The Fitness of the Environment

nomical phenomena.^ And recent most re- markable studies of the stars have enabled astronomers to account for obscure events in far distant parts of the universe by the application of the principles of dynamics. Similarly light, heat, and chemical energy, as we know them, are unquestionably universal. No doubt the manifestations of energy within the sun and stars, like the accompany- ing material phenomena there, can to-day only be surmised. For aught we know, these places may, as has been guessed, be the birthplace of elements and the seat of mani- festations of energy quite different from

^ "What the Occasion of Sir Iscloc Newton's leaving the Cartesian Philosophy, and of discovering his amazing Theory of Gravity was, I have heard him long ago, soon after my first Acquaintance with him, which was 1694, thus relate, and of which Dr. Pemberton gives the like Account, and somewhat more fully, in the Preface to his Explication of his Philos- ophy: It was this. An Inclination came into Sir Isaac's Mind to try, whether the same Power did not keep the Moon in her Orbit, notwithstanding her projectile Velocity, which he knew always tended to go along a strait Line the Tangent of that Orbit, which makes Stones and all heavy Bodies with us fall downward, and which we call Gravity f Taking this Postulatum, which had been thought of before, that such Power might decrease, in a duplicate Proportion of the Dis- tances from the Earth's Center." — "Memoirs of the Life of Mr. William Whiston by Himself." London, 1749, Vol. I, pp. 35-38. Quoted by Ball. "An Essay on Newton's Prin- cipia." London, 1893, p. 8.

what we have ever observed. But, however interesting and important such processes may be, it is not to be supposed that they are of direct moment in physiological processes. These conditions are far beyond the limits of our present investigation. Accordingly, everything that observation has taught con- firms the belief that energy, like matter, is in general well known to us. Its manifesta- tions are few, and they are universal. But just as the generalizations of science yield further assurance regarding matter, so they do not fail to confirm our conclusions in the study of energy. The law of the conserva- tion of energy and the law of the degradation of energy, otherwise known as the first and second laws of thermodynamics, clearly in- dicate that the manifestations of energy are not accidental nor independent of one an- other. They are orderly, and they obey laws. Energy is one and indestructible.

Such are the apparently irrefragable con- clusions of the brief half century of creative development, from the time when Young first used the word "energy" and Bolton and Watt first employed the idea of measuring energy in horse power, through the period of Carnot's brilliant intuition regarding the ref- lation between heat and work, to the epoch of the foundation of thermodynamics.'^ To- day we know that just so much heat, neither more nor less, may be obtained by the com- plete conversion of a unit of electrical energy or by a given chemical process. We know, moreover, that not every conceivable change from one form of energy to another is possible. On the whole, energy can flow in but one direction; perpetual motion is impossible; and useful energy is steadily becoming de- graded, dissipated, and useless.

Such laws are fully worthy of a place be- side the periodic law, and they justify equal confidence in the adequacy of our current descriptions of matter and of energy for the piuposes of biology. Since Kant revolutionized modern phi- losophy, the whole world has steadily realized that between matter and energy on the one hand, and space and time on the other, there is a real and highly significant difference.^ ^ An excellent account of this period may be found in Merz's "History of European Thought in the Nineteenth Century," Vol. U, Chap. VII, "On the Physical View of Nature."

^ For a brief statement of Kant's argument see Royce, "The Spirit of Modern Philosophy," pp. 121-125. But, however important such distinctions may be for the philosopher, the man of science in his practical task is obliged to put them aside and to make the best of whatever evi- dence experience, observation, and experi- ment may supply. Out of such studies space and time have emerged, usefully defined by mathematical criticisni as substantial parts of the edifice of science.^

There is no small difficulty in the exposi- tion of modern critical results regarding space and time, but fortunately there is little need of considering them on the present occasion. For in spite of all assaults of phi- losophers and mathematicians space remains for practical purposes more certainly than ever the Euclidian space of the ancients, only it has become somewhat richer in char- acteristics. And time is now and forever that which flows equably, wholly independ- ent of all else, though almost all else is , dependent upon time. It is Euclidian space in which the earth moves and describes its ellipse, parallel rays of light never do meet in our practical experience, and our crystals

