MINERAL SUBSTANCES 55 



taking place; but the greater portion of the excess of 

 heat appears to be utilized by its becoming converted 

 into motion; for we find that after rapid movement, 

 which is necessarily accompanied by considerable waste 

 of tissue, there is but a very slight increase in the 

 temperature of the body. This is in accordance with the 

 fact that heat and motion are but modifications, though 

 under different forms, of force. 



Mineral Substances. — These, with the exception of 

 common salt, are obtained in ample sufficiency from the 

 various grasses. Corn contains them in a far smaller 

 proportion (see p. 50) : hence the necessity of the former 

 food. We may observe, as before remarked, that bran 

 contains a large proportion of phosphorus, which is an 

 indispensable factor in all the functions of life. 



The phosphates of lime and magnesia, the carbonate 

 of lime, and silica are the chief agents that give solidity 

 to the bony skeleton. The phosphate and carbonate of 

 soda "would seem to have as their chief purpose the 

 maintenance of the alkalinity of the blood, on which 

 depends not merely the solubility of its albumen, but the 

 facility of its passage through the capillaries, and the 

 readiness with which its combustive materials are oxidized, 

 whilst they also increase the absorptive power of the 

 serum for gases, and thus play an important part in the 

 respiratory process. The salts of potash appear to be 

 specially required for the nutrition of the muscles and 

 nerves, since they are largely present in the fluids and 

 ashes of these tissues, but they probably exert the same 

 general influence as those of soda. . . . The presence of 

 the earthy salts, on the other hand, would seem to have 



