914 APPENDIX. 



Biliverdin. C 16 H 18 N 2 4 . l 



This product of the oxidation of bilirubin gives the characteristic color to the bile 

 of herbivora and to biliary vomits. It occurs also probably at times in the urine of 

 jaundice and in the pigmentary matter of the placenta. It is found, or occurs in 

 traces only, in gall-stones. 



Preparation. An impure product is obtained by precipitating ordinary herbiv- 

 orous bile with baric chloride, washing the precipitate with water and alcohol, and 

 decomposing it with hydrochloric acid. The biliyerdin thus obtained is washed with 

 ether and dissolved in alcohol. From its solution in the latter it is obtained as an 

 amorphous green powder by slow evaporation. Pure biliverdin is best prepared by 

 the slow oxidation in the air of bilirubin, dissolved in dilute caustic soda. 



It does not crystallize, and is insoluble in ether or chloroform ; readily soluble in 

 alcohol. When oxidized it gives the same play of colors as does bilirubin, with the 

 formation of the same final and intermediate products. 



Neither this body nor bilirubin gives any characteristic absorption bands. 



There seems now no reason for doubting that the bile pigments are derived ulti- 

 mately from the coloring matter of the blood. 



Virchow has described 2 the gradual changes in old blood-clots, as of cerebral 

 hemorrhage, which lead to the presence of the so-called hsematoidin-crystals. 

 Though these have not been obtained in sufficient quantities to enable their 

 composition to be finally fixed by a chemical analysis, 3 still the identity of their 

 crystalline form with that of bilirubin, and the fact that they both give the same 

 play of colors when oxidized, as in Gmelin's test, justify the assumption that 

 haematoidin and bilirubin are identical. 4 Moreover, the balance of experimental 

 evidence distinctly supports the view that a liberation from the corpuscles of the 

 coloring matter of the blood in the bloodvessels by an injection of chloroform, 

 water, etc., leads generally to the appearance of bile-pigments in the urine. 5 The 

 occurrence of bilirubin crystals in the urine has frequently been observed after 

 the operation of transfusion of blood in man. The chemical possibility of the con- 

 version of haemoglobin into biliverdin is readily seen by a comparison of the formulae 

 of haematin (see p. 464) and bilirubin. The former has, according to Hoppe-Sey- 

 ler, 6 the composition indicated in the formula 2 (Cg^gN^FeCy, while that of bili- 

 rubin is Ci 6 H 18 N 2 3 . Although the conversion has not as yet been directly effected, 

 the following facts are significant : If bilirubin is treated with sodium amalgam the 

 substance known as hydrobilirubin (see below) is obtained. If haematin 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 recognized as identical with 

 hydrobilirubin. 7 This is the most direct chemical evidence of the relation of the 

 coloring matters of the blood and bile. 



Choletelin. C 16 H 18 N 2 6 (?). 8 



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 colors of Gmelin's reaction are observed and the 

 final red dish-yellow solution, if poured into water, yields a precipitate of choletelin. 

 It is not crystalline and is soluble in alcohol, ether, and chloroform. When freshly 

 prepared it seems to give an uncertain absorption band if examined in an acid solu- 

 tion. On this account some observers 9 have been led to regard it as identical with 

 hydrobilirubin (urobilin). There is, however, no doubt that they are quite distinct 

 bodies. 10 



1 Maly, Sitzb. d. Wien. Akad., Ed. Ixx. (1874). iii. Abth. 



2 Arch. f. path. Anat., Bd. i., S. 383. 



3 Robin, Ann. d. Chem. u. Pharm.,Bd.cxvi.,S. 89. 

 * But see also Preyer, Die Blutkrystalle, 1871, S. 187. 



5 Tarchanoff, Pfliiger's Arch., Bd. ix. (1874), S. 53. See also Bd. x. (1875), S. 208. 

 e Physiologische Chemie, 1879, S. 395. 



T Hoppe-Seyler, Med.-chem. Untersuch., Heft iv., 1871, S. 523. Ber. d. Deutsch. chem. Gesell., 

 Vii. (1874), S. 1065. 



7 Hoppe-S 

 i. (1874), S. 



8 Maly, Si 



aly, Sitzb. d. Wien. Akad., Bd. Ivii. (1868) ; 2 Abth. Febr. und Bd. lix., 1869 ; 2 Abth. April. 

 See also Heynsius and Campbell, loc. cit. 



9 Heynsius and Campbell, loc. cit. Stokvis, Centralbl. f. d. med. Wiss., No. 14 (1873), S. 211. 



10 Maly, Centralbl. f. d. med. Wiss., No. 21 (1875), S. 321. Liebermann, Pfliiger's Arch., Bd. xi. 

 (1875), S. 181. 



