its help. Moreover, mechanical adaptation to the medium becomes a matter of more difficulty as we ascend in the scale of beings; and from this arise many anomalies. Individuals retain tastes which were formerly favorable, but are now useless or injurious, as the passion for hunting and the warlike disposition, which are, according to Mr. Spencer, relics of savage instincts. Other anomalies arise in consequence of an antagonism between the individual and the species, as when the lower animals destroy themselves by division to make new beings, and some of a higher grade die immediately after performing the act of reproduction. Mechanical selection is likewise incompetent to give an explanation of the origin of pleasure and pain, and to throw light on their primitive connection with life. We believe that there is a close and strong bond between these affections of life, independent of natural selection, which modifies and perfects the connection, but does not create it, and that we can find the' reason of this connection by inquiring of physiology and psychology.
Let us inquire, first, what physiology can teach us about it. In previous investigations in this direction we have reasoned too much from complex organisms already developed. The thing we ought to learn is what, in a cell or a nerve, arouses the rudiment of pleasure or of pain, to be extended ultimately to the whole of the living body. The nervous elements are constantly the scene of a double chemical labor; a "negative" work of reparation, consisting in the formation of very complex albuminoid compounds; and a "positive" one of expenditure, consisting in the reduction of these compounds to more simple ones. In the state of repose, these two molecular labors are performed simultaneously, and are nearly in equilibrium. In that case we are conscious simply of a condition of vital calm and evenness, with which is connected a vague feeling of rest and comfort. An external agent, a sound, a light, or a shock, comes to excite a nerve; the interruption of the equilibrium produces a movement of nervous expenditure, and this excites a simultaneous movement of reparation—just as water flowing out of a siphon-tube calls up into its place water which rises. These two labors are equally necessary to life, and must be suitably proportioned to one another for life to subsist. Nervous reparation, which accumulates force, always has for its result and object exercise, which expends force. In natural selection, the animal can not be satisfied with repairing his nervous system; he must put it to use, to seek food and defend himself; he must expend, to preserve. This being so, can we assume, as Léon Dumont does ("Théorie scientifique de la sensibilité"), that the accumulation of force, its "storage in the nerve," is the only cause of pleasure? Every nervous action, says this author, is an expenditure of force. How can expenditure, which is a loss, produce pleasure, the cause of which, on the other hand, is sought in augmentation of force? This view arises from an imperfect conception of the relation of the two molecular labors. The
