CHEMIC COMPOSITION OF THE HUMAN BODY. 27 



in all probability, formed in the body from the decomposition and 

 oxidation of the proteids. 



POTASSIUM COMPOUNDS. 



Potassium chlorid, KC1, is met with in association with sodium 

 chlorid in almost all situations in the body. It preponderates, how- 

 ever, in the tissue elements, especially in the muscle tissue, nerve 

 tissue, and red corpuscles. The plasma- with which these structures 

 are bathed contains but a very small amount of this salt, but, as 

 previously stated, a relatively large quantity of sodium chlorid. 

 Though introduced to some extent in the food, it is very likely that 

 it is also formed through the decomposition of the sodium chlorid. 



Potassium phosphate, K 2 HPO 4 , is found in association with sodium 

 phosphate in all the fluids and solids. As it has similar chemic 

 properties, its functions are practically the same. 



Potassium carbonate, K 2 CO 3 , is generally found with the preced- 

 ing salt. 



MAGNESIUM COMPOUNDS. 



Magnesium phosphate, Mg 3 (PO 4 ) 2 , is found in all tissues, in asso- 

 ciation with calcium phosphate, though in much smaller quantity. 



Magnesium carbonate, MgCO 3 , occurs only in traces in the blood. 

 Both of these compounds have functions similar to the calcium 

 compounds, and exist, in all probability, under similar conditions. 



IRON COMPOUNDS. 



Iron is a constituent of the coloring matter of the blood. Traces, 

 however, are also found in lymph, bile, gastric juice, and in the 

 pigment of the eyes, skin, and hair. The amount of iron contained 

 in a body weighing seventy-five kilogram^ is about three gm. It 

 exists under various forms e. g,, ferric oxid, ferrous oxid, and in 

 combination with organic compounds. 



Chemic analysis thus shows that the chemic elements into which 

 the compounds may be resolved by an ultimate analysis do not exist 

 in the body in a free state, but only in combination, and in charac- 

 teristic proportions, to form compounds whose properties are the 

 resultant of those of the elements. Of the four principal elements 

 which make up ninety-seven per cent, of the body, O, H, N are 

 extremely mobile, elastic, and possessed of great atomic heat. C, H, 



