For the logical perfection of science, Comte prefers to regard species as fixed in the absence of contrary proofs. None the less Lamarck has stated a problem of the highest interest. Comte points out its importance. “The rational theory of the necessary action of the various milieux on the different organisms has still almost entirely to be formulated. Such an order of research, although greatly neglected, constitutes one of the finest subjects which the present condition of biology can present.” By this means, he adds, we might obtain a theory for the perfecting of living species even including mankind.[170]
V.
Comte’s anatomical and physiological philosophy is naturally allied to the science of his time. It is especially connected with the labours of Bichat and of de Blainville. Here again he endeavours to state the problems in the most general form possible. Anatomy should begin by the study of the tissues, to ascend afterwards to the association of several tissues, that is to say, to the organs, and to the associations of several organs, that is to say, to systems. But analysis must not be concerned with the tissue itself. To attempt the passage from this notion to that of the molecule, is to allow the organic to enter into the inorganic philosophy. In biology, the tissue corresponds to what the molecule is in physics. Such, at least, is the doctrine of the Cours de philosophie positive. Later on, instructed by Schwann’s works, Comte admits in the Politique positive that the anatomical element is the cell.
Be it tissue or cell, there must be a fundamental anatomical element. The simultaneous existence of several elements independent of one another would greatly mar “the admirable unity of the organic world,” and consequently the perfection of biological science. Life is always essentially the same. To this dynamic consideration, there must correspond, in the static order, that of a common basis invariable in its primordial organisation, successively producing, by deeper and deeper modifications, the various special anatomical elements.
Similarly, physiology will not be entirely organised until it studies functions (at least the organic functions), throughout the whole chain of living beings, from the vegetable kingdom up to man. This conception of a general physiology leads Comte to dwell, as Claude Bernard will later on, upon the phenomena of life which are common to plants and to animals. Some are better studied in plants and others in animals. But, whether it be animal or vegetable every organism always presents two fundamental functions: 1. the absorption of nutritious materials borrowed from the milieu (the assimilation of these materials and finally nutrition); 2. the rejection of unassimilated materials. However, plants are the only organised beings which live directly upon the inorganic milieu.[171] Comte was ignorant of the physiology of fungi.
Comte unreservedly adopts the distinction established by Bichat between the functions of organic life and those of animal life. In the first place he concludes from this, in virtue of the correlation of the dynamic to the static point of view, that distinct tissues correspond to these distinct functions. Then, he goes more deeply into the difference between the two kinds of functions. Strictly speaking, the phenomena of organic life only constitute a special order of composition and of decomposition. They come very near to chemistry, and may serve as a transition between the inorganic world and the world of life.[172] On the contrary, the phenomena of animal life (irritability, sensibility), offer no analogy with the phenomena of the inorganic world. We might almost believe, according to Comte, that the separation is established not between the chemical and biological phenomena, but between organic and animal life, the phenomena of the former reducing themselves to physico-chemical phenomena, and those of the latter presenting entirely different characteristics. Such is not, however, Comte’s thought. Undoubtedly, considered one by one, the phenomena of organic life (absorption, circulation, exhalation, etc.) are indeed physico-chemical phenomena. But what renders their biological character irreducible is that it is impossible to consider them separately: in order to understand them we must first look at them from the point of view of the whole, and appeal to the organic consensus, in a word, to what Claude Bernard, will call l’idée directrice.
In the study of organic functions we shall begin by the lower extremity in the series of living beings, that is to say by the most rudimentary forms of the vegetable kingdom, for it is here that we shall grasp the phenomena in their simplest form. Then we shall follow their growing complexity. For the animal functions, on the contrary, it is expedient to begin by man, “the only being in which such an order of phenomena is ever immediately intelligible.” From this point of view man is pre-eminently the biological unity. As soon as it is a question of the characteristics of animality, we must begin with man and see how they descend by degrees, rather than start from the sponge, and look for their mode of development. Man’s animal life helps us to understand that of the sponge; but the reverse is not true.[173] Moreover, the phenomena of organic life, being the most general, are also the most fundamental. The functions of animal life are first useful for the needs of organic life, by perfecting it. It is in man alone that the vegetative life is subordinate to the life of relation: and even for that he must have reached a high degree of civilisation.[174]
VI.
It is not surprising that biology, even more than physics and chemistry, preserves the metaphysical spirit. Such, for instance, is the hypothesis of spontaneous generation. Positive philosophy recognizes that each living being always emanates from another similar being. This is not established a priori, but is the result of an “immense induction.”[175] Omne vivum ex vivo. Efforts to explain how the generating tissue should itself be formed by kinds of organic monads, (an allusion to certain theories arising out of Schelling’s philosophy) can only fail. We should never know how to connect the organic with the inorganic world except through the fundamental laws belonging to the general phenomena which are common to them both. Positive speculations in anatomy and in physiology form a limited system, within which we must establish the most perfect unity, but which must ever remain separated from the whole of inorganic theories.[176] We see clearly, it is true, that there is no matter which is of itself living. Life is not peculiar to certain substances which are organised in a certain manner. It never belongs to them for more than a time: every organism of which the molecules are not renewed is dissolved. But “we can no more explain this instability than this speciality.”[177]
In the same way we see that in living bodies the nutritive functions are the basis of the others; but there is no contradiction in “dreaming” of thought and sociability in beings whose substance would remain unalterable. From this point of view spiritualism is not less admissible than materialism, in so much as death does not seem to be a necessary consequence of life. This again is an idea which is common to Descartes and to Comte. They both conceive an organism in which the play of functions should not cease of itself. The theory of death, says Comte, although it is founded upon that of life, is entirely distinct from it.[178]