214 THE PRINCIPLES OF AGRICULTURE 



in the milk of the carnivorous animal when red 

 flesh only has been fed. In this case the origi- 

 nal nitrogenous food is broken up into two or 

 more chemical products, one of which contains 

 only carbon and hydrogen, or these with the 

 addition of oxygen, while all of the nitrogen 

 goes to other product or products. 



373. Mineral salts {lS2a) form a third gi'oup 

 of food principles. These are essential in repair- 

 ing the waste of tissues, and in forming secre- 

 tions like milk, bile and gastric juice. 



374. The ideal food contains all of these 

 three groups in forms which can be dissolved, 

 digested and assimilated into the animal tissues. 

 Milk is an ideal food. In it the non- nitroge- 

 nous aliments — sugar, butter -fat — are united with 

 the nitrogenous — casein, albumin, — and with the 

 salts in proportions adapted to the needs of the 

 system. 



375. A well-balanced ration for the adult 

 animal is one in which these different classes of 

 food constituents bear a somewhat definite rela- 

 tion to each other, due allowance being made for 

 the uses to which the animal is put. The grow- 

 ing, working or milking animal requires more of 

 the nitrogenous elements, while the fattening ani- 

 mal may exchange much of this for the non- 

 nitrogenous. 



376. The living body, however, is not like a 



