240 BILIRUBIN. 



red in man and carnivora, and more or less bright green in herbi- 

 vora. These colours are due to the presence of a pigment known 

 as bilirubin in the first case and biliverdin in the second ; but 

 since the latter pigment may be readily formed by simple oxida- 

 tion from the former, bile may frequently contain both these 

 colouring-matters and hence possess a colour intermediate to the 

 above though usually with a preponderance of either the golden- 

 red or green shade. In addition to these two pigments others 

 are occasionally present in bile, as evidenced by the fact that 

 while neither bilirubin nor biliverdin exhibits any absorption 

 bands when examined spectroscopically, fresh bile of herbivora 1 

 frequently does show bands, due to substances of which but little 

 is known beyond these spectroscopic appearances (see below). It 

 is possible that the bile-pigments of different animals may ulti- 

 mately be found to differ slightly but distinctly in their composi- 

 tion, much in the same way that the bile-acids as already stated 

 differ ; but as yet no such distinct differences have been made out, 

 and we may therefore treat of them as being identical from what- 

 ever source they have been obtained. 



1. Bilirubin. C 16 H 18 N 2 O a . 3 



It occurs chiefly and characteristically in the fresh bile of man 

 and carnivora, to which it imparts the well-known golden-red 

 colour. It frequently constitutes the larger part of some kinds 

 of gall-stones, more especially of the ox and pig, not as free bili- 

 rubin but as a compound with chalk, and amounting to some 40 

 p.c. of the concretions. (Maly.) 3 It is also found in the urine 

 in icterus, also constantly in the serum from horses' blood, though 

 not from that of man or the ox, 4 and frequently as crystals under 

 the name ' hsematoidin ' (see above) in old blood-clots (extrava- 

 sations) and fluids from ovarial and other cysts. Bile-pigments 

 are also stated to occur normally in the urine of dogs, more par- 

 ticularly in the summer. 5 



Bilirubin is insoluble in water and almost insoluble in either 

 ether or alcohol, though distinctly more soluble in alcohol than 

 in ether. It is on the other hand readily soluble in alkaline solu- 

 tions, hence its solution in bile, also in glycerin carbon-disulphide, 



1 Bile of carnivora does not usually show bands until it has been treated with an 

 acid. 



2 This is the generally accepted formula, assigned to this substance by Maly. ./. 

 f. prakt. Chem. Bd. civ. (1868), S. 28, confirming Staedeler. It is possible that the 

 formula is really twice the above, viz. C 32 H 3 ~,N 4 O 6 , as required to represent the 

 formula of a well-defined tribromo-substitution product, C 32 H 33 Br 3 N 4 6 . This 

 doubling of the formula is also necessarv to express the derivation of hvdrobilirubin. 

 (C 32 H 40 N 4 O 7 ) from bilirubin. Maly, Sitzb. d. k. Akad. d. Wiss. Wien. in. Abth. 

 Oct.-Hft. 1875. Liebig's Anna!. Bd* CLXXXI. (1876), S. 106. 



3 See earlier Staedeler, Vierteljahrschr. d. naturforsch. Gesetl. Ziirich, Bd. viu- 

 1863, and Liebig's Annul. Bd. cxxxn. (1864), S. 323. 



4 Hammarsten (Swedish). See Abstr. in Maly's Jahresb. 1878, S. 129. 

 8 Salkowski u. Leube, Die Lehre vom Harn, 1882, S. 246. 



