EXCRETION OF KYNURENIC ACID. 227 



not accomplished.* It cannot be assumed that kynurenic 

 acid completely replaces uric acid in the urine of the dog, 

 inasmuch as the experiments of Solomin f have shown that 

 both acids may occur together under appropriate conditions, 

 and our own experience leads to a similar conclusion. Solo- 

 min found that although the uric acid nitrogen (determined 

 by the Ludwig-Salkowski method) forms only a very small 

 fraction of the total nitrogen excreted, the quantity of uric 

 acid estimated per kilo of body weight may be as large as 0.01 

 gram, which corresponds with the average uric acid output 

 per kilo in man. In the case of dogs in nitrogenous equili- 

 brium, numerous experiments in this laboratory have given a 

 considerably smaller excretion (0.003-0.004 gram per kilo)4 

 The higher figures obtained by Solomin are perhaps attribu- 

 table to the rather large quantities of proteid fed. 



Regarding the immediate origin of kynurenic acid, little of 

 a positive character is to be found in physiological literature. 

 Its close relation to the diet, and its ready production after the 

 ingestion of meat, have frequently been pointed out. Thus 

 Schmidt || believed to have found kynurenic acid excretion to 

 be greatest after feeding meat, and least with a bread diet, a 

 milk diet yielding intermediate results. His figures for the 

 various dietaries, are, however, by no means comparable, since 

 the quantities of the typical food-stuffs ingested in the three 

 periods were not at all equivalent.^ The experiments of 



* Cf . for example, Voit and Riederer, Zeitschrift fur Biologic, 1865, i, p. 316. 



t Solomin, Zeitschr. f. physiol. Chemie, 1897, xiii, p. 497. 



} Cf. Chittenden, Journal of Physiology, 1891, xii, p. 220. Chittenden and 

 Gies, Amer. Journ. Physiol., 1898, i, p. 1. 



The daily diet of the 9-kilo dog consisted of meat, 400 grams; milk, 

 250 c.c. ; and NaCl, 10 grams (loc. cit., p. 498). Regarding the increase in uric 

 acid excretion following the ingestion of proteid, cf. Schultze, Arch. f. d. gee. 

 Physiol., 1889, xlv, p. 401 ; Herter and Smith, New York Medical Journal, 

 June 4, 1892 ; Hopkins, Schaefer's Physiology, 1898, i, p. 594. 



|| Schmidt, Ueber das Verhalten einiger Chinolinderivate im Thierkorper 

 mit Riicksicht auf die Bildung von Kynurensaure. Inaugural-Dissertation. 

 Konigsberg, 1884. (Jaffe's laboratory.) 



1 The dog was fed (a) meat, 1 kilo, (b) milk, 2 liters, (c) bread, 1 pound, 

 respectively, per day. 



