HUMAN PHYSIOLOGY. 



Though insoluble, it is held in solution by the carbonic acid diffused 

 through the fluids. 



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



SODIUM COMPOUNDS. 



Sodium chloiid, 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 impor- 

 tance in the body, as it determines and regulates to a large extent 

 the phenomena of diffusion which are there constantly taking place. 

 This is illustrated by the fact that a solution of albumin placed in 

 the rectum without the addition of this salt will not be absorbed. 

 When the salt is added, absorption takes 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 the general nutritive process, in- 

 creasing the disintegration of the proteids, as shown by the increased 

 amount of urea excreted. During its existence in the body it under- 

 goes some chemic transformations or decompositions, yielding its 

 chlorid to form 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 also an alkaline compound, it 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 reverse is true. 



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

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



