CHEMIC COMPOSITION OF THE HUMAN BODY. 21 



at about 200 gm. Sodium chlorid is of much importance in the body as it 

 determines and regulates to a large extent the phenomena of diffusion 

 which are there constantly taking place. The ingested water is absorbed 

 into the blood largely in consequence of the percentage of this salt which it 

 contains. The normal percentage of sodium chlorid in the blood-plasma 

 assists in maintaining the shape and structure of the red blood-corpuscles 

 by determining the amount of water entering into their composition. The 

 same is true of other tissue elements. 



Sodium chlorid also influences favorably the general nutritive process, 

 though the manner in which it acts is not very clear. During its existence 

 in the body it undergoes chemic transformations or decompositions, yielding 

 its chlorin to form the potassium chlorid of the blood-corpuscles and muscles 

 and to form the hydrochloric acid of the gastric juice. 



Sodium phosphate, Na 2 HPO 4 , is found in all solids and fluids of the 

 body, to which, with but few exceptions, it imparts an alkaline reaction. 

 This is especially true of blood, lymph, and tissue fluids generally. It is 

 essential to physiologic action that all tissue elements should be bathed by 

 an alkaline medium. 



Sodium carbonate, Na 2 CO 3 , is generally found in association with the 

 preceding salt. As it is an alkaline compound, it also assists in giving to 

 the blood and lymph their characteristic alkalinity. In carnivorous animals 

 the sodium phosphate is the more abundant, while in the herbivorous animals 

 the sodium carbonate is the more abundant. 



Sodium sulphate, Na 2 SO 4 , is present in many of the tissues and fluids, 

 especially in the urine. Though introduced in the food, it is also, 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, however, in the 

 tissue elements, especially in the muscle tissue, nerve tissue, and red cor- 

 puscles. 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 so- 

 dium 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 preceding 

 salt. 

 MAGNESIUM COMPOUNDS. 



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

 tion with calcium phosphate, though in much smaller quantity. 



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



IRON COMPOUNDS. 



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

 ever, are also found in lymph,, bile, gastric juice, and in the pigment of the 



