244 THE VITAL FUNCTIONS. 



In the animal kingdom we observe these processes mul- 

 tiplied to a still greater extent; and the resulting substances 

 are even farther removed from the oriiirinal condition of un- 

 organized matter. In the first place, the food of animals, 

 instead of being simple, like that of plants, has always un- 

 dergone previous preparation; for it has either constituted 

 a portion of some otlier organized being, or it has been a 

 product of organization; in each case, therefore, partaking 

 of the complexity of composition which characterizes or- 

 ganized bodies. Still, whatever may be its qualities when 

 received into the stomach, it is soon converted by the pow- 

 ers of digestion into a milky, or transparent fluid, having 

 nearly the same uniform properties. We have seen that 

 there is scarcely any animal or vegetable substance, how- 

 ever dense its texture, or virulent its qualities, but is capa- 

 ble of affording nourishment to various species of animals. 

 Let us take as an example the elytra of cantharides, which 

 are such active stimulants when applied in powder to the 

 skin in the ordinary mode of blistering; we find that, not- 

 withstanding their highly acrid qualities, they constitute 

 the natural food of several species of insects, which devour 

 them with great avidity; and yet the fluids of these insects, 

 though derived from this pungent food, arc perfectly bland, 

 and devoid of all acrimony. Cantharides are also, accord- 

 ing to Pallas, the favourite food of the hedge-hog; although 

 to other mammalia they are highly poisonous. It has also 

 been found that even those animal secretions, (such as the 

 venom of the rattle-snake,) which, when infused, even in 

 the minutest quantity, into a wound, prove instantly fatal, 

 may be taken into the stomach without producing any de- 

 leterious effects. These, and a multitude of other well- 

 known fiicts, fully prove how completely substances re- 

 ceived as aliment may be modified, and their properties 

 changed, or even reversed, by the powers of animal diges- 

 tion. 



No less remarkable arc the transmutations, which the 

 blood itself, the result of these previous processes, is subse- 



