CHAPTER H 



COMPOSITION OF THE ANIMAL BODY DIGESTION- 

 METABOLISM 



I. COMPOSITION OF THE ANIMAL BODY 



In gaining a knowledge of the feeding of live stock it is necessary 

 to understand clearly of what substances the bodies of farm animals are 

 composed. In the preceding chapter we have studied the composition of 

 plants and the manner in which the plant compounds are formed. Let 

 us now consider the nature and composition of the bodies of farm 

 animals, which are built up and nourished by plants. 



28. The animal body. The unit of the animal body is the life-holding 

 cell, which, associated with myriads of others and modified in innumer- 

 able ways, makes up the body structure. In studying the higher animals 

 we may regard their bodies as consisting of a bony skeleton surrounded 

 by an elaborate muscular system. Fatty tissue permeates the bones and 

 muscles, filling in and rounding out the body form, and around all is the 

 enveloping skin. Within the body cavity are the various special organs, 

 such as the heart, stomach, etc., designed for dissolving, assorting, dis- 

 tributing and utilizing the nutritive material of the food and for con- 

 veying and disposing of the waste. 



Protein makes up a much larger part of the dry matter in the bodies 

 of animals than in plants. Contrasted with plant cells, in which the 

 cell wall is made of cellulose, the cell wall or membrane in animals is 

 protein. The muscles, which make possible the movements of the body, 

 the nerves and brain, which control and direct all body activities, and 

 also the various internal organs are chiefly composed of protein. Pro- 

 tein also makes up the cartilages in the body, the network of connect- 

 ive tissue thruout the muscles and organs, and such epidermal or outer 

 tissues as the skin, hair, wool, feathers, hoofs, nails, and horns. The 

 bones also contain considerable protein. About two-thirds of the weight 

 of dry bones from which the fat has been extracted consists of mineral 

 matter, which gives them their hardness and density, and the remainder 

 of protein, which makes them elastic and tenacious. By soaking a fresh 

 bone in weak hydrochloric acid the mineral matter may be dissolved 

 out, leaving the protein and other organic parts. While the original 

 shape of the bone will be retained, the mass, which consists chiefly of 

 protein, will be soft and flexible, like India rubber. 



Fats form the chief part of the fatty or adipose tissues of the body 

 and are also distributed in smaller amounts thruout most other parts. 

 The animal body stores nearly all its reserve food in the form of fat, 



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