CASUAL URINARY CONSTITUENTS. 739 



does not hold good. He found that the aromatic fatty acids with straight 

 carbon chains such as phenyl butyric acid and phenyl caproic acid, are 

 changed into phenyl acetic acid, which is then conjugated with glycocolJ, 

 forming phenylaceturic acid, while the acids with uneven carbon side- 

 chains, such as phenyl propionic and phenylvalerianic acids, yield benzoic 

 acid and are eliminated as hippuric acid. This behavior is explained 

 if, as is made probable by KNOOP, in the demolition those aromatic fatty 

 acids an oxidation takes place in those groups which are in the /^-position 

 to the carboxyl group. FRIEDMANN has nevertheless raised objections 

 to this view, but DA.KIN, 1 on the other hand, has reported observations 

 which support it strongly. This author found that in the dog phenyl 

 propionic acid was eliminated as hippuric acid, and also a part as 

 phenyl-9-oxypropionic acid, C 6 H 5 .CH(OH).CH 2 COOH and acetophenone, 

 C 6 H 5 .CO.CH 3 , which presupposes an oxidation in the /9-position. As 

 the last two mentioned bodies can be converted into benzoic acid in the 

 body, DAKIN suggests that the demolition of phenylprop ionic acid at 

 least in part occurs with phenyl-/?-oxypropionic acid and acetophenone 

 as mtemediary steps, and he also undoubtedly finds that in the demolition 

 of the saturated fatty acids that the first stage is the oxidation of the 

 hydrogen combined to a carbon atom in the /^-position. KNOOP'S rule 

 does not apply to the propionic acids substituted in the a-position, i.e., 

 phenylalanine, phenyl-a-lactic acid, and phenyl-a-ketopropionic acid r 

 which, like tyrosine and a-amino-cinnamic acid, are burnt in the body. 

 SCHOTTEN'S rule, according to which all acids having three carbon atoms 

 in the side chain of which the middle one has a NH 2 group attached, are 

 almost completely burnt in the organism, has been extended by these 

 exceptions. 



If several side chains are present in the benzene nucleus, then only one 

 is always oxidized into carboxyl. Thus xylene, C6H 4 (CH 3 ) 2 , is oxidized 

 into toluic acid, CoH 4 (CH 3 )COOH (SCHULTZEN and NAUNYN) ; mesitylene, 

 C b H 3 (CH 3 ) 3 , into mesitylenic acid, C 6 H 3 (CH 3 ) 2 .COOH (L. NENCKI); 

 cymene, (CH 3 )2CH.C 6 H 4 .CH 3 , into cumic acid (M. NENCKI and ZiEGLER 2 ) ; 



X OCH 3 



and vanillin, OH.C 6 H 3 <^ , into vanillinic acid (Y. KOTAKE S ). 



X5HO 



Reductions may also occur and examples of this kind are the conver- 

 sion, as observed by E. MEYER, 4 of nitrobenzene, C 6 H 5 NO 2 , or of nitro- 

 phenol, HO.06H 4 .NO 2 into aminophenol, HO.C 6 H 4 .NH 2 , and also the 

 behavior of w-nitrobenzaldehyde in the animal body as mentioned below. 



1 Friedmann, Hofmeister's Beitrage, 11; Dakin, Journ. of biol. Chem., 4, 419. 



2 L. Nencki, Arch. f. exp. Path. u. Pharm., 1; Nencki and Ziegler, Ber. d. deutsch. 

 chem., Gesellsch., 5. See also O. Jacobsen, ibid., 12. 



3 Zeitschr. f. physiol. Chem., 45. 



4 Ibid., 46. 



