248 ORIGIN OF BILE-PIGMENTS. 



characterised by one absorption band between b and F and, as he 

 then said, two other bands. 1 After the appearance of Maly's work 

 he was led to suspect that the substance he had previously de- 

 scribed was in reality identical with hydrobilirubin and therefore 

 with urobilin, a conclusion which he verified by a careful repeti- 

 tion of his earlier experiments. 2 



More recently Nencki and Sieber have prepared a similar pigment 

 by the action of hydrochloric acid and zinc on their haematoporphyrin, 

 to which latter substance, as was stated above, they assigned a formula 

 identical with that of bilirubin. They state however that the pigment 

 (urobilin) is not quite identical as obtained on the one band by the 

 action of nascent hydrogen on bilirubiu, and on the other hand on their 

 hsematoporphyrin. 3 



Assuming then the identity of these substances we have in 

 Hoppe-Seyler's work the best and most direct chemical evidence 

 of the relationship between the colouring-matters of the blood 

 and bile. For if one and the same substance, viz. urobilin, can 

 be prepared by the same means, namely reduction (hydrogena- 

 tion) from both haematin (haemoglobin) and bilirubin, these two 

 substances must be themselves closely related. It has not how- 

 ever as yet been found possible to produce a bile-pigment directly 

 from haemoglobin or haematin by any artificial process outside the 

 animal body. The derivation of the urinary pigments (urobilin) 

 from those of bile presents no difficulty when it is remembered 

 that a not inconsiderable quantity of hydrogen is present in the 

 gases of the intestine ( 282) which may be accounted for by 

 (butyric) fermentative processes (p. 105), and that this hydrogen 

 might in its nascent state readily produce the simple change 

 which is known to occur when bilirubin is converted into 

 hydrobilirubin or urobilin. And here it is interesting to note 

 that hydrobilirubin is readily absorbed and excreted in the 

 urine either when placed in the alimentary canal or injected 

 subcutaneously. 



The question of pigmentary relationships to which reference 

 has just been made suggest the present as a convenient place to 

 enter into further details on the now undoubted but once dis- 

 puted derivation of the bile-pigments from the colouring-matter 

 of blood (see 477). 



The starting point for this view was the discovery and descrip- 

 tion of haematoidin crystals by Virchow (see p. 239) as occurring 

 411 old blood-clots in parts of the body remote from the liver and 

 in which it was inconceivable that they could have arisen by any 

 process other than a gradual formation from the pigment of the 



1 Med.-chem. Untersuch. Hft. 4, 1871, S. 536. 



2 Ber. d. d. chem. Gesell. Bd. vn. (1874), S. 1065. 



3 Monatsh. f. Chem. Bd. ix. (1888), S. 115; Arch. f. exp. Path. u. Pharmakd. Bd. 

 xxiv. (1888), S. 430. 



