions of oxygen are chemically inert, that con- taining the greatest proportion of oxygen (nitric acid) though chemically active, in consequence of the readiness with which one part of it gives up its oxygen to oxidize a base with which the rest combines, is nevertheless driven from all its combinations by a red heat. These binary compounds, like their elements, are to a con- siderable degree characterized by the prevalence among them of allotropism; or, as it is more usually called when displayed by compound bodies—isomerism. Professor Graham finds reason for thinking that a change in atomic arrange- ment of this nature, takes place in water, at or near the melting point of ice. The relation between cyanogen and paracyanogen is, a3 we saw, an isomeric one. In the above- named series of hydro-carbons, differing from each other only in the multiples in which the elements are united, we find isomerism becoming what is distinguished as polymerism. 10 THE DATA OF BIOLOGY. The like is still more conspicuous in other groups of the hydro-carbons, as in the essential oils: sixteen to twenty of which are severally isomeric with essential oil of turpentine. Here the particular kind of molecular mobility implied by these metamorphoses, is well shown: essential oil of turpen- tine being converted into a mixture of several of these poly- merides, by simple exposure to a heat of 460°. There is one further fact respecting these binary compounds of the four chief organic elements, which must not be over- looked. Those of them which form parts of the living tissues of plants and animals (excluding water which has a me- chanical function, and carbonic acid which is a product of decomposition) are confined to one group—the hydro-carbons. And of this group, which is on the average characterized by comparative instability and inertness, these hydro-carbons found in living tissues, are among the most unstable and inert. § 3. Passing now to the substances which contain three of these chief organic elements, we have first to note that along with the greater atomic weight which mostly accor- panies their increased complexity, there is, on the average, a further marked decrease of molecular mobility. Scarcely any of them maintain a gaseous state at ordinary temperatures. One class of them only, the alcohols and their derivatives, evaporate under the usual atmospheric pressure; but not rapidly unless heated. ‘The fixed oils, though they show that molecular mobility implied by an habitually liquid state, show this in a lower degree than the alcoholic compounds ; and they cannot be reduced to the gaseous state without de- composition. In their allies, the fats, which are solid unless heated, the loss of molecular mobility is still more marked. And throughout the whole series of the fatty acids, in which to a fixed proportion of oxygen there are successively added higher equimultiples of carbon and hydrogen, we see how the molecular mobility decreases with the increasing sizes of ORGANIC MATTER. fa the atoms. In the amylaceous and saccharine group of com- pounds, solidity is the habitual state: such of them as can assume the liquid form, doing so only when heated to 500° or 400° F.; and decomposing when further heated, rather than become gaseous. Resins and gums exhibit general physical properties of like character and meaning. In chemical stability these ternary compounds, considered as a group, are in a marked degree below the binary ones. The various sugars and kindred bodies, decompose at no very high temperatures. The oils and fats are also readily carbon- ized by heat. Resinous and gummy substances are easily made to render up some of their constituents. And the alcohols with their allies, have no great power of resisting decomposition. These bodies, formed by the union of oxygen, hydrogen and carbon, are also, as a class, chemically inactive. The formic and .acetic are doubtless energetic acids ; but the higher members of the fatty-acid series are easily separated from the bases with which they combine. Saccharic acid, too, is an acid of considerable power; and sundry of the vegetal acids possess a certain activity, though an activity far less than that of the mineral acids. But throughout the rest of the group, there is shown but a small tendency to combine with other bodies; and such com binations as are formed have usually little permanence. The phenomena of isomerism and polymerism are of fre- quent occurrence in these ternary compounds. Starch and dextrine are isomeric. Fruit sugar, starch sugar, eucalyn, sorbin, and inosite, are polymeric. Sundry of the vegetal acils exhibit similar modifications. And among the resins and gums, with their derivatives, molecular re-arrangements of this kind are not uncommon. One further fact respecting these compounds of carbon, oxygen and hydrogen, should be mentioned; namely, that they are divisible into two classes—the one consisting of suo- stances that result from the destructive decomposition of organic matter, and the other consisting of substances that 12 THE DATA OF BIOLOGY. exist as such in organic matter. These two classes of sub- stances exhibit in different degrees, the properties to which we have been directing our attention. The lower alcohols, their allies and derivatives, which possess greater molecular mobility and chemical