228 



Agricultural Chemistry. 



may now be used, through combustion, as a source of energy for 

 the animal body. 



When an animal is supplied with known quantities of food per 

 day, it is possible, by collecting the feces and subjecting it to the 

 same chemical analysis as was applied to the food, to determine 

 how much of each constituent of the food has been digested by 

 the animal. This applies particularly to carbohydrates, fats and 

 proteins, although not strictly accurate for these. It does not 

 apply to the mineral salts, as they are partly excreted through 

 the intestine. But by such means the digestibility of feeds is 

 measured and such results are of enormous value to the knowledge 

 of animal feeding. 



