720 URINE. 



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 SHEPARD, SALKOWSKI, and others 1 ). 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, C6H5.CHo.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 phenylalanine. The supposition that the phenylpro- 

 pionic 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 dis- 

 infecting the intestine of dogs with calomel the hippuric acid disappears, 

 from the urine (BAUMANN S ) . 



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, orig- 

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



The view proposed by WEISS and others that a parallelism exists between 

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

 followed by a diminution in the second, and that, for example, quinic acid pro- 

 duces a diminution in the excretion of uric acid corresponding to the increased 

 formation of hippuric acid (WEISS, LEWIN), cannot be considered as sufficiently 

 proven (HupFER). 5 



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

 Untersuch. iiber das Entstehen der Hippursaure im thierschen Organismus. Hanover, 

 1886. 



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. 



6 Weiss, Zeitschr. f. physiol. Chem., 25, 27, 38; Lewin, Zeitschr. f. klin. Med., 42; 