stability than the rest of these ternary compounds, are not found in animal or vegetal bodies. While the sugars and amylaceous substances, the fixed oils and fats, the gums and resins, which have all of them much less mole- cular mobility, and are, chemically considered, more unstable and inert, are components of the living tissues of plants and animals. | § 4. Among compounds containing all the four chief organic elements, a division. analogous to that just named may be made. There are some which result from the decom- position of living tissues; there are others which make parts of living tissues in their state of integrity ; and these two groups are contrasted in their properties in the same way as are the parallel groups of ternary compounds. Of the first division, certain products found in the animal excretions are the most important, and the only ones that need be noted; such, namely, as urea, kreatine, kreatimine. These animal bases exhibit much less molecular mobility than the average of the substances treated of in the last section: being solid at ordinary temperatures, fusing, where fusible at all, at temperatures above that of boiling water, and having no power to assume a gaseous state. Chemically considered, their stability is low, and their activity but small, in com- parison with the stabilities and activities of the simpler eom- pounds. It is, however, the nitrogenous constituents of living tis- sues, that display most markedly, those characteristics of which we have been tracing the growth. Albumen, fibrin, casein, and their allies, are bodies in which that molecular mobility exhibited by three of their components in so high a degree, is reduced toa minimum. These substances are known only ORGANIC MATTER. 13 in the solid state: that is to say, when deprived of the water usually mixed with them, they do not admit of fusion, much less of volatilization. To which add, that they have not even that molecular mobility which solution in water implies ; since, though they form viscid mixtures with water, they do not dissolve in the same perfect way as do inorganic com- ' pounds. The chemical characteristics of these sub- stances, are instability and inertness carried to the extreme. How rapidly albumenoid matters decompose under ordinary conditions, is daily seen: the difficulty of every house-wife being to prevent them from decomposing. It is true that when desiccated and kept from contact with air, they may be preserved unchanged for a long period; but the fact that they can only be thus preserved, proves their great instability. It is true, also, that these most complex nitrogenous principles are not absolutely inert; since they enter into combinations with some bases; but their unions are very feeble. It should be noted, too, of these bodies, that though they exhibit in the lowest degree that kind of molecular mobility, which implies facile vibration of the atoms as wholes, they ex- hibit in a high degree that kind of molecular mobility resulting in isomerism, which imples permanent changes in the posi- tions of adjacent atoms with respect to each other. Lach of them has a soluble and insoluble form. In some cases there are indications of more than two such forms. And it appears that their metamorphoses take place under very slight changes of conditions. In these most unstable and inert organic compounds, we find that the atomic complexity reaches a maximum: not only since the four chief organic elements are here united with small proportions of sulphur and phosphorus ; but also since they are united in high multiples. The peculiarity which we found characterized even binary compounds of the organic elements, that their atoms are formed not of single equivalents of each component, but of two, three, four and more equivalents, is carried to the greatest extreme in these 14 THE DATA OF BIOLOGY. compounds, that take the leading part in organic actions, According to Mulder, the formula of albumen is 10 (CO H N’ 0") + 8’ P. That is to say, with the sulphur and phos- phorus there are united ten equivalents of a compound atom containing forty atoms of carbon, thirty-one of hydrogen, five of nitrogen, and twelve of oxygen: the atom being thus made up of nearly nine hundred ultimate atoms. § 5. Did space permit, it would be useful here to consider in detail, the interpretations that may be given of the pecu- liarities we have been tracing: bringing to their solution, those general mechanical principles which are now found to hold true of molecules as of masses. But it must suffice briefly to indicate the conclusions that such an inquiry pro- mises to bring out. Proceeding on mechanical principles, it may be argued that the molecular mobility of a substance must depend partly on the inertia of its molecules ; partly on the intensity of their mutual polarities; partly on their mutual pressure, as deter- mined by the density of their aggregation, and (where the molecules are compound) partly on the molecular mobilities of their component molecules. Whence it is to be inferred that any three of these remaining constant, the molecular mobility will vary asthe fourth. Other things equal, there- fore, the molecular mobility of atoms must decrease as their masses increase; and so there must result that general pro- gression we have traced, from the high molecular mobility of the uncombined organic elements, to the low molecular mobility of those large-atomed substances into which they are ultimately compounded. Applying to atoms the mechanical law which holds of masses, that since inertia and gravity increase as the cubes of the dimensions while cohesion increases as their squares, the self-sustaining power of a body becomes relatively smaller as its bulk becomes greater ; it might be argued that these large, aggregate atoms which constitute organic sub- ORGANIC MATTER. 