CHAP. IV.] HYDROBILIRUBIN. 327 



Vierordt 1 has examined hydrobilirubin spectro-photometrically 

 both when dissolved in alcohol and in a solution of ammonia. In 

 the case of the former the maximum absorption is between X519'5 

 and X501'2 ; in the case of the latter between X5011 and X486'l 2 . 



Biliary Urobilin (?). 



Jaffe 3 by treating the bile of the dog or its alcoholic extract with 

 dilute hydrochloric acid, obtained a reddish-yellow filtrate which possessed 

 spectroscopic characters which resembled those of a pigment which he 

 found in normal and pathological urines and to which he subsequently 4 

 ascribed the name of urobilin. 'MacMunn 5 by treating the bile of various 

 animals (man, pig, ox, sheep, mouse) with alcohol and acetic acid, filtering, 

 diluting the filtrate with water and shaking with chloroform observed 

 that an orange solution is sometimes obtained. He evaporated this 

 coloured solution on the water bath and extracted the residue with rectified 

 spirit. The solution possessed two bands very like those of hydrobilirubin. 

 With ammonia and zinc chloride it assumed a red colour which on 

 exposure to air exhibited a green fluorescence. This pigment is according 

 to MacMunn probably formed in the liver from hydrobilirubin-like products 

 carried to it from the intestine by the portal blood. 



It is well to point out, however, that the bile of no animal during life 

 or immediately after death exhibits characters which entitle us to admit 

 the existence of a biliary urobilin and that by the methods employed by 

 Jaffe and by MacMunn secondary products are formed which we have no 

 right to class amongst proximate principles. Of such a nature is, without 

 a shadow of doubt, biliary urobilin. 



The subject of urobilin, or rather of the urobilinoid bodies, will be 

 considered in connection with the urinary pigments. In this place it will 

 be merely remarked that according to the majority of physiological 

 chemists, these bodies which have never been obtained in a pure condition 

 or, in a strictly scientific sense, proved to be individual substances are, if 

 not identical with, yet immediately related to, the product which Maly 

 obtained by the action of reducing agents on bile, and to which he ascribed 

 the name of hydrobilirubin. With this view the Author entirely concurs. 

 MacMunn who has paid great attention to this subject, is of a different 

 opinion. 



It appears, however, inadmissible to draw far-reaching conclusions as 

 to the existence, origin, identity and relations of complex organic bodies 

 merely from the study of the absorption spectra, or rather of the absorption 



1 Vierordt, ' Die Anwendung des Spectralapparates zur Photometric der Absorption- 

 spectren.' Tubingen, 1873. 



' 2 The original observations of Vierordt on the absorption spectra of hydrobilirubin 

 are reprinted in the work entitled Kolorimetrie und quantitative Spectralanalyse in 

 ihrer Anwendung in der Chemie von Dr Gerhard Kriiss, a. o. Professor der Chemie in 

 der Kgl. Universitat in Miinchen und Dr Hugo Kriiss in Hamburg. Hamburg and 

 Leipzig, 1891. Eefer to pages 214 and 215. 



3 M. Jaff^, 'Beitrag zur Kenntniss der Gallen und Harnpigmente,' Centralblatt 

 f. d. med. Wissenschaft, Vol. vi. (1868), pp. 240245. 



4 Jaffe, ' Zur Lehre von den Eigenschaften und der Abstammung der Harnpigmente,' 

 Virchow's Archiv, Vol. XLVII. (1869), pp. 405427. 



8 MacMunn, Proceedings of the Royal Society, 1880, No. 208. 



