The most remarkable property of the gastric juice is unquestionably the power which it possesses of dissolving and reducing to the appearance of a soft thickish fluid mass every thing in the shape of food which is submitted to its action,--while it exerts no perceptible influence on living or inorganic matter; for, so far as is yet known, nothing which is not organized, or which is still alive, can serve as nutriment for the animal frame. Water is the only inorganic body which is taken into the system for its own sake, and all mineral and other inorganic productions enter it as component parts of previously organized substances of either an animal or a vegetable nature. To a great extent, indeed, vegetation seems to be merely a process for the conversion of inorganic matter into a proper nutriment for the support of animal life; and many species of animals seem in their turn to be little else than living machines for the conversion of vegetable substances into a nutriment fit for other species by which they are intended to be devoured. It is true that, in some parts of South America, the natives, pressed by want, consume quantities of a soft unctuous clay, which is of course destitute of organization; but as there is every reason to believe that no nourishment is derived from it, and that it merely serves to allay the pangs of hunger, such instances form no exception to the general rule. It would have been easy for the Creator to bestow such a structure on all animals, as to make them subsist entirely on vegetable aliment. But the arrangement which He has seen fit to adopt, is the source of an infinitely greater amount of active enjoyment than what could otherwise have existed. Had there been no beasts of prey, the world would soon have been overrun with herbivorous creatures to such an extent, that their numbers would speedily have become excessive in reference to the possible supply of food, and there would have been infinitely more suffering from starvation and disease, than what actually arises out of their existing relation to each other. On the present plan, there is ample food and enjoyment for all; and when the time does arrive when one animal must become the prey of another, the deprivation of life is in most cases unforeseen, and the suffering which attends it is in general only momentary in duration. There is thus both complete enjoyment of life while it lasts, and a great additional field opened for the support of an immense class of animals, which, with their present constitution, could not otherwise have existed at all.[26]