15 stance, are mechanically weak—are less able than simpler atoms to bear, without alteration, the forces falling on them. That very massiveness which renders them less mobile, enables the physical forces acting on them more readily to change the relative positions of their component atoms; and so to pro- duce what we know as re-arrangements and decompositions. Further, it seems a not improbable conclusion, that this formation of large aggregates of elementary atoms, and re- sulting diminution of self-sustaining power, must be accom- panied by a decrease of those contrasts of dimension to which polarity is ascribable. A sphere is the figure of equi- librium which any aggregate of units tends to assume, under the influence of simple mutual attraction. Where the num- ber of units is small and their mutual polarities are decided, this proclivity towards spherical grouping will be overcome by the tendency towards some more special form, determined by their mutual polarities. But it is manifest that in pro- portion as an ageregate atom becomes larger, the effects of simple mutual attraction must become relatively greater ; and so must tend to mask the effects of polar attraction. There will consequently be apt to result in highly com- pound atoms lke these organic ones containing nine hun- dred elementary atoms, such approximation to the spherical form as must involve a less distinct polarity than in simpler atoms. If this inference be correct, it supplies us with an ex- planation both of the chemical inertness of these most com- plex organic substances, and of their inability to crystallize. § 6. Here we are naturally introduced to another aspect of our subject—an aspect of great interest. Professor Graham has recently published a series of important researches, which promise to throw much light on the constitution and changes of organic matter. He shows that solid substances exist un- der two forms of aggregation—the collozd or jelly-like, and the erystalloid or crystal-like. Examples of the last are too fa- miliar to need specifying. Of the first may be named such 16 THE DATA OF BIOLOGY. instances as “hydrated silicic acid, hydrated alumina, and other metallic peroxides of the aluminous class, when they exist in the soluble form ; with starch, dextrine and the gums, cara- mel, tannin, albumen, gelatine, vegetable and animal extractive matters.” Describing the properties of colloids, Professor Graham says :—“ Although often largely soluble in water, they are held in solution by a most feeble force. They ap- pear singularly inert in the capacity of acids and bases, and in all the ordinary chemical relations.’ * * * ‘Al though chemically inert in the ordinary sense, colloids possess a compensating activity of their own arising out of their physical properties. While the rigidity of the erystal- line structure shuts out external impressions, the softness of the gelatinous colloid partakes of fluidity, and enables the colloid to become a medium of liquid diffusion, like water itself.” * * * ‘Hence a wide sensibility on the part of colloids to external agents. Another and eminently charac- teristic quality of colloids is their mutability.” * * * “The solution of hydrated silicic acid, for instance, is easily obtain- ed in a state of purity, but it cannot be preserved. It may remain fluid for days or weeks in a sealed tube, but is sure to gclatinize and become insoluble at last. Nor does the change of this colloid appear to stop at that point; for the mineral forms of silicic acid, deposited from water, such as flint, are often found to have passed, during the geological ages of their existence, from the vitreous or colloidal into the erystal- line condition (H. Rose). The colloid 1s, in fact, a dynami- cal state of matter, the crystalloidal being the statical condition. The colloid possesses energia. It may be looked upon as the primary source of the force appearing in the phenomena of vitality. To the gradual manner in which colloidal changes take place (for they always demand time as an element) may the characteristic protraction of chemico- organic changes also be referred.” The class of colloids includes not only all those most come plex nitrogeneous compounds characteristic of organic tissue, ORGANIC MATTER. 