FEEDING FOR SPECIAL PURPOSES. 121 



furnish the animal with the materials of which the bony 

 skeleton of its body consists. 



"Saline substances chlorides of sodium and pota&- 

 sium, sulphate and phosphate of potash and soda, and 

 some other mineral matters occurring in food supply 

 the blood, juice of flesh, and various animal juices, with 

 the necessary mineral constituents. 



" The healthy state of an animal can thus only be pre- 

 served by a mixed food; that is, food which contains all 

 the proximate principles just noticed. Starch or sugar 

 alone cannot sustain the animal body, because neither of 

 them furnishes the materials to build up the fleshy parts 

 of the animal. When fed on substances in which an in- 

 sufficient quantity of phosphates occurs, the animal will 

 become weak, because it does not find any bone-pro- 

 ducing principles in its food. Due attention, therefore, 

 ought to be paid by the feeder to the selection of food 

 which contains all the kinds of matter required, nitro- 

 genized as well as non-nitrogenized, and mineral sub- 

 stances ; and these should be mixed together in the 

 proportion which experience points out as best for the 

 different kinds of animals, or the particular purpose for 

 which they are kept." 



"On the nutrition of cows for dairy purposes," Dr. 

 Voelcker still further observes that "milk may be re- 

 garded as a material for the manufacture of butter or 

 of cheese ; and, according to the purpose for which the 

 milk is intended to be employed, whether for the manu- 

 facture of butter or the production of cheese, the cow 

 should be differently fed. 



" Butter contains carbon, hydrogen, and oxygen, and 

 no nitrogen. Cheese, on the contrary, is rich in nitro- 

 gen. Food which contains much fatty matter, or sub- 

 stances which in the animal system are readily con- 

 verged into fat, will tend to increase the proportion of 

 11 



