DEUGS ACTING ON THE UEINAEY ORGANS 55 



"behind. In the case of the herbivora the urine is alkaline, 

 because there are larger quantities of magnesium and 

 calcium salts in the food, which precipitate phosphoric acid 

 in the stomach, and because there is an excess of alkaline 

 sodium and potassium salts in the blood. The urine may- 

 best be made acid by benzoic acid, which is converted into 

 hippuric acid during its passage through the kidneys. Sali- 

 cylic acid, urotropin, the mineral acids (as acid salts), and 

 large quantities of the vegetable acids and boric acid tend to 

 acidify the urine in a less degree. An acid urine may be 

 made alkaline by alkalies, as salts of potassium, lithium, sod- 

 ium and calcium, together with the vegetable salts, tartrates, 

 citrates and acetates, which circulate as carbonates in the 

 blood. Drugs promoting diuresis make the urine less acid 

 because the basic sodium phosphate in the blood is not so 

 readily broken up in the kidney when it diffuses through the 

 cells in great dilution. Ammonia fails to make the urine 

 alkaline because it is transformed into urea. 



Uses. — Benzoic acid is sometimes of benefit in acidify- 

 ing and disinfecting an alkaline decomposing urine of pyelitis 

 or cystitis. Recently urotropin has been used more success- 

 fully for these purposes. The alkalies are thought to be useful 

 in alkalizing the blood in certain disorders (rheumatism), 

 ' hajmoglobingemia, etc.), and the urine of carnivora, to prevent 

 the precipitation of uric acid in the urine or to aid its solu- 

 tion when already precipitated. 



DEtTGS IfLUENCING THE COMPOSITION OF TJeINB. 



Drugs contracting efferent vessels of the Malpighian 

 bodies diminish the flow of blood and urea-excretion and 

 increase the elimination of water; while those dilating the 

 afferent vessels cause more blood to pass through the kidney 

 and promote the secretion of solids and water. Drugs 

 stimulating the cells of the convoluted tubes augment 

 especially the urinary solids. The composition of the urine 



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