8 FEEDS AND FEEDING 



the general term amids are compounds which the chemist calls amino 

 acids, and others which he terms true amids. In this work, unless other- 

 wise stated, amids will be used to denote both classes of substances. 



The complexity of the proteins is evident from the fact that 18 differ- 

 ent amino acids have already been identified, which may enter into their 

 composition. Just as the letters of the alphabet may be combined into 

 innumerable words, so the possibility for the combination of the amino 

 acids into different proteins is almost limitless. Thus far, scores of differ- 

 ent plant and animal proteins have been separated and examined by the 

 chemists. Some of these, such as egg albumin, contain all the known 

 amino acids, while others, as zein of corn and gliadin of wheat, lack one 

 or more of them. As will be shown later, such incomplete proteins may 

 have a lower value for animal feeding than those which are complete in 

 their composition. 



During the period of the plant's life when active growth is taking 

 place, amids are constantly being formed in the living protoplasm out of 

 the nitrates and other mineral salts and the elements composing sugar or 

 starch. These amids are continually being transported to needed points 

 and there changed into the proteins, and as a consequence do not usually 

 accumulate in the plant. Just as starch and sugar may be changed one 

 into the other in the plant, so the proteins and amids may be changed one 

 into the other as plant necessity may require. When germination starts 

 in a seed, an enzyme, or ferment, contained therein acts upon the insolu- 

 ble proteins stored in and about the germ and changes them to soluble 

 amids, so that the nitrogen may be transported to the newly forming 

 parts of the plantlet. (37) When corn forage is placed in the silo, much 

 of the protein it then contains is changed back to amids thru the fer- 

 mentations which occur. 



The life processes of both plants and animals are in general carried 

 on and maintained thru the nitrogenous or protein compounds. This 

 fact makes this class of substances of especial interest and practical 

 importance to the farmer and stockman. The active protoplasm in all 

 plant and animal cells and also the central nucleus, which controls the 

 activity of each cell, are chiefly protein in nature. In plants the 

 greater portion of the crude protein is always concentrated in the actively 

 growing portions, such as the leaves, and in the reproductive parts, such 

 as the germs of seeds. 



12. Mineral matter. It has already been pointed out in this chapter 

 that certain mineral constituents, namely, sulfur, phosphorus, potas- 

 sium, calcium, magnesium, and iron, are necessary in the formation of 

 proteins and other complex plant compounds. All these mineral constit- 

 uents are taken in solution from the soil by the roots and carried in the 

 sap to the parts of the plant where needed. Mineral matter is found 

 in small amounts thruout the plant, but the leaves contain more 

 than the other parts, due to the life processes within the leaf cells 

 and the constant evaporation of water from their surfaces by which the 



