KYNURENIC ACID. 



249 



is suggestive of a deficiency in aromatic groups in the mole- 

 cule, and it is not unlikely that this fact may account for the 

 absence of the related compound kynurenic acid (oxyquinoline- 

 carboxylic acid) when gelatin exclusively is fed. (Cf. Dogs 

 E, F.) Out of 905 grams gelatin fed to small dogs in four- 

 teen days we have obtained only 0.015 gram kynurenic acid, 

 and that on a single day. Moreover, the nitrogen determina- 

 tions in the urine (cf. Dogs E, F, G, H) give evidence of a 

 ready absorption of the gelatin ingested ; while the experiments, 

 including simultaneous feeding of typical proteids like casein 

 and albumin with the gelatin, show that the latter exercises no 



DOG J. SUMMARY. 



specific action in preventing kynurenic acid excretion when 

 sufficient proteid is given along with it. Indeed, the behavior 

 of gelatin precisely resembles that of the carbohydrates and 

 fats. These experiments considered in connection with Lusk's 

 observations indicate that the essential physiological peculiari- 

 ties of gelatin are to be sought in the chemical structure of 

 the nitrogenous portion of the molecule ; and the failure of the 

 albuminoid to give rise to kynurenic acid hi the dog is doubt- 

 less associated with the lack of certain aromatic radicals in its 

 make-up. Lastly, attention is directed to the ready assimilation 

 of crystallized vegetable proteid (Dog C), and to the evidence 



with gelatin and tyrosin (Sitzungsber. d. morphol.-physiol. Gesellsch. in Miin- 

 chen, 10 Marz, 1885). Contrary to the current statements, cf. Neumeister, 

 Lehrbuch der physiol. Chemie, 1897, p. 63, pure gelatin gives a reaction with 

 Millon's reagent which may perhaps be due to a far smaller proportion of 

 aromatic radicals than is present in ordinary proteids. See Van Name, Jour- 

 nal of Experimental Medicine, 1897, ii, p. 128. 



