FOOD OF ANIMALS. 195 



The principles of the food are therefore divisible into two clas- 

 ses : 



1. Supporters of nutrition, which are the albuminous matters or 

 protein compounds. 



2, Supporters of respiration — fat. 



To resume. The food of carnivorous animals is composed of, 



1. Water ; which acts only as a solvent and not as an element 

 of nutrition, and is rejected as water by the lungs and kidneys. 



2. Saline and earthy matters : they contribute to the for- 

 mation of the bones, and enter into other tissues and perform 

 other uses not understood. They correspond to the inorgmiic 

 constituents of plants. They are rejected by the urine and fceces, 

 and render these matters so valuable as manures. 



3. Albuminous matters : Protein compounds, supporters of nutri- 

 tion. These are dissolved, converted into fibrin, and constitute 

 the nutritive principle of the food. After becoming organized they 

 combine with oxygen, and are rejected as urea and carbonic acid. 

 The urea, by exposure to air, is speedily converted into carbonate 

 of ammonia.* 



4. Fat : supporter of respiration ; generator of animal heat ; 

 combines with oxygen and is rejected as carbonic acid and water. 



5. Oxygen : which is not usually called an article of food, but 

 is introduced by the lungs rather as a means of waste than of re- 

 pair, and is rejected in the combinations already mentioned. 



I pass now to the nutrition and food of herbivorous animals. 

 I The mode of nutrition in herbivorous animals differs less from 

 Ithat of carnivorous animals than a\tis formerly supposed. 



Recent chemical discoveries have established the fact that pro- 

 tein compounds, albumen, fibrin and casein, which are the sup- 

 fiorters of nutrition in carnivorous animals, also exist in vegetables 

 eady formed. Consequently herbivorous animals replace the al- 

 bumen of their blood by the albuminous matters derived from ve- 

 getables, and so far their nutritive process does not differ from that 

 jf carnivorous animals. 



The different forms of fat, oils, &c., are found in vegetable as 

 ivell as in animal food, and herein herbivorous animals are nour- 



I •Gelatine is a nitrogenized principle but not a compound of protein, which is found 

 Q the bones and cellular tissues of animals. The mode in which it is disposed of, and 

 s nutritive properties are involved in so much doubt, that I have thought it best to 

 void the question in this papers 



