FOOD OF ANIMALS. 197 



of nutrition with a small portion of the supporter of respiration. 

 The food of herbivorous animals is made up of a small portion of 

 the albuminous principle or supporter of nutrition, and of a much 

 larger portion of the oleaginous and saccharine principles which 

 are supporters of respiration. There is a corresponding difference 

 in the nutrition of the two classes. In carnivorous animals the 

 change of the tissues take place with rapidity, and a large supply 

 of albumen is required to take the place of that which disappears 

 in the formation of the tissues. There is sufficient carbon thus libe- 

 rated to saturate the oxygen introduced by respiration, and to main- 

 tain the animal temperature ; the small portion of fat in the food 

 saturates any surplus of oxygen. In herbivorous animals the change 

 in the tissues is slower ; less albumen is therefore required, and 

 more of the non-nitrogenized principles or supporters of respira- 

 tion are required to saturate the oxygen introduced by the lungs. 



The supporters of nutrition in food are, the protein compounds 

 albumen, fibrin and casein, as found in vegetables and animals. 

 'J'hey are destined to repair the waste of the tissues, and by their 

 decomposition give rise to carbonic acid, W'ater and urea, which, 

 by the addition of water, becomes carbonate of ammonia. 



The supporters of respiration are the different kinds of animal 

 ,and vegetable fat and oil, constituting the oleaginous principle 

 and the neutral non-nitrogenized compounds, sugar, gum, starch, 

 constituting the saccharine principle. These principles are either 

 istored up as fat, or consumed by oxygen, and in both cases are 

 ultimately thrown off in the form of carbonic acid and water. 



The organic matters of the food are then ultimately thrown off 

 in the form of water, carbonic acid and carbonate of ammonia. 

 The saline matters pass off in the urine and foeces in the form in 

 which they are introduced. 



Thus the animal restores to the atmosphere by the lungs, and 

 to the soil by the urine and foeces the compounds which serve as 

 food for plants. 



Vegetables convert inorganic compounds into proximate princi- 

 ples ; animals convert these proximate principles into inorganic 

 compounds. 



There is but one substance produced in nature which contains 

 ill the elements of the food of animals so mixed as to be capable 

 jf serving permanently as an an article of food. That is milk. 



