684 URINE. 



acid, hydrocinnamic acid) or by reduction (quinic acid) are converted 

 into benzoic acid. The question of the origin of hippuric acid is there- 

 tore connected with the question of the origin of benzoic acid; the for- 

 mation of the second component, glycocoll, from the protein substances 

 in the body is unquestionable. 



Hippuric acid is found in the urine of starving dogs (SALKOWSKI), 

 also in dog's urine after a diet consisting entirely of meat (MEISSNER 

 and SHEPHERD, SALKOWSKI, and others l ) . It is evident that the benzoic 

 acid originates in these cases from the proteins, and it is generally admitted 

 that it is produced by the putrefaction of proteins in the intestine. Among 

 the products of the putrefaction of protein outside of the body SALKOWSKI 

 found phenylpropionic acid, C 6 H 5 .CH 2 .CH2.COOH, which is oxidized 

 in the organism to benzoic acid and eliminated as hippuric acid after 

 combining with glycocoll. Phenylpropionic acid seems to be formed 

 from the aminophenylpropionic acid (phenylalanine), which is derived 

 from several protein substances. The supposition that the phenyl- 

 propionic acid is produced from tyrosine by putrefaction of the intestine 

 has not been substantiated by the researches of BAUMANN, SCHOTTEN, 

 and BAAS. 2 The importance of putrefaction in the intestine in pro- 

 ducing hippuric acid is evident from the fact that after thoroughly disin- 

 fecting the intestine of dogs with calomel the hippuric acid disappears 

 from the urine (BAUMANN 3 ) . 



The large quantity of hippuric acid present in the urine of herbivora 

 is partly explained by the specially active processes of putrefaction going 

 on in the intestine of these animals. According to VASiLiu 4 this can 

 hardly be correct, because, as he has found by feeding sheep with casein, 

 this would require a too intense putrefaction of the protein (indeed 40 

 per cent of it). This author's explanation lies in part that in the her- 

 bivora only a small part of the phenylalanine is burnt, and is used to a 

 greater extent in the formation of hippuric acid than in man and car- 

 nivora, and in part by the fact that the food of herbivora contains 

 larger quantities of a non-nitrogenous mother substance of the 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, 

 originates in part from the aromatic substances, e.g., quinic acid. 



The view proposed by W EISS an d others that a parallelism exists between 

 the excretion of hippuric acid and uric acid in that an increase in the first is 



1 Salkowski, Ber. d. deutsch. chem. Gesellsch., 11; Meissner and Shepard, Unter- 

 such. iiber das Entstehen der Hippursaure im thierischen Organismus. Hanover, 1866. 



2 E. and H. Salkowski, Ber. d. deutsch. chem. Gesellsch., 12; Baumann, Zeitschr. 

 f. physiol. Chem., 7; Schotten, ibid., 8; Baas, ibid., 11. 



3 Ibid., 10, 131. 



4 Vasiliu, Mitt. d. landwirt. Inst. Breslau, Bd. 4, 1907. 



