308 THE URINE. 



origin of the normal urinary pigments. The chemical position of 

 the colorless mother-substance of urobilin, moreover, which is spoken 

 of as urobilinogen, and which can usually be demonstrated when- 

 ever urobilin also is present, is thus far not clear. 



According to Garrod, the urobilin of the urine is identical with 

 the stercobilin of the feces, both in composition and properties, but 

 differs conspicuously from hydrobilirubin, especially in the much 

 smaller percentage of nitrogen which it contains, viz., 4.11 per cent., 

 as compared with 9.22. The elementary composition of urobilin is 

 given by Garrod and Hopkins as : C, 63.58 per cent. ; H, 7.84 ; 

 N, 4.11, and O, 24.47. Garrod further states that by acting upon 

 urochrome with acids he never succeeded in obtaining any prod- 

 uct showing the urobilin band, or yielding the well-known fluores- 

 cence with zinc chloride and ammonia, as Thudichum claimed. 

 But he found that a substance having both these properties is 

 readily obtained by the action of aldehyde upon an alcoholic solu- 

 tion of urochrome. In a short time shorter still when the liquid 

 is warmed an absorption-band appears like that of urobilin, and 

 the tint of the solution deepens to a rich orange-yellow. With zinc 

 chloride and ammonia a brilliant green fluorescence occurs, and 

 the band is shifted toward red, as that of urobilin is under like 

 conditions. 



Isolation of Urochrome. To demonstrate the presence of so-called 

 urochrome in normal urine, the fluid is acidulated with 1 or 2 c.c. 

 of dilute sulphuric acid pro liter. On filtering, it is saturated with 

 ammonium sulphate. The resulting precipitate is dried and ex- 

 tracted with warm and slightly ammoniacal alcohol. The pigment 

 passes into solution, and is obtained on evaporation of the alcohol as 

 an amorphous reddish-brown substance, which is readily soluble in 

 acidulated water, chloroform, and common alcohol, but is practically 

 insoluble in ether and benzol. According to Garrod, its solutions 

 do not give rise to any bands of absorption, and do not fluoresce 

 upon the addition of ammonia and zinc chloride. Gautier, on the 

 other hand, states that its acidulated solutions show a band of 

 absorption about F, and that the remainder of the spectrum from 

 about G on to the right is obscured. He adds that in this respect 

 urochrome and choletelin are alike. 



Garrod regards the action of aldehyde upon an alcoholic solution of 

 urochrome, outlined above, as a very delicate test for the pigment. 

 The process can be stopped then by simple dilution with water, as 

 aldehyde has no such action upon aqueous solutions of urochrome. 

 If, however, the action is allowed to continue, a further change 

 ensues. The liquid reddens and a second band appears in the violet. 

 The fluorescence can still be obtained with zinc chloride and ammonia, 

 and both bands are shifted toward red and are closer together than 

 before. 



The term uroerythrin has been applied to the pigment which 

 imparts the salmon-red color to sediments which are composed of 



