UROCHROME 141 



urochrome and hsematin and urobilin. Direct evidence of 

 the cyclic nature of urochrome may perhaps be seen in the 

 striking diazo-reaction of urochromogen. (A color reaction, 

 less brilliant however, is given by the diazo-compounds with 

 formed urochrome; it corresponds closely with the diazo- 

 reaction of the normal urine. 60 ) The fact that when uro- 

 chrome is boiled with hydrochloric acid melanin-like prod- 

 ucts ("uromelanin") may be formed 61 is, if the author is 

 correct in his previous statements as to the nature of 

 melanin production (v. Vol. I of this series, p. 526, et seq., 

 Chemistry of the Tissues), certainly not contradictory of a 

 cyclic character of urochrome. It suggests, too, that certain 

 ring-form groups in the protein-molecule escape complete 

 dissociation in the course of metabolism and may finally 

 appear as urinary coloring materials. In the author's 

 laboratory there are in course at present certain experiments 

 bearing upon a possible part taken by histidin in the con- 

 struction of urochrome ; an idea suggested by the fact that 

 this compound is distinguished among the molecular cleav- 

 age products (as also tyrosine) by responding to the diazo- 

 reaction. 



True Urochrome and DombrowsJci's Urochrome. The 

 marked tendency to undergo decomposition shown by 

 the yellow coloring substance of the urine, is, moreover, 

 the cause of the differences of opinion obtaining between 

 M. Weiss and the Polish authors with reference to it. While 

 the latter authors look upon the urochrome discovered by 

 themselves as the peculiar urinary coloring matter, Weiss, as 

 stated, differentiates between true urochrome and the uro- 

 chrome of Dombrowski. The impression is that this latter 

 product, which is isolated from urine by precipitating it by 



60 K. Feri (Chvostek's Clinic, Vienna) recommends substitution of the 

 Ehrlich reagent by azophen red, that is, paranitrodiazobenzolsulphate 



eHt N = N ) 2 S'O 4 ; Wiener klin. Wochenschr., 1912, No. 24. 

 81 J. Dombrowski, Zeitschr. f . physiol. Chem., 54, 188, 1907 ; 62, 358, 1909. 



