vii KATABOLIC CONSTITUENTS OF UEINE 399 



intestine is eliminated with the faeces, the remainder is absorbed 

 and carried by the portal vein to the liver, where it is partially 

 poured out again into the intestine with the bile, partially traverses 

 the hepatic veins and is excreted with the urine (Kiva). 



It is possible from daily determinations of the quantitative 

 fluctuations of the urobilinogen content of the urine and faeces, 

 together with estimations of the variations in the haemoglobin 

 content and number of erythrocytes in the blood, to calculate the 

 value of the haemoglobin exchange, i.e. the extent to which the 

 haemoglobin is destroyed and formed again (Zoja). The bilinogen 

 content of the urine and faeces increases after hard muscular work, 

 in fevers, and, generally speaking, with exaggerated haemolysis, 

 and diminishes during convalescence from febrile maladies and 

 in chlorosis. 



According to Riva's interesting studies, the urobilinogenesis is 

 in strict relation with the quantity of bilirubin secreted by the 

 liver-cells. Estimation of the urobilin content of the urine and 

 faeces therefore gives a criterion of the normal or more or less 

 degenerated hepatic cells. The persistence of the urobilin (and 

 still more its increase) must' indicate a favourable prognosis, even 

 in serious cases of hepatic disease. This theory of Riva is confirmed 

 by observing the way in which the formation of urobilinogen alters 

 in the course of intoxication by phosphorus and nitric acid. 



The possibility is not, however, excluded of a certain amount 

 of urobilin and its chromogen being formed, along with other bile 

 pigments, by the metabolic activity of the hepatic cells (Hayeni), 

 and also by the reducing action exerted on the bile pigments by 

 the various tissues, especially the kidneys (Quincke, Kiener, 

 Engel, Mya). This view, which assumes in addition to the 

 intestinal, a hepatic and renal origin for urobilinogen, is supported 

 by the fact that in the descending phase of cholaemia bilirubin 

 alone is found in the blood, urobilin alone in the urine, which can 

 be explained on the assumption that the first is converted by the 

 action of the renal epithelia into the second. 



Urobilin must not be confounded with the pigment that pro- 

 duces the dull red colour of the urate sediment. This comes from 

 the uroerytlirin present in minute quantities in normal urine, to 

 a larger extent in fibrile urine. Uroerythrin has specific chemical 

 and spectroscopic characteristics which differ from those of 

 urobilin. Probably it is contained in the urine as a sodium salt 

 in combination with the urates. 



The genesis of uroerythrin and its relations with Garrod's 

 urochrome and urobilin are unknown. According to Riva, Prima- 

 vera and Reale, uroerythrin is found particularly in diseases of 

 the liver (cirrhosis), and generally in all morbid conditions in 

 which urobilinuria is present. It is probable from clinical observa- 

 tions that the presence of uroerythrin connotes some alteration of 



