URINE. 99 



pose with the formation of a red coloration (decomposition 

 of the glycocoll) and an odor resembling that of the oil of 

 bitter almonds (benzonitrile). 



PIGMENTS. 



Variation in the yellow color of the urine noticed under 

 certain conditions, is attributable to the presence of different 

 pigments, the most important of which are urochrome,, 

 urobilin, and uroerythrin. 



UROCHROME. 



This is the name of the substance which gives to normal 

 urine its characteristic yellow color. Of its properties and 

 constitution next to nothing is known. It is isolated from 

 urine when the latter is saturated with (NH 4 ) 2 S0 4 and the 

 filtrate extracted with alcohol. The pigment is soluble 

 in the alcohol and the entire color of the urine passes into 

 the solvent. Urochrome, when acted upon by mild reducing 

 agents, yields a second pigment which is apparently identical 

 with urobilin. The name uroerythrin is applied to the pig- 

 ment which imparts to the brick-dust sediment of urates 

 (sedimentum lateritium) its pinkish coloration. Solutions 

 of this pigment are rapidly decolorized by light. 



UROBILIN. 



Although not ordinarily present to such an extent as 

 urochrome, urobilin is frequently increased in diseased 

 conditions, and its importance lies in the knowledge which 

 has been gained concerning its origin from and relation to 

 the biliary pigments. The substance is extremely soluble, 

 dissolving in all ordinary solvents. It exhibits in alcoholic 



