Émile-Honoré Cazelles

“ Considered in the light of this hypothesis, generation appears as a fact of disaggregation, occurring in an organism in process of equilibration: as a fact of disaggregation, which ever renews the evolution of the species, and which retards its equilibrium by multiplying the conditions under which the species may, under the influence of the incident forces of the environment, undergo a more perfect elaboration, the result of which shall be a better adaptation of the organism to its surroundings. ”

“ Biology can give no answer, unless we suppose that the genesis of individuals belongs as a genus to a class of facts including all the phenomena of general disintegration which attend growth, and which mark the gradual decline of the organism. This supposition finds its warrant in the fact that, as a general rule, reproduction does not take place until growth and structural development approach their term, when the molecular forces of the physiological units find themselves in equilibrium with the forces of the organism as a whole, and with the forces from without. ”

“ Again, we have the law of coördination and subordination of functions and organs, in virtue of which, in proportion as complexity is introduced into the organism and as the functions and organs take on a more special character, certain functions and the organs performing them become dependent on other functions and other organs. Besides, a tie of solidarity is established between all the parts of the living body, so as to guide them toward a common end, the conservation of the individual, while at the same time all of the parts feel the reverberation of the actions to which each is subject. ”

“ By another law, flowing from the same primary principle, the parts of a whole diverge from one another in proportion to their diversity, and group themselves together in proportion to their resemblances. ”

“ The integration by an organism of substances homologous with its own has for its effect a segregation which increases the difference between the organism and the environment, and at the same time makes this difference stable. While the organism is being integrated, at the expense of the environment, by deriving from it special materials, each organ is being integrated at the expense of the organism, from which it derives, as from an environment, its special materials. Like the organism, each organ diverges more and more, by a gradual segregation, from the organs around about it. ”

“ But in justice to those who maintain the precedence of structure, it must be added that function, which, as we hold, is anterior to structure, nevertheless, regarded as an activity modified and different from what it was, assumes its differential, distinguishing characters only in proportion as the adaptation becomes perfect, and as equilibrium is established between that portion of internal reaction which it represents and the external action which it withstands. ”

“ But differentiation is not the only change produced in the organism. The functions, as they multiply and are better defined, combine, become dependent on each other, are integrated. Labor is divided, as they say in political economy, but it is also centralized, and coordinated. Alongside of division of labor we have coöperation: an organ does not work for itself alone; it has a special function, but this function serves to facilitate, or even to render possible, the special function of some other organ. ”

“ The universal synthesis which is to constitute philosophy must express the total operation accomplished by the cooperation of these factors. The law which shall formulate this synthesis must be a law of the changes in forces under the two phases, matter and motion, by which they are manifested to us: it must be a principle of dynamics holding good both for the whole of the cosmos, and for its every detail. The changes of an object are all produced by new arrangements of the matter constituting it, and by a new distribution of the forces which belong to it. ”

“ But agamo-genesis is not habitual in organisms of very simple structure, which exhibit the first steps in evolution, and in which the absence of highly-specialized tissues shows that integration still possesses its full intensity, and is far removed from equilibrium. Besides, those more complex organisms which exhibit the phenomenon of agamo-genesis, from time to time reproduce by way of gamo-genesis. After a series of agamic generations, the units of the organism will find themselves in an attitude approaching that of mutual equilibrium. ”

“ BIOLOGY, or the science of life, is so new a subject of investigation that its limits are as yet imperfectly ascertained. Metaphysical ideas have too large a place in our conception of its extent. When we ask where biology commences, we are met by the problem of the origin of living: things. which very often is solved in accordance rather with preconceived opinions of the system of the universe than with an independent scientific hypothesis. When we would determine its limits, we are met by the problems of cognition, and of the causes determining man's actions ”

“ The old conception of living Nature as an infinitely varied assemblage of organisms which faithfully copy certain types, all of whose parts are governed by the law of final causes, in our time gives way, not without a fierce struggle, before a new conception, which represents living Nature as an infinitely varied assemblage of organisms which are ever varying under the influence of external circumstances, while under the influence of heredity they tend to fix in a type the results of previous variations. ”

“ If the starting-point be homogeneity, and if the transition from a structureless to a structural state is a phenomenon of vital action, then vital action precedes structure. Life is a system of internal actions adapted to equilibrate external actions; actions are the substance of life, its form comes from structure. Hence action must of necessity precede the fixation of the structure, which produces the adaptation and gives definite form to the function. From first to last, function is the determining cause of structure. ”

“ If this doctrine is to be retained, it is not for the purpose of explaining the formation of organisms, a thing well enough explained without it, but in order to account for the production of really primitive living things—i. e., for the appearance of life in a fraction of organic substance, whether this is still possible in our day, or whether it was possible only at a time when, under conditions unknown to us, organic substance originated upon the earth. Thus stated, the question does not depend on experimentation; it becomes a mere exercise of the imagination, and the result is valueless. ”

“ Finally, we note another consequence of the persistence of force. Every change in an aggregation of sensible parts is conditioned by opposing forces, the one representing action, the other reaction; the one the tendency to change, the other resistance; their antagonism can end only when equilibrium has been established, by the dissipation of the excess of the one force over the other. A body subject to any disturbance whatever, owing to a modification of its circumstances, tends toward equilibrium with its new circumstances ”