1 The works of Poincare, "La Science et THypotli^e," "La Valeur de la Science," and "Science et M6thode," published by Flammarion, may be consulted for a/^opular statement of such mathematical studies. are in form the figures of Euclidian geometry. Our time flows ever in proportion to the swings of a pendulum, the propagation of light, and the progress of a chemical change. Time and space are thus bound to matter and energy by experience, and for practical purposes we accept all four as science at present knows them.^ We cannot doubt that knowledge of them will increase and ideas of them change. But we can scarcely think that our present ideas are inadequate for our present purposes, or that, for life, matter will ever be other than the elements of the periodic classification, energy that set of quantities to which we apply the laws of thermodynamics, and time and space the concepts which were familiar to Galileo and Euclid.

Thus the growth of physical science has provided the speculative biologist with a very accurate and extensive description of the physico-chemical structure of the ma- terial universe and with a well-founded con- ^ In the present work we need have no concern for the so-called principle of relativity. fidence in his right to make use of the descrip- tion in investigating the relationship between life and the environment. The biologist studies living organisms as inhabitants of this world, and by holding fast to physics and chemistry he has created modern physiology, a science which unites many, indeed nearly all, of the departments of physics and chemistry in the task of de- scribing the processes of life.

That task has proved an arduous one, even in comparison with the other enterprises of science, and it must be confessed that few of the depiartments of physiology wear an aspect of finality which has long been famil- iar in Such sciences as mechanics and crystal- lography, for example. Yet, as time has passed, and the nature of the material basis of life and the conspicuous features of the mechanism which the organism presents for study have become more familiar, assurance has steadily grown of the possibility of decid- ing upon fundamental and essential char- acteristics of the life process. No doubt opinions have fluctuated, and in diflferent periods of the history of science particular phenomena of living organisms have been examined, criticized, and then well-nigh for- gotten. But gradually ideas, ever more and more precise, have arisen and been accepted.

Until very recent times, however, the main interest has centered upon morpho- logical problems and upon the processes of growth and development. The ancient con- troversies regarding types and homologous parts, the question of spontaneous genera- tion and the whole science of embryology, and inquiries into the nature of fermentation and the role of microorganisms are examples of the older tendencies. Such interests have, it need hardly be said, lost none of their im- portance, but they scarcely touch the physico- chemical problem of the nature of living things. Yet there is in these subjects one point of view, a favorite of Cuvier's, now, though still familiar, less often emphasized, which states a most important characteristic of life in terms of matter and energy, space and time.^ Living things preserve, or tend

* "La vie est done un tourbillon plus ou moins rapide, plus ou moins complique, dent la direction est constante, et qui entratne toujours des molecules de mSmes sortes, mais ou les molecules individueUes entrent et d'ou elles s&rtent continuellement, de maniere que la forme du corps vivant lui est plus essentielle que la matiere." ("Regne animal," p. 13, etc.) "II vient sans cesse des elements du dehors en dedans : D s'en echappe du dedans en dehors : toutes les par- ties sont dans un tourbiUon continual, qui est une condition essentielle du phenomene, et que nous ne pouvons suspendre longtemps sans I'arrSter pour jamais. Les branches les plus simples de I'histoire naturelle participant deja a cette compli-