1? and sundry of the oxy-hydro-carbons found along with them ; but, significantly enough, it includes several of those sub- stances classed as inorganic, which enter into organized structures. Indeed, the coagulum of this colloid is highly suggestive of that of blood, from the feeble agencies which suffice to effect the change in question, as well as from the appearance of the product.” ‘The jelly thus formed soon becomes, like the last, insoluble in water. Lime also, which is so important a mineral element in living bodies, animal and vegetal, enters into a compound belonging to this class. ‘The well-known solution of lime in sugar, forms a solid coagulum when heated. It is probably, at a high temperature, entirely colloidal.” Generalizing some of the facts which he gives, Professor Graham says—‘“‘ The equivalent of a colloid appears to be always high, although the ratio between the elements of the substance may be simple. Gummic acid, for instance, may be represented by C”? H"™ O"; but, judging from the small proportions of lime and potash which suffice te neutralize this 2 18 THE DATA OF BIOLOGY. acid, the true numbers of its formula must be several times greater. It is difficult to avoid associating the inertness of colloids with their high equivalents, particularly where the high number appears to be attained by the repetition of a small number. ‘The inquiry suggests itself whether the col- loid molecule may not be constituted by the grouping together of a number of smaller crystalloid molecules, and whether the basis of colloidality may not really be this com. posite character of the molecule.” § 7. A further contrast between colloids and erystalloide, is equally significant in its relations to vital phenomena. Professor Graham points out that the marked differences in volatility displayed by different bodies, are paralleled by differences in the rates of diffusion of different bodies through liquids. As alcohol and ether at ordinary temperatures, and various other substances at higher temperatures, diffuse them- selves in a gaseous form through the air; so, a substance in aqueous solution, when placed in contact with a mass of water (in such way as to avoid mixture by circulating currents) diffuses itself through this mass of water. And just as there are various degrees of rapidity in evaporation, so there are various degrees of rapidity in diffusion: “ the range also in the degree of diffusive mobility exhibited by different sub- stances appears to be as wide as the scale of vapour-tensions.”’ This parallelism is what might have been looked for; since the tendency to assume a gascous state, and the tendency to spread in solution through a liquid, are both consequences of molecular mobility. It also turns out, as was to be expected, that diffusibility, like volatility, has, other things equal, a re- lation to atomic weight—(other things equal, we must say, because molecular mobility must, as pointed out in§ 5, be affected by other properties of atoms, besides their inertia). Thus the substance most rapidly diffused of any on which Professor Graham experimented, was hydro-chloric acid—a compound which is of low atomic weight, is gaseous save ORGANIC MATTER. 19 under a pressure of forty atmospheres, and ordinarily exists as a liquid, only in combination with water. Again, “hydrate of potash may be said to possess double the velocity of diffu- sion of sulphate of potash, and sulphate of potash again double the velocity of sugar, alcohol, and sulphate of magnesia,’’—- differences which have a general correspondence with differ- ences in the massiveness of the atoms. But the fact of chief interest to us here, is that the rela- tively small-atomed crystalloids have immensely greater diffusive power than the relatively large-atomed colloids. Among the crystalloids themselves, there are marked differ ences of ditfusibility ; and among the colloids themselves, there are parallel differences, though less marked ones. But these differences are small compared with that between the diffusibility of the crystalloids as a class, and the diffusibility of the colloids as a class. Hydro-chloric acid is seven times as diffusible as sulphate of magnesia ; but it is fifty times as diffusible as albumen, and a hundred times as diffusible as caramel. These differences of diffusibility manifest themselves with nearly equal distinctness, when a permeable septum is placed between the solution and the water. And the result is, that when a solution contains substances of different diffusibilities, the process of dialysis, as Professor Graham calls it, becomes a means of separating the mixed substances: especially when such mixed substances are partly crystalloids and partly col- loids. The bearing of this fact on organic processes will be obvious. Still more obvious will its bearing be, on joming it with the remarkable fact, that while crystalloids ean diffuse themselves through colloids nearly as rapidly as through water, colloids can scarcely diffuse themselves at all through other colloids. From a mass of jelly containing salt, into an adjoining mass of jelly containing no salt, the salt spread more in eight days than it spread through water in seven days; while the spread of “caramel through the jelly appeared scarcely to have begun after eight days had 20 THE DATA OF BIOLOGY. elapsed.’’