966 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



of water and of urea in the urine. 1 The increase of urea means increase in 

 proteid metabolism, and is produced by all salts ; it is to be explained by the 

 increased motion of water from the cell, the same effect being seen on drinking 

 large quantities of water (see p. 948). 



Sodium sulphate, Na-jSO^ called " Glauber's salt," is found together with 

 potassium sulphate in the urine in the condition of preformed sulphuric acid 

 (see p. 951). If fed, it reappears in the urine. It acts on the epithelial cells 

 of the intestines, preventing the absorption of water, consequently causing diar- 

 rhoea. Other laxatives act in the same way. 



Sodium Phosphates. The primary (NaH 2 PO 4 ) and the secondary 

 (Na 2 HPO 4 ) salts are found to a small extent in the blood-plasma and other 

 fluids, and in the urine. As with the potassium phosphates, carbonic oxide 

 acts when in certain excess to convert the secondary phosphate into NaH 2 PO 4 

 and NaHCO 3 . These two, however, may react on one another to drive off car- 

 bonic acid (see p. 961). Carnivorous urine owes its acid reaction principally 

 to primary sodium phosphate. If a mixture of NaH 2 PO 4 and Na 2 HPO 4 be 

 permitted to diffuse through membranes, the NaH 2 PO 4 passes through in 

 greater quantity, and this process may take place in the kidney. 2 Secondary 

 sodium phosphate dissolves uric acid on warming, forming sodium acid urate 

 and primary phosphate, which solution reacts acid (Voit). Urine standing in 

 the cold precipitates uric acid with the formation of secondary phosphates, 

 while the reverse reaction with return of original acidity takes place on warm- 

 ing the urine. 



Sodium Carbonates. Of these there are two, the primary, NaHCO 3 , and 

 the neutral, Na 2 CO 3 . The organization owes its alkaline reaction, and also its 

 power of combining with carbonic acid, almost entirely to sodium carbonate. 

 Saliva, pancreatic and intestinal juice are strongly alkaline with sodium carbonate, 

 as are also blood, lymph, and other fluids. If the organization be acidified, by 

 feeding acid to a rabbit, for example, death occurs even before complete loss 

 of the blood's alkalinity, while venous injections of sodium carbonate at the 

 proper time restore the animal. Carbonic oxide cannot be removed from the 

 tissues in the acidified blood. Sodium carbonate treated with carbonic acid 

 becomes acid sodium carbonate, and this change is effected in the internal res- 

 piration, where the cells give CO 2 to the blood. Treated with acids, both car- 

 bonates liberate carbonic oxide a reaction which takes place in the blood 

 (see p. 961). Bunge suggests that the acid chyme of the stomach, into whose 

 finest particles the alkaline intestinal juice diffuses, is especially penetrable by 

 the latter's enzymes, because liberated carbonic oxide has separated the particles 

 of chyme from each other. The same principle would hold true of a morsel 

 well mixed with saliva, which, as is well known, is more easily penetrable by 

 gastric juice than one not so mixed. Sodium carbonate may be obtained for 

 the body either directly from the food by absorption, or indirectly through 



1 Voit : Op. cU. t p. 160. 



2 Soubiranski : Archiv fur exper. Pathologic und Pharmakologie, 1895, Bd. 35, p. 178. 



