KYNURENIC ACID. 247 



dose of eight grams of borax produced a nitrogen deficit of 

 over four grams. Uric acid, however, was continually present 

 in the urine of the dogs employed ; and the results obtained 

 are in harmony with the opinion that kynurenic acid excretion 

 is a phenomenon accompanying pronounced stimulation of 

 proteid katabolism rather than ordinary conditions of body 

 equilibrium. 



The gelatin experiments. Eckhard * stated that after feeding 

 gelatin to a dog he failed to find kynurenic acid in the urine. 

 Rosenhain f likewise obtained no kynurenic acid after feeding 

 two and a half pounds of gelatin and six pounds of bread to 

 a large dog in the course of a week. After a meal of one 

 kilo of meat, however, the same animal excreted as much as 

 0.995 gram of kynurenic acid during the succeeding twenty-four 

 hours. No data are presented to show that the gelatin was 

 absorbed satisfactorily. 



The results obtained with gelatin feeding in the present 

 investigation afford an interesting confirmation of previous 

 observations. The experiments of J. Munk | have shown 

 that in dogs over two-thirds of the required proteid of the diet 

 may be replaced by gelatin with maintenance of nitrogenous 

 equilibrium. Gelatin is, as a rule, readily digested and burned 

 in the body, and has a pronounced proteid-sparing action like 

 a typical non-proteid food. Lusk and his co-workers have 

 recently shown that gelatin like the proteids proper 

 may yield 60 per cent of sugar in the metabolic changes it 

 undergoes in the body, as was evidenced by the amount of 

 sugar excreted when the albuminoid was fed to a fasting 

 animal in phlorhizin diabetes. Gelatin differs chemically from 

 the ordinary proteids, in that tyrosin has not been found 

 among its decomposition products. The absence of tyrosin 



* Eckhard, Ann. Chem. Pharm., 1856, xcvii, p. 358. 



t Bosenhain, Beitrage zur Kenntniss der Kynurensaurebildung im Thier- 

 korper. Inaugural-Dissertation. Konigsberg, 1886, p. 8. 



\ J. Munk, Arch. f. d. ges. Physiol., 1894, Iviii, p. 309. 



Halliburton, Schaefer's Physiology, 1898, i, p. 71. It may be added that 

 K. B. Lehmann failed to accomplish proteid synthesis in rats by feeding them 