to preserve, an ide£(,l form, while through them flows a steady stream of energy and mat- ter which is ever changing, yet momentarily molded by life; organized, in short. This idea, to which we must later return, could not possess in the early nineteenth century the significance and value which now attach to it. It needed the explanation which the study of metabolism has at length provided. Metabolism is the term applied to the in- flow and outflow of matter and energy and their intermediary transformations within the organism. Its serious investigation began with Lavoisier, the principal founder of mod- cation et a ce mouvement perp6tuel, qui rendent si difiBcile rapplication des sciences generales. " (" Rapport," p. 150, etc.) " Dans les corps vivans chaque partie a sa composition propre et distincte ; aucune de leurs molecules ne reste en place ; toutes entrent et sortent successivement : la vie est un tour- billon continuel, dont la direction, toute compliqu6e qu'elle, est, demeure constante, ainsi que I'espece des molecules qui y sent entralnees, mais non les molecules individuelles elles- mSmes. . . . Ainsi la forme de ces corps leur est plus essentielle que leur matiere," etc. (^Ibid. p. 200.) — "Eloges historiques," Vol. I, p. 200. Quoted by Merz, "A History of European Thought in the Nineteenth Century," Vol. I, p. 1294 Edinburgh and London, 1898.

ern chemistry, who by ingenious experiments discovered that the essential feature of the chemical process in the animal is combus- tion or oxidation, and that the amount of oxy- gen required by such combustion is not much less than that needed to burn substances which resemble the foods in the air. The problems which thus arose have been studied by a host of later investigators, notably by Liebig and Voit, and gradually a vast array of facts concerning the turnover of matter and en- ergy in the body have been accumulated. Among other achievements is the proof that the principle of the conservation of energy applies to the living organism. These have been chemical investigations, carried out by chemists, and for that reason, until quite recently, they have not received their due in general biology.

Meantime, as knowledge of the balance sheet of the body, the total metabolism so- called, has been perfected, more and more interest has developed in the changes which attend the passage of matter and energy in their various stages through the organism. Such problems at once demand a physico- chemical description of protoplasm as a nec- essary basis for their solution. The same demand has also arisen in other quarters. Thus the microscope, with all its brilliant contributions to knowledge of the form and more gross structural elements of the cell, hardly at all contributes to knowledge of its physico-chemical organization as a mechan- ism. Out of such needs a preliminary, if very imperfect, rational description of proto- plasm has arisen, and gradually the physical and chemical laws governing protoplasm, its form, composition, and stability, its con- stituent parts and their mode of action, and the physical and chemical changes within it are being discovered.^ The idea of dur- able form in matter and energy that change can now be applied to the cell with greater advantage, in that descriptions of the form and of the change are now at hand, though as yet all too imperfect.

Another profoundly important contribu- tion of the science of metabolism to our knowledge of the characteristics of life is the discovery of the cycle of matter through plants and animals.^ The plant takes up carbonic acid and water and a few other simple substances from air and soil," and 1 This subject is extensively treated by Hober, "Physik- alische Chemie der Zelle imd der Gewebe." Leipzig, 1911, 3ded. transforms them into oxygen, which renews the air, and sugar, starch, and other sub- stances, which are the food of the animal.^ These products the animal burns, thereby forming once more carbonic acid and water, which return to the plant and so pass through the cycle again and again. The changes in energy which accompany this process are quite different from the chemical changes. Starch and sugar and oxygen, formed in the leaf of the plant, are compounded of carbonic acid, water, and sunshine. This sunshine, or solar energy, wh'en changed into the chemical energy of the carbohydrate, is pre- served and transmitted to the animal.^ In his body it is set free as muscular force and heat, and then dissipated. ' Accordingly, when carbonic acid and water are combined to form sugar and oxygen in the leaf, it is al- ways a new store of solar energy which they bear, and while matter goes round and round, energy is being constantly degraded and lost. The one process is cyclic, the other moves steadily in one direction from

^ Our knowledge of photosjmthesis is largely based upon the classical work of N. T. de Saussiu-e, "Eecherches Chi- miques sur la Vegetation." Paris, 1804. 2 Only after the establishment of the principle of the conservation of energy was it possible to gain a clear con- ception of the energetics of metabolism. Independent alike of general biology and of the science of metabolism there has grown up still another department of natural sci- ence, organic chemistry, which contributes very materially to the description and com- prehension of living things. During a large part of the nineteenth century the efforts of chemists were mainly directed to the cultiva- tion of this subject, which seeks to describe the molecular constitution of all the com- pounds of carbon, including nearly all the individual substances which make up animals and plants. Gradually, as organic chemis- try has progressed, very complete descrip- tions of the atomic groupings within the molecules of fats,^ carbohydrates,* and pro-'

