116 THE PRINCIPLES OF AGRICULTURE. 



palmitin, and.olein. Some of them, like stearin, are 

 hard, and some, like olein, are either fluids or are easily 

 melted. 



4. Ash. The mineral parts of the animal are gener- 

 ally called the ash, because they are incombustible, or re- 

 main as ashes after burning. They are chiefly found in 

 the bones, where they are needed to give firmness and 

 hardness. They are composed chiefly of phosphate of 

 lime, carbonate of lime, phosphate of magnesium, and 

 phosphate of potassium. 



The following table will give an idea of the average 

 percentage composition of the bodies of domestic ani- 

 mals, after deducting the contents of the stomach and 

 intestines :- 



Composition of Bodies of Animals. 



Per cent. 



Water 51.9 



Nitrogenous matter 14.4 



Fat 30.3 



Ash . . 3.4 



100.0 



The Purposes of Food. The different purposes which 

 food must serve in the animal system are : 



1. To increase the Size of the Body. Mature ani- 

 mals, whose size and weight remain constant, require no 

 food for this purpose ; but in young, growing animals, 

 and those passing from a lean to a fat condition, the 

 gradual increase in weight must come from the food 

 consumed. 



The formation of animal products, like milk, must be 

 classed under this head, since the substances of which 

 milk is composed first become a part of the animal, and 

 are then converted into milk. 



