360 PHYSIOLOGICAL CHEMISTRY. 



to the following equation: C 6 H 5 COOH + NH 2 .CH 2 .COOH = 

 C 6 H 5 .CO.NH.CH 2 .COOH + H 2 0. This acid may be synthetically 

 prepared from benzamid and monochlor-acetic acid, C 6 H 5 .CO.NH 2 

 + CH 2 C1.COOH = C 6 H 6 .CO.NH.CH 2 .COOH + HC1, also in other 

 different ways. 



Hippuric acid occurs in large amounts in the urine of herbivora, 

 but only in small quantities in that of carnivora. The quantity of 

 hippuric acid eliminated in human urine on a mixed diet is usually 

 less than 1 grm. per 24 hours; as an average it is 0.7 grm. After 

 eating freely of vegetables and fruit, especially such fruit as plums, 

 the quantity may be more than 2 grms. Hippuric acid is also 

 found in the perspiration, blood, suprarenal capsule of oxen, and in 

 the ichthyosis scales. Nothing is positively known in regard to the 

 quantity of hippuric acid in the urine in disease. 



The Formation of Hippuric Acid in the organism. Benzoic acid 

 and also the substituted benzoic acids are converted into hippuric 

 acid and substituted hippuric acids within the body. Also, those 

 bodies are transformed into hippuric acid which by oxidation 

 (toluol, cinnamic acid, hydrocinnamic acid) or by reduction (quinic 

 acid) are converted into benzoic acid. The question of the origin 

 of hippuric acid is therefore connected with the question of the 

 origin of benozic acid; for the formation of the second component, 

 glycocoll, from the protein substances in the body is without ques- 

 tion. 



Hippuric acid is found in the urine of starving human beings 

 (SCHULTZEN) and dogs (SALKOWSKI), also in dog's urine after a 

 diet consisting entirely of meat (MEISSI^ER and SHEPARD, SALKOW- 

 SKI, and others). It is evident that the benzoic acid originates in 

 these cases from the proteids. Benzoic acid may indeed be pro- 

 duced outside of the body by the oxidation of the albumins; the 

 benzoic acid produced on a diet consisting entirely of meat seems 

 to be derived from the putrefaction of the proteids in the intestines. 

 Among the products of the putrefaction of albumin outside of the 

 body SALKOWSKI has found phenylpropionic acid, C 6 H 5 .CH 2 .CH 2 . 

 COOH, which is oxidized in the organism to benzoic acid and 

 eliminated as hippuric acid after combining with glycocoll. Phenyl- 

 propionic acid seems to be formed from the amidophenylpropionic 

 acid, which is prepared only from the plant proteids, and the sup- 



