THE BILE. 163 



Cholesterin usually occurs in the form of colorless, transparent 

 plates, with ragged margins and angles, which are very characteristic. 

 It is practically insoluble in water, dilute acids and alkalies, but dis- 

 solves with ease in ether, chloroform, benzol, and in boiling alcohol. 

 From its ethereal solutions it crystallizes out in the form of fine 

 needles. It is further soluble in the essential and fatty oils, as also 

 in the presence of biliary acids. Its crystals melt at 145 C. 



Tests. SALKOWSKI'S TEST. A few crystals of cholesterin are 

 dissolved in a small amount of chloroform and treated with an 

 equal volume of concentrated sulphuric acid. The solution of 

 cholesterin then first assumes a blood-red color, and then gradually 

 turns to a violet red, while the sulphuric acid appears dark red and 

 shows a green fluorescence. On pouring the chloroform into a 

 shallow porcelain dish it turns violet, then green, and finally becomes 

 yellow. 



THE TEST OF LIEBERMANN-BURCKHARD. If a small amount 

 of cholesterin is dissolved in about 2 c.c. of chloroform and is 

 treated with 10 drops of acetic acid anhydride, and subsequently 

 with concentrated sulphuric acid, the solution at first assumes a red, 

 then a blue, and finally a green color. The latter develops at 

 once if cholesterin is present only in traces. 



Isolation. To prepare cholesterin for purposes of study, it is 

 most convenient to isolate the substance from cholesterin stones. 

 To this end, the concretions are finely pulverized and extracted 

 with boiling water and then with boiling alcohol. From the 

 alcoholic extract the cholesterin crystallizes out on cooling, and is 

 then boiled with an alcoholic solution of sodium hydroxid, so as to 

 saponify the fats which are at the same time present. The alcohol 

 is then distilled off and the residue extracted with ether, which 

 removes the cholesterin and leaves the soaps behind. On evaporat- 

 ing this extract, after filtration, the substance is obtained in crystal- 

 line form, and can be further purified by recrystallization from a 

 mixture of alcohol and" ether. 



Other Organic Constituents of the Bile. In addition to the 

 bodies already described, the bile contains also small amounts of 

 lecithin, of palmitin, stearin, olein, and the soaps of the correspond- 

 ing fatty acids. In ox-bile Lassar-Cohn found also traces of 

 myristinic acid, C U H 28 O 21 , which has heretofore only been observed 

 in the spermaceti of whales. We further find traces of urea, 

 and occasionally a diastatic ferment, which is by some observers 

 regarded as identical with ptyalin. Its presence, however, is by 

 no means constant, and it can scarcely be regarded as playing a 

 role in the process of intestinal digestion. Larger amounts of urea, 

 according to Hammarsten, are found in the bile of the shark and 

 the sturgeon. 



In decomposing bile cholin, glycerin-phosphoric acid and tri- 

 methylamin may be observed, and are referable to the decomposition 

 of lecithin (see pages 65 and 66). 



