The same elements, which under certain circumstances serve to nourish, to strengthen, to maintain the animal, become, under others, the principles of his weakness, the instruments of his dissolution--of his death: they work his destruction, whenever they are not in that just proportion which renders them proper to maintain his existence: thus, when water becomes too abundant in the body of the animal, it enervates him, it relaxes the fibres, and impedes the necessary action of the other elements: thus, fire admitted in excess, excites in him disorderly motion destructive of his machine: thus, air, charged with principles not analogous to his mechanism, brings upon him dangerous diseases and contagion. In fine, the aliments modified after certain modes, in the room of nourishing, destroy the animal, and conduce to his ruin: the animal is preserved no longer than these substances are analogous to his system. They ruin him when they want that just equilibrium that renders them suitable to maintain his existence. Plants that serve to nourish and restore animals are themselves nourished by earth; they expand on its bosom, enlarge and strengthen at its expense, continually receiving into their texture, by their roots and their pores, water, air, and igneous matter: water visibly reanimates them whenever their vegetation or genus of life languishes; it conveys to them those analogous principles by which they are enabled to reach perfection: air is requisite to their expansion, and furnishes them with water, earth, and the igneous matter with which it is charged. By these means they receive more or less of the inflammable matter; the different proportions of these principles, their numerous combinations, from whence result an infinity of properties, a variety of forms, constitute the various families and classes into which botanists have distributed plants: it is thus we see the cedar and the hyssop develop their growth; the one rises to the clouds, the other creep humbly on the earth. Thus, by degrees, from an acorn springs the majestic oak, accumulating, with time, its numerous branches, and overshadowing us with its foliage. Thus, a grain of corn, after having drawn its own nourishment from the juices of the earth, serves, in its turn, for the nourishment of man, into whose system it conveys the elements or principles by which it has been itself expanded, combined, and modified in such a manner, as to render this vegetable proper to assimilate and unite with the human frame; that is to say, with the fluids and solids of which it is composed.