Note 250 — Chapter I

Darwinism explains adaptation only as the result of the struggle for existence, and of selection which is a form of this struggle. In one individual a quality appears accidentally, which makes it more capable of preserving itself and of conquering its enemies than those individuals not born with this quality. It finds more favourable conditions of existence, leaves behind it more numerous descendants inheriting this advantageous quality, and by the survival of the fittest and the disappearance of the less fit, the whole species comes into the possession of this advantageous quality. I do not at all deny that an accidental individual deviation from the type of the species, which proves an advantage in the struggle for existence, can be a source of transformations having as their result a better adaptation of the species to given and unmodifiable circumstances. But I do not believe that such an accident is the only source, or even the most frequent source, of such transformations. The process of adaptation appears to me to be quite otherwise, viz., the living being experiences in some situation feelings of discomfort from which he wishes to escape, either by change of situation (movement, flight), or by trying to act vigorously on the causes of these feelings of discomfort (attack, modification of natural conditions). If the organs possessed by the living being, and the aptitude these organs have acquired, are not sufficient to furnish the counteractions felt and wished for as necessary to those feelings of discomfort, the weaker creatures submit to their destiny, and suffer or even perish. More vigorous individuals, on the contrary, make violent and continuous efforts in order to attain their design, of flight, defence, attack, suppression of natural obstacles; they give strong nervous impulses to their organs to increase to the highest degree their functional capacity, and these nervous impulses are the immediate cause of transformations, giving to the organs new qualities, and rendering them more fit to make the living creature thrive. That the nervous impulse produces, as a consequence, an increase in the flow of blood, and a better nutrition for the organ in play, is a positive biological fact. In my opinion, then, adaptation is most frequently an act of the will, and not the result of qualities accidentally acquired. It has as premise the clear perception and representation of the external causes of the feelings of discomfort, and a keen desire to escape from them, or, again, that of procuring feelings of pleasure, i.e., an inorganic appetite. Its mechanism consists in the elaboration of an intense representation of serviceable acts of certain organs, and in the sending of adequate impulses to these organs. That such impulses can modify the anatomical structure of the organs, Kant already anticipated when he wrote his treatise, Von der Macht des Gemüthes; and modern therapeutics has fully confirmed this, by showing that the stigmata of a Louise Lateau, the healing of tumours on the tomb of the Deacon Paris, the modifications induced by suggestion on the skin of hysterical subjects, the formation of birth-marks by eventualities and emotions, are the effect of presentations on the bodily tissues. It was wrong to laugh at Lamarck for teaching that the giraffe has a long neck because it has continually stretched it in order to be able to feed off the topmost foliage of plants with tall stems. When the animal elaborates the clear idea that he ought to elongate his neck as much as possible in order to reach the elevated foliage, this presentation will influence in the strongest manner the circulation of the blood in all the tissues of the neck; these will be quite differently nourished from what they would be without this presentation, and the changes desired by the animal will certainly take place little by little, if his general organization makes them possible. Knowledge and will are therefore causes of adaptation—not the will in the mystical sense of Schopenhauer, but the will that is the dispenser of nervous impulses. This summary must suffice for the reader; this is not the place to develop it more, and to demonstrate in detail how fertile these ideas are for the theory of evolution.