

THE URINE. 



position that the phenylpropionic acid is produced from tyrosin by' 

 putrefaction in the intestines has not been substantiated by the 

 researches of BAUMANN, SCHOTTEN and BAAS. The importance 

 of putrefaction in the intestines in producing hippuric acid is evi- 

 dent from the fact that after thoroughly disinfecting the intestines 

 of dogs with calomel the hippuric acid disappears from the urine 



The large quantity of hippuric acid present in the urine of her- 

 bivora is partly explained by the fact that vegetable proteids yield 

 perhaps larger amounts of amidophenylpropionic acid, and partly 

 by the specially active processes of putrefaction going on in the 

 intestines of herbivora. These circumstances do not entirely ex- 

 plain this excess of hippuric acid (SALKOWSKI). The abundant 

 elimination of hippuric acid by herbivora may in part depend on 

 the great amount of aromatic substances in the food of these ani- 

 mals which is converted into benzoic acid. There is hardly any 

 doubt that the hippuric acid in human urine after a mixed diet, 

 and especially after a diet of vegetables and fruits, has in part a 

 similar origin. 



The kidneys may be considered in dogs as special organs for 

 the synthesis of hippuric acid (SCHMIEDEBERQ and BUNGE). In 

 other animals, as in rabbits, the formation of hippuric acid seems 

 to take place in other organs, such as the liver and muscles. The 

 synthesis of hippuric acid is therefore not exclusively limited to any 

 special organ, though perhaps in some species of animals it may be 

 more abundant in one organ than in another. 



Properties and reactions of hippuric acid. This acid crystallizes 

 in semi-transparent, milk-white, long, four-sided rhombic prisms or 

 columns, or in needles by rapid crystallization. They dissolve in 

 600 parts cold water, but more easily in hot water. They are easily 

 soluble in alcohol, but with difficulty in ether. They are more 

 easily soluble (about 12 times) in acetic ether than in ethyl ether. 

 Petroleum ether does not dissolve them. 



On heating hippuric acid it first melts to an oily liquid which 

 crystallizes on cooling. By continuing the heat it decomposes, pro- 

 ducing a red mass and a sublimate of benzoic acid, with the genera- 

 tion, first, of a peculiar pleasant odor of hay, and then an odor of 

 hydrocyanic acid. Hippuric acid is easily differentiated from ben- 