“ In reality, the contrasts are in excess of the analogies; generation is at bottom an operation of disintegration. This is very well seen in those low organisms which produce new generations by fission, and abdicate their individuality in favor of a greater or less number of new individualities. It is also to be seen in those organisms on whose surface a new organism is formed by the process of budding. Here the disintegration is perfect, or nearly so, but in the higher organisms the disintegration affects only an insignificant portion of the parent. ”

“ Thus we see that, in virtue of the general laws set forth in the "First Principles," an adaptive change must quickly find a term beyond which it cannot progress save slowly—a fact which explains the apparent fixity of species, or the inconsiderableness of such deviations from a type as can occur during the periods over which our observations extend. It is plain that a modifying cause, the action of which persists only for a short time, can produce only a transient modification ”

“ In more recent times biology has been enriched with an enormous amount of facts for which we are indebted to the labors of naturalists, or even of mere breeders, as also to the labors of anatomists and clinicians, but, above all, to researches in experimental physiology, wherein the application of physical-science methods to the discovery of the laws of vital phenomena has been attended with brilliant success. ”

“ Still, in spite of these difficulties, though we cannot say precisely what life is, where its province commences, where it ends, there exists between the two extremes—the inorganic world and the mental world—a very firm ground, imperfectly explored, it is true, but nevertheless belonging to biology alone. The various departments which constitute this domain, though they themselves are not all very clearly defined, are sufficient to give to biology a definite individuality.
Living things present themselves to the observer of Nature as individuals ”

“ The increase of function in these organs once established by a definite structure, the organ A not only can preserve its increase of structure and function, but it has now a firmer basis for growing still more, for producing another excess of function, and for going farther in the same direction than otherwise it could have gone. But adaptive modifications have a limit, and it is always near at hand, though it slowly retreats from generation to generation. This we learn from the mechanism of adaptation. ”

“ First, we have the law of the increase of the mass of the organism, in virtue of which each living thing attains its full development only by passing through a series of phases characterized by an augmentation of its mass, and consequently by an augmentation of the quantity of force applicable for its physiological actions, as also by an augmentation of the quantity of functional products. ”

“ At the same time, by comparing and analyzing the different branches of biology, certain very general laws have been established, particularly in physiology proper, having a bearing upon the development of the individual and the relations of the functions to their organs. We are in possession of a certain number of very broad though purely empiric generalizations on the phenomena upon which the superiority of living things over one another depends. ”

“ The belief which from day to day is gaining confirmation from the labors of physiologists is that so boldly expressed by Claude Bernard, viz., that as the chemist, starting with the knowledge of inorganic bodies, subjects them to his will and creates new bodies, so the physiologist, starting from organic matter, "by imposing upon it special conditions, will be able to produce new physiological modifications and new series of phenomena, thus modifying at will living-bodies, and even creating them." ”

“ Such are, in brief, the principal laws of biological phenomena, and the chief theories which have been devised for the purpose of assigning to them causes. When, in order to establish or to impugn laws and theories so far-reaching as these, we can have recourse to direct experiment and observation, the mind is satisfied and its certitude reposes on an immovable basis. But when a theory has to do with origins in the remote past, or even in the present, but inaccessible to experiment, our certitude rests on no solid foundation. ”

“ In addition to an immense amount of unquestionable facts, in addition to a knowledge of the elementary properties of organic tissues and an acquaintance with the special laws which represent the action of these tissues in presence of these modifiers, this general result has followed the conquests of biology, namely, that living bodies are now known to be subject to the self-same laws which govern inorganic bodies, and that, under the hand of the experimenter, the course of things within the tissues is precisely the same as without the tissues ”

“ But on the theory of evolution we can conceive of another mode of formation. It is possible that even now, under existing cosmical conditions, organic matter is produced; but it is more probable that it was formed in an epoch when the cosmical forces now known to us, especially heat and light, had on earth a greater intensity than at present. The first types must have been more simple, less definite, less fixed in form and structure, than the lowest rhizopods of our day. ”

“ The question as to how living bodies are produced gave rise, a few years ago, to discussions which have again brought to the surface a doctrine which was supposed to have been disproved two hundred years since, and which reappeared in the last century only to be assailed with Voltaire's sarcasms. I mean the theory of spontaneous generation, so called—a self-contradictory phrase, by which it was intended to assert that organisms are produced out-and-out without the aid of parents resembling them. ”

“ When men of science had begun to study living things with other purposes than simply that of deriving from them knowledge that would be available for the medical art, and had gained sufficient information for inductive generalizations, they no longer contented themselves with theories of the origin of groups, but sought to reduce to general principles the structure of living bodies—a thing which previously had been considered only from the topographical point of view, and with reference to what was called the use of the parts ”

“ But in a very large number of organisms, and in all higher organisms of both the organic kingdoms, reproduction takes place by the mixture of two products, the one germinal, the other spermatic, coming from slightly different physiological units. In virtue of a property found in the simplest organic elements, and still more markedly present in the complex organic elements of living things, the mixture of substances which differ little from one another gives rise to products that are less stable than their constituent elements. ”

“ As the function of an organ cannot be permanently increased save on condition that the functions of those organs on the action of which it depends have gained a permanent increment, and as they in turn are conditioned on a permanent increment in the functions of other organs, it is plain that there is needed nothing short of a reconstruction of the whole organism upon a plan which shall insure normal provision for the organ that is subject to an excess of function, and in which this excess of function shall be in fact a normal process. ”