' Here, as in so many other cases, it is not the conservation of matter and energy, but the conservation of matter and the degradation of energy which are important. For an exten- sive development of this important difference see B. Brunhes, "La Degradation de I'Energie." Paris, 1909. ^ Chevreul, "Recherches Chimiques sur les Corps Gras." Paris, 1823. ^ E. Fischer, " Untersuchungen Uber Kohlenhydrate imd Fermente." Berlin, 1909. teins/ the chief of such things, and most of the other biologically important sub- stances have been obtained, and we are at length in possession of exceedingly clear and reliable ideas as to the chemical constitu- tion of living matter. In fact, the nature and laws of the chemical composition of pro- toplasm are actually more certain than the nature and laws of its physical structure.^

In this manner, by slow degrees, the de- scription of living things has progressed, and gradually the characteristics of life have become less obscure and their aspects more simple. It cannot be denied that many traits like consciousness and inheritance are, at least for the present, beyond the scope of description in terms of matter and energy, and the fundamental riddle shares this de- tachment.' But the physico-chemical basis * E. Fischer, " Untersuchungen tiber Aminosatiren, Poly- peptide und Proteine." Berlin, 1906.

^ Substantial progress in the latter field is nearly all of very recent date, almost whoUy since the sudden rise of physical chemistry. ' "But now, having confessed that Life as a principle of activity is unknown and unknowable — that while its phe- nomena are accessible to thought the implied noumenon is inaccessible — that only the manifestations come within the range of our intelligence while that which is manifested lies beyond it; we may resume the conclusions reached in the preceding chapters. Our surface knowledge continues to be

of life is firmly established in the world of our senses. On the whole the composition of living matter, its physical structure, the changes of matter and energy which consti- tute the metabolic process, together with the totality of such changes, which make up the fundamental economic process of that largest community which consists of all living beings, are all clearly defined. Under the circumstances it is certainly no rash enterprise to seek a definition of some of the essential characteristics of life. Al-

a knowledge of its kind, after recognizing the truth that it is only a surface knowledge. "For the conclusions we lately reached and the definition emerging from them, concern the order existing among the actions which living things exhibit ; and this order remains the same whether we know or do not know the nature of thaj from which the actions originate. We found a distinguish- ing trait of Life to be that its changes display a correspond- ence with coexistences and sequences in the environment; and this remains a distinguishing trait, though the thing which changes remains inscrutable. The statement that the continuous adjustment of internal relations to external relations constitute Life as cognizable by us, is not invali- dated by the admission that the reality in which these rela- tions inhere is incognizable." — Herbekt Spencer, "The Principles of Biology." New York and London, 1909, Vol. I. Revised and enlarged edition, pp. 122-123.

though it is probably far beyond our present power to make a complete study of the prob- lem, I feel sure that a brief analysis will justify certain very definite conclusions. Life as we know it is a physico-chemical mechan- ism, and it is probably inconceivable that it should be otherwise.^ As such, it possesses, and, we may well conclude, must ever pos- sess, a high degree of complexity, — physi- cally, chemically, and physiologically; that is to say, structurally and functionally. We cannot imagine life which is no more complex than a sphere, or salt, or the fall of rain, and, as we know it, it is in fact a very great deal more complex than such simple things. Next, living things, still more the community of living things, are durable. But complexity and durability of mechanism are only pos- sible if internal and external conditions are stable. Hence, automatic regulations of the environment and the possibility of regulation of conditions within the organism are essen- tial to life. It is not possible to specify a large number of conditions which must be regulated, but certain it is from our present experience that at least rough-segtiiat-ien-of

' I mean, of cours&>for the purposes of physical and chem- ical study. With such qualifications the statement is prob- ably no longer open to objection from any quarter. temperature, pressure, and chemical consti- tution of environment and organism are really essential to life, and that there is great advantage in many other regulations and in finer regulations. Finally, a living being must be active, hence its metabolism must be fed with matter and energy, and accordingly there must always be exchange of matter and energy with the environment.

