SODIUM SULPHATE 137 



crease the fluidity of the ingesta and aid in the expulsion of 

 feces. Peristaltic action is also excited through increase of 

 the mass of intestinal contents. 



Concentrated (hypertonic) solutions of the saline pur- 

 gatives withdraw water from the blood vessels of the bowels 

 because the solution in the intestines has a greater osmotic 

 pressure than the blood. When the solution in the bowel be- 

 comes sujfficiently diluted to be isotonic with the blood some 

 absorption and diuresis occurs ("salt action," see p. 140). 



The blood and urine first become concentrated, and thirst 

 is induced by the action of the saline purgatives in both with- 

 drawing water from the blood and in preventing absorption 

 of water from the food. 



Later diuresis may take place, especially when absorp- 

 tion of the saline occurs through failure of purgation. 



The basic ion, or kation, of some salts is less absorbable 

 than that of others (as Mg), and when such a basic ion is 

 combined with an acid ion of, slow absorption (as in Mg 

 SO4) the purgative effect is naturally at its maximum. 



Any cholagogue action, formerly attributed to the saline 

 purgatives, has been proved to be wanting. The saline cath- 

 artics are sometimes called hydragogues. 



Sodium sulphate is not used much in human practice 

 on account of its nauseating taste and it is said to produce 

 more griping. For the larger animals it is sometimes pre- 

 ferred to the magnesium salt in veterinary medicine. Sodium 

 sulphate is the principal ingredient of Carlsbad salts, which 

 have recently come into vogue with veterinarians, although 

 long valued in human . medicine. The formula for the arti- 

 ficial Carlsbad salts (Sal caroUnum factitium), which is the 

 preparation commonly used, is as follows: 



|B Sodii sulphatis exsiccati 40.0 



Sodii bicarbonatis 35.0 



Sodii chloridi 15.0 



Potassii sulphatis 2.0 



M. et fiat pulvis. 

 Sig. One to two heaping tablespoonfula on the food 

 two or three times daily for horses. 



Sodium sulphate is thus given as Carlsbad salts or 

 alone in small doses as a laxative, but in constipation asso- 

 ciated with indigestion and malnutrition, gentian, powdered 

 rhubarb, iron and other stomachics and tonics are often 

 combined ; while, in fever, small doses of Glauber's salts are 



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