CHOLESTERIN. 269 



e.g., the urine, and are detected by the Gmelin-Heintz' reaction. When nitric 

 acid containing some nitrous acid is added to a liquid containing these pigments, a 

 play of colours is obtained beginning with green (biliverdin), blue, violet, red, end- 

 ing with yellow. {This reaction- is best done by placing a drop of the liquid on a 

 white porcelain plate, and adding a drop of the impure nitric acid.] 



(c) If, when the blue colour is reached, the oxidation process is arrested, bilicyanin (Heynsius, 

 Campbell), in acid solution blue (in alkaline violet), is obtained, which shows two ill-defined 

 absorption-bands near D (Jaffi). 



(d) Bilifuscin occurs in small amount in decomposing bile and in gall-stones = bilirubin 

 + H 2 0. 



(e) Biliprasin (Startler) also occurs = Bilirubin -f H 2 + 0. 



(/) The yellow pigment, which ultimately results from the prolonged action of the oxidising 

 reagent, is the choletelin (C 16 H 18 N 2 6 ) of Maly ; it is amorphous, and soluble in water, alcohol, 

 acids, and alkalies. 



[Spectrum of Bile. The bile of carnivorous animals is generally free from absorption-bands, 

 except when acids are added to it, in which case the band of bilirubin is revealed. Bilirubin 

 and biliverdin yield characteristic spectra only when they are treated with nitric acid. The 

 bile of some animals yields bands, but when this is the case they are due to the presence of a 

 derivative of heematin, and MacMunn calls this body cholohaematin, which gives a three- or 

 four-banded spectrum (ox, sheep).] 



(g) Bilirubin absorbs H + H 2 (by putrefaction, or by the treatment of alkaline 

 watery solutions with the powerfully reducing sodium amalgam), and becomes con- 

 verted into Maly's hydrobilirubin (C 32 H 40 N 4 O 7 ), which is slightly soluble in water, 

 and more easily soluble in solutions of salts, or alkalies, alcohol, ether, chloroform, 

 and shows an absorption-band at b, F. This substance, which, according to Hammar- 

 sten, occurs in normal bile, is a constant colouring-matter of faeces, and was called 

 stercobilin by Vaulair and Masius, but is identical with hydrobilirubin (Maly). 

 It is, however, probably identical with the urinary pigment urobilin of Jaffe (Stokvis, 

 20). 



[The bile of invertebrates contains none of the bile-pigments present in vertebrates, although 

 hsemochromogen is found in the cray-fish and pulmonate molluscs. In some organs, and in bile, 

 a pigment like vegetable chlorophyll entero- chlorophyll is found, but whether it is derived 

 from without, or formed within the organism, is not certain (MacMunn).'] 



(4) Cholesterin, C 26 H 44 0(H 2 0), is a monatomic alcohol which rotates the ray of 

 polarised light to the left, it occurs also in blood, yelk, nervous matter [and gall- 

 stones]. It forms transparent rhombic plates, which 

 usually have a small oblong piece cut out of the corner 

 (fig. 196). It is insoluble in water, soluble in hot alcohol, 

 ether, or chloroform. It is kept in solution in the bile 

 by the bile-salts. 



Preparation. It is most easily prepared from so-called white 

 gall-stones, which not unfrequently consist entirely of cholesterin, 

 by extracting them with hot alcohol after they are pulverised. 

 Crystals are excreted after evaporation of the alcohol. Tests. $. , q,* 



They give a red colour with sulphuric acid (5 vol. to 1 vol. H 2 0), n . * .' , . 

 while they give a blue as cellulose does with sulphuric acid and Crystals ot cholesterin. 

 iodine. When dissolved in chloroform, one drop of concentrated sulphuric acid causes a deep 

 red colour (H. Schiff). 



(5) Amongst the other organic constituents : Lecithin ( 23), or its decomposi- 

 tion-product, neurin (cholin), and glycero-phosphoric acid (into which lecithin may 

 be artifically transformed by boiling with baryta) j palmatin, stearin, olein, as 

 well as their soda soaps ; diastatic ferment ; traces of urea ; (in ox bile, acetic acid 

 and propionic acid, united with glycerine and metals, Dogiel). 



(6) Inorganic constituents of bile (0*6 to 1 per cent.) : 



They are sodic and potassic chloride, calcic and magnesic phosphate, and much iron, which 

 in fresh bile gives the ordinary reactions for iron, so that iron must occur in one of its oxidised 

 compounds in bile ; manganese and silica. Gases. Freshly-secreted bile contains in the dog 

 more than 50 vol., and in the rabbit 109 vol. per cent. C0 2 , partly united to alkalies, partly 

 absorbed, the latter, however, being almost completely absorbed within the gall-bladder. 



