84 The Feeding of Animals 



oxalic acid in rhubarb. Sometimes these acids are free, 

 that is, not combined with any other compound, and 

 sometimes they are united with lime or some other base, 

 forming a salt. Excepting the fruits, only fermented 

 feeding stuffs contain acids to an appreciable extent. 

 When milk sours, the sugar in it is changed to lactic acid 

 under the influence of a ferment. In silage, various 

 acids develop, the main one being lactic, accompanied 

 by acetic and other acids in much smaller proportions. 

 These are formed chiefly at the expense of the sugars 

 that enter the silo in the corn or other material which 

 is subjected to fermentation. 



ANIMAL CARBOHYDRATES 



A study of the composition of the animal body 

 teaches us that, unlike plants, it is very poor in carbo- 

 hydrate compounds. Only two carbohydrates are of 

 distinctively animal origin, viz; glycogen or animal 

 starch, and milk sugar. 



Glycogen is closely related to starch, having the same 

 percentage composition. It is a white powder, soluble 

 in water, and may be extracted in very small amounts 

 from the muscles and liver, the latter being the place 

 where it is produced. As we shall see later, it seems to 

 perform a very important office in nourishing the animal 

 body. It was formerh^ believed that another carbohy- 

 drate exists in muscle called inosite, but it is now known 

 that this substance belongs to a different class of com- 

 pounds. 



The only sugar of animal origin which is abundant 



i 



