76G BILE PIGMENTS. [App. 



obtained. If hsematin is dissolved in caustic soda and treated with 

 sodium amalgam or in hydrochloric acid solution with zinc dust, a 

 substance is obtained which is now recognised as identical with hydro - 

 bilirubin 1 . This is the most direct chemical evidence of the relation of 

 the colouring matters of the blood and bile. 



Choletelin. C 16 H 18 N a O 6 (?) 2 . 



This substance is obtained as the final product of the oxidation of 

 either bilirubin or biliverdin. It is best prepared by acting upon 

 bilirubin with nitrous acid in presence of alcohol ; the various colours 

 of Gmelin's reaction are observed and the final reddish-yellow solution, 

 if poured into water, yields a precipitate of choletelin. It is not 

 crystalline and is soluble in alcohol, sether and chloroform. When 

 freshly prepared it seems to give an uncertain absorption band if 

 examined in an acid solution. On this account some observers 3 have 

 been led to regard it as identical with hydrobilirubin (urobilin). There 

 is however no doubt that they are quite distinct bodies 4 . 



Hydrobilirubin . C 32 H 40 N 4 O 7 . 



This body was first described by Maly 5 as resulting from the action 

 of sodium amalgam on an alkaline solution of bilirubin. When the 

 reaction is complete, the solution is precipitated with hydrochloric acid, 

 the precipitate dissolved in ammonia, again precipitated by acid, and the 

 substance thus finally obtained is washed with water. It is readily 

 soluble in alcohol, less so in sether. Its alkaline solutions are yellow, 

 and these turn pink on the addition of acid. Both its acid and alkaline 

 solutions, the latter especially on the addition of a few drops of chloride 

 of zinc, give a characteristic absorption band between b and F. 6 In the 

 colours of its alkaline and acid solutions and the greenish fluorescence 

 of its ammoniacal solution on the addition of chloride of zinc, and in" its 

 absorption spectrum hydrobilirubin shews its close relation to urobilin 

 (see below), with which indeed it is now considered to be identical. It 

 is also identical with a body named stercobilin 7 which had previously 

 been described, as a product of the alteration of the bile pigments in the 



1 Hoppe-Seyler, Med.-chem. Untersuch. Hft. iv. 1871, S. 523. Ber. d. deutsch. 

 cJiem. Gesell. vn. (1874), S. 1065. 



2 Maly, Sitzb. d. Wien A kad. Bd. LVII. (1868), 2 Abth. Febr. und Bd. LIX. 1869, 

 2 Abth. April. See also Heynsius and Campbell, loc. cit. 



3 Heynsius and Campbell, loc. cit. Stokvis, Centralb. f. d. med. Wiss. No. 14 

 (1873), S. 211. 



4 Maly, Centralb. f. d. med. Wiss. No. 21 (1875), S. 321. Liebermann, Pfliiger's 

 Arch. Bd. xi. (1875), S. 181. 



5 Centralb. f. d. med. Wiss. No. 54, 1871. Annal. d. Chem. Bd. CLXIII. (1872), 

 S. 77. 



Vierordt, Zeitsch.f. BioL Bd. ix. (1873), S. 160. 



7 Vanlair and Masius, Centralb. f. d. med. Wiss. No. 24, 1871. 



