278 URINE. [CH. XII. 



C. The Pigments of Urine. 



Urochrome is the chief pigment of normal urine. 

 It is a yellow substance which has no definite absorption 

 band. Nothing certain is known as to its constitution or 

 origin, except that it is apparently not derived from the 

 bile pigments. It has marked reducing properties. 



Urobilin occurs in fresh normal urine as its chromo- 

 gen, urobilinogen. This is converted into urobilin by acids 

 or by the action of light and oxygen. The amount 

 excreted is markedly increased in fevers, in diseases of 

 the liver and bile passages, by destruction of the red 

 corpuscles, especially in pernicious anaemia and malaria, 

 and during the absorption of blood clots. In certain of 

 these cases the urobilin itself is found in the urine, and can 

 be identified by its characteristic absorption band, urobilin- 

 ogen not giving a definite band. 



Urobilinogen is a pyrrol body and is responsible for 

 Ehrlich's reaction with ^-dimethyl-amino-benzaldehyde. 



The origin of urobilin from the bile pigments is dis- 

 cussed on page 267. It may be added that the urobilin 

 absorbed from the bowel into the circulation is mostly 

 excreted by the liver into the bile, so that only a small 

 portion reaches the urine. Should the liver cells be 

 injured, or should there be any interference with the 

 circulation through the liver, there is a considerable increase 

 in the excretion of either urobilin or urobilinogen in the 

 urine. 



If the common bile duct is completely occluded by a 

 gall stone or by a growth the urobilin and urobilinogen are 

 absent from the urine and faeces. Should the obstruction 

 be removed there is often a period during which the 

 amounts of these substances in the urine is exceptionally 

 large. 



Uroerythrin is found in small amounts in normal 

 urine. It is increased in fever and certain diseases of the 

 liver. 