? So that we must regard the colloidal compounds of which organisms are built, as having by their physical nature, the ability to separate colloids from crystalloids, and to let the crystalloids pass through them with scarcely any resistance. One other result of these researches on the relative diffu- sibilities of different substances, has a meaning for us. Pro- fessor Graham finds, that not only does there take place by dialysis, a separation of mized substances which are unlike in their molecular mobilities ; but also that combined substances between which the affinity is feeble, will separate on the dialyzer, if their molecular mobilities are strongly con- trasted. Speaking of the hydro-chlorate of peroxide of iron, he says, ‘‘such a compound possesses an element of instability in the extremely unequal diffusibility of its constituents ;’’ and he points out that when dialyzed, the hydro-chloric acid gradually diffuses away, leaving the colloidal peroxide of iron behind. Similarly, he remarks of the peracetate of iron, that it “‘may be made a source of soluble peroxide, as the salt referred to is itself decomposed to a great extent by diffusion on the dialyzer.” Now this tendency to separate displayed by substances that differ widely in their molecular mobilities, though usually so far antagonized by their affinities as not to produce sponta- neous decomposition, must, in all cases, induce a certain readiness to change which would not else exist. The un- equal mobilities of the combined atoms, must give disturbing forces a greater power to work transformations than they would otherwise have. Hence the probable significance of a fact named at the outset, that while three of the chief organic elements have the greatest atomic mobilities of any elements known, the fourth, carbon, has the least atomic mobility of known elements. Though, in its simple compounds, the affinities of carbon for the rest are strong enough to prevent the effects of this great difference from clearly showing theme selves ; yet there seems reason to think, that in those come ORGANIC MATTER. 21 plex compounds composing organic bodies—compounds in which there are various cross affinities leading to a state of chemical tension—this extreme difference in the molecular mobilities must be an important aid to molecular re-arrange- ments. In short, we are here led by concrete evidence to the conclusion which we before drew from first principles, that this great unlikeness among the combined units must facil- tate differentiations. § 8. A portion of organic matter in a state to exhibit those phenomena which the biologist deals with, is, however, something far more complex than the separate organic mat- ters we have been studying; since a portion of organic matter in its integrity, contains several of these. In the first place, no one of those colloids which make up the mass of a living body, appears capable of carrying on vital changes by itself: it is always associated with other colloids. A portion of animal-tissue, however minute, almost always contains more than one form of protein-substance : different chemical modifications of albumen and gelatine are present together, as well as, probably, a soluble and insoluble modification of each; and there is usually more or less of fatty matter. In a single vegetal cell, the minute quantity of nitrogenous colloid present, is imbedded in colloids of the non-nitrogenous class. The microscope makes it at once manifest, that even the smallest and simplest organic forms are not absolutely homogeneous. T‘urther, we have to contemplate organic tissue, formed of mingled colloids in both soluble and insoluble states, as permeated throughout by crystalloids. Some of these crys- talloids, as oxygen,* water, and perhaps certain salts, are agents of decomposition ; some, as the saccharine and fatty * Tt will perhaps seem strange to class oxygen asa crystalloid. But inasmuch as the crystalloids are distinguished from the colloids by their atomic simplicity, and inasmuch as sundry gases are reducible to a crystalline state, we are justified in so classing it, 22 THE DATA OF BIOLOGY. matters, are probably materials for decomposition; and some, as carbonic acid, water, urea, kreatine, and kreatinine, are products of decomposition. Into the mass of mingled colloids, mostly insoluble and where soluble of very low molecular mobility or diffusive power, we have constantly passing, erys- talloids of high molecular mobility or diffusive power, that are capable of decomposing these complex colloids; and from these complex colloids, so decomposed, there result other crystalloids (the two chief ones extremely simple and mobile, and the rest comparatively so) which diffuse away as rapidly as they are formed. And now we may clearly see the necessity for that pecu- lar composition which we find in organic matter. On the one hand, were it not for the extreme molecular mobility possessed by three of its chief elements out of the four; and were it not for the consequently high molecular mobility of _ their simpler compounds; there could not be this quick escape of the waste products of organic action ; and there could not be that continuously active change of matter which vitality implhes. On the other hand, were it not for the union of these extremely mobile elements into immensely complex compounds, haying. relatively vast atoms that are made com- paratively immobile by their inertia, there could not result that mechanical fixity which prevents the components of liv- ing tissue from diffusing away along with the effete matters preduced by the decomposition of tissue. § 9. Thus in the substances of which organisms are composed, the conditions necessary to that re-distribution of Matter and Motion which constitutes Evolution, are fulfilled in a far higher degree than at first appears. 