Returning to the concept of the organism as a durable form through which flow matter and energy, it is now possible to make these ideas more vivid. The complex structure of the living being is relatively stable, alike in the chemical composition of its individual constituent molecules, in their proportions and amounts, in their aggregation into the invisible structural elements of protoplasm, in the visible parts of the cell, in the organs and tissues, and finally in toto, as a man or a tree. Similarly stable are the physical con- ditions within this structure: temperature, pressure, alkalinity, and osmotic pressure. Finally, that which surrounds it, the imme- diate environment, possesses also a high de- gree of stability, or if the organism be very complex, it may be that it has an efficient pro- tection against change of environment; a skin which insulates, for instance. But in this case

it has also acquired an environment, a milieu inUrieur for its cells, — like the blood and lymph, — which serves the same purpose as stability of the external environment, and ex- ercises the further function of supplying food. It is through this structure, in the process of metabolism, that matter and energy flow. Entering in various forms and quantities, they are temporarily shaped exactly to the form and condition of the organism; they conform to the characteristics of the king- dom, class, order, family, genus, species, and variety to which it belongs, and they assume even the characteristics of the in^vidual itself.^ Then they depart through th6 va- rious channels of excretion.

When these ideas are reduced to their very simplest forms, it appears that life must be highly complex in structure and function; that the conditions of the environment must be regulated, and that there must be very exact regulation of conditions, both structural and functional within the organism, and finally, that, while life is active, there must be ex- change of both matter and energy with the environment. Complexity, regulation, and food are essential to life as we know it, and

^ Science is, of course, still at a loss for an adequate gen- eral explanation of such processes. in truth we cannot otherwise conceive of life, or indeed of any other durable mechanism. For my part I do not doubt that these pos- tulates are quite as true of the world of our senses as are the fundamental laws of matter and energy, space and time. Obviously these few conclusions can make no claim to completeness. Fully to describe life, the discovery of many other fundamen- tal characteristics is necessary, including such as are related to inheritance, variation, evo- lution, consciousness, and a host of other things. But in the formation and logical development of such ideas there is danger of fallacy at every step, and since the present list will suffice for the present purpose, further considerations of this sort are best dispensed with. This subject should not be put aside, however, without clear emphasis that the postulates which have been adopted above are extremely meager. The only motives for abandoning further search are the economy and the security which are thus insured, and the very great difficulty of extending the list. Any one who is familiar with similar efforts to elucidate the essential character- istics of life, such as that of Wallace,^ cannot, I fear, fail to perceive the extreme limitations

which are imposed upon inquiry by assuming complexity^reg]ilaiion,--«,H:dr-m«%arb&Usffl--ex=^ clusively. Perhaps in reaUty these postu- lates are only two. Metabolism might with- out difficulty be included under regulation, but the consideration of such purely logical questions is beside the present purpose. However, these are probably the character- istics of the organism which are best fitted for discussion in relation to the physico-chemical phenomena of matter and energy, and it is barely possible that no others bear the same simple relations to the outside world.

York, 1903, Chaps. X and XI, especially the following statement : — "The physical conditions on the surface of our earth which appear to be necessary for the development and main- tenance of living organisms may be dealt with under the fol- lowing headings : — " 1. Regularity of heat supply, resulting in a limited range of temperature. "4. An atmosphere of sufficient density, and consisting of the gases which are essential for vegetable and animal life. These are Oxygen, Carbonic-acid gas. Aqueous vapor. Ni- trogen, and Ammonia. These must all be present in suitable proportions.