224 AGRICULTURAL CHEMISTRY 



used for producing heat or is stored up in the body as 

 fat. Either an excessive or a scant amount of proteidsin 

 a human or animal ration is not desirable or economical. 

 As stated under chemical properties of proteids. Section 

 298, the proteid molecule, when broken up, forms a large 

 number of simpler bodies, as fatty acids and carbohydrate 

 radicals; hence,. it is poor economy to feed proteids in 

 excess and have part perform the functions of fats and 

 carbohydrates. Protein is present in many foods in defi- 

 cient amounts, and when such foods are used, they should 

 be combined with those rich in proteids. There are a 

 few proteids which are poisonous bodies. Some of the 

 toxins produced during disease are proteids. 



306. The Amount of Proteids in Plants varies accord- 

 ing to the kind, stage of growth, and part of the plant 

 considered. Seeds always contain the largest .amount, 

 while roots and stalks contain the least. In wheat, oats, 

 barley and rye, the amount ranges from 10 to 15 per cent., 

 while in corn, it ranges from 9 to 12 percent. Beans 

 and peas contain about 25 per cent. Clover hay contains 

 from 1 1 to 14 per cent, ; timothy hay and corn fodder, 

 6 to 9 per cent. .; while in straw there is usually less than 

 4 per cent. During the early stages of growth, the dry 

 matter in all plants is relatively richer in proteids than at 

 maturity. This is because the proteids are formed mainly 

 in the early stages, while the carbohydrates are produced 

 more abundantly in the later stages of growth. 



307. Crude Protein. This term is applied to the nitroge- 

 nous compounds of foods, taken collectively, as a group. 

 The word crude is used to distinguish this group because 



