358 



C'HOLESTERIN. 



[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, bili- 

 Cyanin (Heynsius, Campbell), in acid solution blue, (in alkaline violet) is obtained, 

 which shows two ill-defined absorption-bands near D (Jaffe). Capranica advises 

 that the acid fluids be shaken with a mixture of chloroform and alcohol (1 : 1). 

 This mixture absorbs the pigment ; pour off the fluid and add bromine in alcohol 

 (^ p.c.), and the play of colour is obtained. 



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

 = bilirubin + H 2 O. 



(e.) Biliprasin (Stadler) also occurs = bilirubin + H 2 O + 0. 

 (/.) The yellow pigment, which 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. 



(g.} Hydro-bilirubin. Bilirubin absorbs H + H 2 (by putrefaction, 

 or by the treatment of alkaline watery solutions with the powerfully 

 reducing sodium amalgam), and becomes converted into Maly's hydro- 

 bilirubin (C 32 H 14 N 4 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, accord- 

 ing to Hammarsten, occurs in normal bile, is a constant colouring- 

 matter of faeces, and was called stercobilin by Vaulair and Masius, but 

 is identical with hydro-bilirubin (Maly). It is, however, probably 

 identical with the urinary pigment urobilin of Jaff6 (Stokvis, p. 35). 

 (4.) Cholesterin, C 20 H 44 (H 2 0) is an alcohol which rotates the 



ray of polarised light to the 

 left, and whose constitution is 

 unknown; it occurs also in 

 blood, yelk, nervous matter, and 

 [gall-stones]. It forms trans- 

 parent rhombic plates, which 

 usually have a small oblong 

 piece cut out of one corner 

 (Fig. 145, a). It is insoluble in 

 water, soluble in hot alcohol, in 

 ether, and 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 con- 

 sist almost entirely of cholesterin, by 

 extracting them with hot alcohol after 

 they are pulverised. Crystals are 

 excreted after evaporation of the 

 alcohol, and they give a red colour 



Crystals 

 laminated ; 



Fig. 145. 



of Cholesterin a, regularly 

 b, irregularly laminated, 



partially injured forms ; x 300 (Aitkeu 

 after Wedl). 



