208 Agricultural Chemistry. 



action of the proteolytic enzymes of the alimentary canal. They 

 niv water-soluble bodies. 



All of these protein bodies contain very similar amounts of 

 nitrogen namely, 15 to 18 per cent. Besides the above nitro- 

 genous materials constituting tissue, the animal juices contain a 

 variety of nitrogenous substances such as creatin, creatinin, sar- 

 cosine, etc., but with which we are not concerned. 



The amino-acids are simple nitrogenous bodies formed during 

 the process of digestion from the proteins of the food and are 

 believed to be the building materials out of which the animal 

 reconstructs its own tissue protein. 



The amides, principally represented by urea in the urine, are 

 the simple nitrogenous waste products of the tissues. In the 

 cow, 85 to 95 per cent of the total nitrogen in the urine is in this 

 form. 



The fats occurring in the animal body are principally stearin, 

 palmitin and olein. Stearin predominates in hard fats and olein 

 in more fluid fats. They are identical in composition with these 

 same materials described in the chapter on the plant. Lecithin, 

 a complex fat containing both nitrogen and phosphorus, is also 

 widely distributed in animal tissue. 



Carbohydrates. The important carbohydrate of the animal 

 body is glycogen. found in considerable quantities in the liver 

 and in smaller amounts in the muscular tissue. It resembles 

 starch in its constitution. At no time does it constitute an ap- 

 preciable proportion of the animal's weight. In this respect 

 animals differ from plants. In the latter the stored reserve ma- 

 terial is usually starch, while in the animal, fat is the reserve 

 material. The glycogen found in animal tissue has had its origin 

 from the various carbohydrates of the feed. These have been 

 absorbed from the digestive tract largely in the form of dextrose, 

 one of the simpler sugars, and from which glycogen has been 

 rebuilt. 



Composition of farm animals. The amounts of water, nitro- 

 genous matter, fat and ash constituents present in a large num- 



