14 NUTRITION OF FARM ANIMALS 



the oil seeds it is replaced by oil. It is not found in the animal 

 body. 



Starch occurs in plants in the form of microscopic granules, 

 which have a peculiar form for each species, so that we may speak 

 of the starches rather than of starch. These grains consist of 

 a surrounding envelope consisting of a variety of cellulose in- 

 closing a more soluble substance or substances known as granu- 

 lose. When treated with much hot water the starch grain swells 

 and bursts the envelope and the enclosed granulose dissolves, 

 probably after undergoing more or less hydration. 



Starch may be hydrolyzed readily by dilute acids or alkalies 

 or by heat. The final product of its hydrolysis is dextrose, 

 which in an impure form constitutes commercial glucose or 

 starch sugar. Starch is therefore a dextran. As already noted, 

 certain enzyms, notably those formed in germinating seeds 

 and others secreted in the digestive tract of animals, act upon 

 starch readily with the production of maltose. Starch is also 

 acted upon by some species of bacteria with the formation of 

 lactic, butyric and other acids, methan and in some cases hy- 

 drogen. 



22. Galactans. Galactans occur more particularly in le- 

 guminous plants, other feeding stuffs being comparatively free 

 from them. 



23. Inulin. The roots of the artichoke, dahlia, dandelion, 

 chicory and other composites contain instead of starch a quite 

 similar carbohydrate, inulin, which on hydrolysis yields levulose 

 instead of dextrose, i.e., it is a levulan, 



24. The dextrins. In the hydrolysis of starch a series of 

 ill-defined, intermediate compounds is produced, collectively 

 called dextrins. Commercial dextrin is made by heating moist 

 starch to about 235 Fahrenheit. It is likewise produced in the 

 cooking of starchy materials, the brown crust of bread, for 

 example, consisting largely of dextrin. Various dextrins have 

 been separated and described, but it seems questionable 

 whether the investigators have worked with definite chemical 

 individuals. For the present, it seems wiser to speak collec- 

 tively of the dextrins as intermediate products between starch 

 and the simpler di- and mono-saccharids. 



25. Glycogen. In the liver and muscles of animals, and to 

 a less degree in other parts of the body, there is found in rather 



