116 THE riUNCIPLES OF AGRICULTURE. 



palmitin, and olcin. Some of thorn, like stearin, are 

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

 melted. 



4. ^4.s7/. — The mineral parts of the animal are gener- 

 ally called the asli,l)eeause they are incombiistil^le, or re- 

 main as ashes after burning. They are chiefly found in 

 the bones, whei'e they are needed to give firnmess and 

 hardness. They are comi)osed chiefly of ])hosphate of 

 lime, carbonate of lime, phosphate of magnesium, and 

 phosphate of potassiimi. 



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 j^irposes which 

 food must serve in the animal system are: — 



1. To increase the Size of t lie Body. — Matnre ani- 

 mals, whose size and weight remain constant, requii'c no 

 food for this jnirpose ; l)ut in young, growing animals, 

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

 gradual increase in weight must come fi-oin the food 

 consumed. 



The formation of animal products, like milk, must be 

 classed under this head, since the substances of which 

 milk is com])osed first become a part of the animal, and 

 are then converted into milk. 



