The Animal Body. 213 



varies from 40 to 60 per cent. No definite percentage can be 

 given, as the amount, up to a certain limit, will vary with the 

 supply of lime and phosphoric acid in the food and also with 

 the source of the bone. 



The ash of bone is not entirely phosphate of lime, but contains 

 in addition carbonates, fluorides, chlorides and magnesia. The 

 following analysis of bone ash is given by Ingle : 



Calcium phosphate 86 . per cent 



Magnesium phosphate 1.0 " 



Calcium, as carbonate, chloride and fluoride. .. 7.3 " . 



Carbon dioxide 6.2 " 



Chlorine 0.2 



Fluorine 0.3 " 



Muscular tissue consists largely of proteins and water, but 

 contains in addition small quantities of fat, glycogen (animal 

 starch), and certain nitrogenous extractives, such as creatin, 

 ereatinin, xanthin and guanin. Small quantities of dextrose are 

 also contained in muscle tissue. The ash of muscle consists 

 Largely of potash and phosphoric acid compounds, but there are 

 also present small amounts of sodium, magnesium, calcium, chlo- 

 rine and iron. Muscle usually contains about 75 to 80 per cent 

 of water, and 20 to 25 per cent of solids. 



"When a muscle does work, the glycogen and sugar are burned 

 at an increased rate and the blood, which bathes the muscle, re- 

 ceives an increased proportion of carbon dioxide. Fats are also 

 sources of mechanical work for the muscle. When fats and 

 carbohydrates are available for consumption, the nitrogenous 

 waste of the muscle is not increased by exercise, and only the 

 normal amount of waste nitrogenous products, as urea, uric acid, 

 etc., appear as the result of the life processes. 



Fatty tissue is made up of relatively large, oval, or spherical 

 cells. These cells consist of a nitrogenous membrane, filled with 

 fat, which during life is fluid. The fats, which resemble in con- 

 stitution the vegetable oils already described, are chiefly com- 

 posed of stearin, palmitin and olein. The fat cells may be 



