CHEMIC COMPOSITION OF THE HUMAN BODY 21 



sion in hydrochloric acid. Though insoluble in water, it is held in solution 

 in the blood and milk by the protein constituents, and in the urine by the 

 acid phosphate of soda. The total quantity of calcium phosphate which 

 enters into the formation of the body has been estimated at 2.5 kilograms. 

 The amount eliminated daily from the body has been estimated at 0.4 gm.> 

 a fact which indicates that nutritive changes do not take place with much 

 rapidity in those tissues in which it is contained. 



Calcium carbonate, CaCO 3 , is present in practically the same situa- 

 tions in the body as the phosphate, and plays essentially the same rdle. It 

 is, however, found in the crystalline form, aggregated in small masses in the 

 internal ear, forming the otoliths, or ear stones. Though insoluble, it is held 

 in solution by the carbonic acid diffused through the fluids. 



Calcium fluorid, CaF 2 , is found in bones and teeth. 

 SODIUM COMPOUNDS. 



Sodium chlorid, NaCl, is present in all the tissues and fluids of the 

 body, but especially in the blood, 0.6 per cent., lymph, 0.5, and pancreatic 

 juice, 0.25 per cent. The entire quantity in the body has been estimated 

 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, m 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 



