KYNURENIC ACID. 245 



and of Reilly, Nolan and Lusk* indicate that most of the 

 nitrogen of ingested meat is, on the other hand, eliminated 

 within a few hours. It may be imagined, then, that kynu- 

 renic acid is one of the nitrogenous products derived from 

 this rapidly eliminated nitrogenous radical of the original 

 proteid ; and it scarcely seems unreasonable to assume that 

 this acid represents the metabolic end-product of quinoline- 

 yielding radicals in the molecule.f In this connection it will 

 be remembered that R. Cohn J was able to obtain a pyridine 

 derivative as a decomposition product of casein, thus demon- 

 strating the possible presence of the pyridine ring in the con- 

 stitution of the proteid molecule. 



Granting conditions like those referred to, several probabili- 

 ties are indicated. For example, it should follow that the 

 extent of proteid katabolism going on should influence very 

 largely the production of kynurenic acid. Our experiments 

 with non-nitrogenous diet (fat and carbohydrate) are quite 

 in harmony with this. Excessive proteid decomposition is 

 avoided under such conditions, and kynurenic acid rapidly 

 disappears from the urine. (Cf. Dog A, B.) Equally sug- 

 gestive are the results obtained with a mixed diet containing 

 only small amounts of proteid. The proteid-sparing effect of 

 the other food-stuffs is here well brought out. In one animal 

 (Dog A) an absence of kynurenic acid excretion during the 

 first seven days of starvation was noted. The observation 

 was an exceptional one, but perhaps not without significance, 

 since the animal had an unusually well-nourished appearance, 

 and the " fat " condition was remarkably persistent, even during 

 the later days of starvation. We are inclined to attribute the 

 results to the rather exceptional condition of the animal, since 

 it is well known that the extent of nitrogenous katabolism 

 in inanition is modified in a pronounced way by the relative 

 as well as absolute amount of body fat in the individual. 



* Reilly, Nolan and Lusk, loc. cit., p. 404 fig. 

 t Cf. also Kretschy, Monatshefte fur Chemie, 1881, ii, p. 85. 

 } R. Cohn, Zeitschr. f. physiol. Chemie, 1896, xxii, p. 171. 

 Cf. Munk and Ewald, Die Ernahrung, 1895, pp. 22-23. 



