Animals, after they have been expanded in, and brought out of, the wombs that are suitable to the elements of their machine, enlarge, strengthen, acquire new properties, new energies, new faculties; either by deriving nourishment from plants analogous to their being, or by devouring other animals whose substance is suitable to their preservation; that is to say, to repair the continual deperdition or loss of some portion of their own substance, that is disengaging itself every instant. These same animals are nourished, preserved, strengthened, and enlarged, by the aid of air, water, earth, and fire. Deprived of air, or of the fluid that surrounds them, that presses on them, that penetrates them, that gives them their elasticity, they presently cease to live. Water, combined with this air, enters into their whole mechanism of which it facilitates the motion. Earth serves them for a basis, by giving solidity to their texture: it is conveyed by air and water, which carry it to those parts of the body with which it can combine. Fire itself, disguised and enveloped under an infinity of forms, continually received into the animal, procures him heat, continues him in life, renders him capable of exercising his functions. The aliments, charged with these various principles, entering into the stomach, re-establish the nervous system, and restore, by their activity, and the elements which compose them, the machine which begins to languish, to be depressed, by the loss it has sustained. Forthwith the animal experiences a change in his whole system; he has more energy, more activity; he feels more courage; displays more gaiety; he acts, he moves, he thinks, after a different manner; all his faculties are exercised with more ease. This igneous matter, so congenial to generation--so restorative in its effect--so necessary to life, was the JUPITER of the ancients: from all that has preceded, it is clear, that what are called the elements, or primitive parts of matter, variously combined, are, by the agency of motion, continually united to, and assimilated with, the substance of animals--that they visibly modify their being--have an evident influence over their actions, that is to say, upon the motion they undergo, whether visible or concealed.