CHEMICAL BASIS OF THE ANIMAL BODY. 241 



in the first case and biliverdin in the second ; but since the latter 

 pigment may be readily formed by simple oxidation 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 

 ultimately be found to differ slightly but distinctly in their composition 

 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 whatever source 

 they have been obtained. 



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



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 bilirubin 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 ' haematoidin ' (see above) in old 

 blood-clots (extravasations) and fluids from ovarial and other cysts. 

 Bile-pigments are also stated to occur normally in the urine of dogs, 

 more particularly 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 solutions, hence its 

 solution in bile, also in glycerin carbon-disulphide, and benzol, and 



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. Jn. 

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

 formula is really twice the above, viz. CggHggN^g 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 necessary to express the derivation of hydrobilirubin 

 (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 Annal. Bd. CLXXXI. (1876), S. 106. 



3 See earlier Staedeler, Vierteljahrschr. d. naturforsch. Gesell. Zurich, Bd. viu. 

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



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



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



