FOOD OF CARNIVORA. 55 



excrements are nothing else than the incombustible, or 

 imperfectly burned, parts of the food. 



In the preceding pages it has been assumed, that the 

 elements of the food are converted by the oxygen ab- 

 sorbed in the lungs into oxidized products ; the carbon 

 into carbonic acid, the hydrogen into water, and the 

 nitrogen into a compound containing the same elements 

 as carbonate of ammonia. 



This is only true in appearance ; the body, no doubt, 

 after a certain time, acquires its original weight. The 

 amount of carbon, and of the other elements, is not 

 found to be increased, exactly as much carbon, hy- 

 drogen, and nitrogen has been given out as was supplied 

 in the food ; but nothing is more certain than that the 

 carbon, hydrogen, and nitrogen given out, although 

 equal in amount to what is supplied in that form, do not 

 directly proceed from the food. 



It would be utterly irrational to suppose that the 

 necessity of taking food, or the satisfying the appetite, 

 had no other object than the production of urea, uric 

 acid, carbonic acid, and other excrementitious matters, 

 of substances which the system expels, and conse- 

 quently applies to no useful purpose in the economy. 



In the adult animal, the food serves to restore the 

 waste of matter ; certain parts of its organs have lost 

 the state of vitality, have been expelled from the sub- 

 stance of the organs, and have been metamorphosed 

 into new combinations, which are amorphous and unor- 

 ganized. 



The food of the carnivora is at once converted into 



