132 DAIRY CHEMISTRY 



cellulose. The two classes of compounds, nitroge- 

 nous and non-nitrogenous, serve different functional 

 purposes in the body. The nitrogenous compounds, 

 or proteids, are the more expensive and are present 

 in much smaller amounts than the non-nitrogenous 

 compounds. Starch, sugar, fiber or cellulose, and 

 allied bodies, are spoken of collectively as the car- 

 bohydrates, and in connection with feeding stuffs 

 only, the three general terms, " crude protein," " car- 

 bohydrates," and " crude fat " or " ether extract," are 

 employed. Food stuffs are composed of a great many 

 other compounds besides these general classes. 



124. Dry Matter. When a substance is dried at 

 a temperature of 212 F., all of the water is removed, 

 and what is left is called dry matter. All food stuffs 

 contain some water. Grains and mill products con- 

 tain from 10 to 15 per cent of water, dry hay from 12 

 to 18 per cent, and roots and tubers from 75 to 90 

 per cent. Some green crops and vegetables contain 

 as high as 95 per cent of water. The dry matter of 

 a food is simply a mechanical mixture of the differ- 

 ent compounds of which the material is composed, 

 as ash or mineral matter, crude protein, and non- 

 nitrogenous compounds, including carbohydrates and 

 crude fats. 



125. Ash. When the dry matter of a food is 

 burned at the lowest temperature necessary for 

 complete combustion, the ash or mineral matter is 

 obtained. In most agricultural plants the ash is less 

 than 10 per cent of the dry matter, and in the grain 



