740 URINE. 



wise, in regard to its behavior with alkalies, with access of air, and also with 

 alkaline copper solutions and ammoniacal silver solutions, and also MILLON'S 

 reagent, it is similar to homogentisic acid. 



NEUBAUER and FLATOW, who have prepared dioxyphenyl-a-lactic acid syn- 

 thetically, find that this acid has entirely different properties from the so-called 

 uroleucic acid. GARROD and HURTLEY 1 have also shown that an impure homo- 

 gentisic acid with a low melting-point is easily obtained, and they suggest the 

 possibility that the earlier reports in regard to uroleucic acid are due to an error. 



CH COH 



HC C C.COOH 



Kynurenic acid (Y-oxy-/3-quinolincarboxylic acid), CioH 7 N0 3 , | || | 



HC C CH 



CH N 



has only been found thus far in dog's urine, but not always; its quantity is increased 

 by meat feeding. It does not occur in the urine of cats. ELLINGER 2 has been 

 able to show positively that tryptophane is the mother-substance of this acid. 

 By the introduction of tryptophane in the organism he has shown the formation 

 of a kynurenic acid not only in dogs but also in rabbits. 



The acid is crystalline, does not dissolve in cold water, rather well in hot alcohol, 

 and yields a barium salt which crystallizes in triangular, colorless plates. On 

 heating it melts and decomposes into C0 2 and kynurin. On evaporation to dry- 

 ness on the water-bath with hydrochloric acid and potassium chlorate a reddish 

 residue is obtained which on adding ammonia becomes first brownish green and 

 then emerald green (JAFFE'S reaction 3 ). 



Urinary Pigments and Chromogens. The yellow color of normal 

 urine depends perhaps upon several pigments, but in greatest part upon 

 urochrome. Besides this the urine seems to contain a very small quantity 

 of hcematoporphyrin as a regular constituent. Uroerythrin is also of 

 frequent occurrence in normal urine, but not always. Finally, the 

 excreted urine when exposed to the action of light regularly contains a 

 yellow pigment, urobilin, which is derived from a chromogen, urobilinogen, 

 by the action of light (SAILLET) and air (JAFFE, DisquE 4 ) and others. 



Besides this chromogen, urine contains various other bodies from which color- 

 ing matters may be produced by the action of chemical agents. Humin sub- 

 stances (perhaps in part from the carbohydrates of the urine) may be formed 

 by the action of acids (v. UDRANSZKY) without regard to the fact that such sub- 

 stances may sometimes originate from the reagents used, as from impure amyl 



1 Journ. of Physiol., 36. 



2 Ellinger, Ber. d. d. chem. Gesellsch., 37, 1804, and Zeitschr. f. physiol. Chem., 

 43. The older literature on kynurenic acid may be found in Josephsohn, Beitrage zur 

 Kenntnis der Kynurensaure ausscheidung beim Hunde, Inaug.- Dissert., Konigsberg, 

 1898. 



3 Zeitschr. f. physiol. Chem., 7. In regard to kynurenic acid, see also Huppert- 

 Neubauer, 10. Aufl., and Mendel and Jackson, Amer. Journ. of Physiol., 2; Mendel 

 and Schneider, ibid., 5; Camps, Zeitschr. f. physiol. Chem., 33. 



4 Jaffe", Centralbl. f. d. med. Wissensch., 1896 and 1869, and Virchow's Arch., 47; 

 Disque, Zeitschr. f. physiol. Chem., 2; Saillet, Revue de medecine, 17, 1897. 



