THE LIVER. 165 



it appears as a mass of white plates which shine like mother-of- 

 pearl and have a greasy feel. 



Cholesterin is insoluble in water, dilute acids and alkalies. It is 

 neither dissolved nor changed by boiling caustic alkali. It is easily 

 soluble in boiling alcohol and crystallizes on cooling. It dissolves 

 readily in ether, chloroform, and benzol, and also in the volatile or 

 fatty oils. It is dissolved to a slight extent by alkali salts of the bile, 

 acids. For the detection of cholesterin we make use of its action 

 with concentrated sulphuric acid, which, as above stated, gives a 

 colored hydrocarbon with this acid. 



If a mixture of five parts sulphuric acid and one part water acts 

 on a cholesterin crystal, this crystal will show colored rings, first a 

 bright carmine-red and then violet. This fact is made use of in the 

 microscopic detection of cholesterin. Another test, and one very 

 good for the microscopical detection of cholesterin, consists in treat- 

 ing the crystal first with the above dilute acid and then with some 

 iodine solution. The crystals will be gradually colored violet, 

 bluish green, and a beautiful blue. 



SALKOWSKI'S Reaction. The cholesterin is dissolved in chloro- 

 form and then treated with an equal volume of concentrated 

 sulphuric acid. The cholesterin solution becomes first bluish 

 red, then gradually more violet-red, while the sulphuric acid ap- 

 pears dark red with a greenish fluorescence. If the chloroform 

 solution is poured into a porcelain dish it becomes violet, then 

 green, and finally yellow. 



SCHIFF'S Reaction. If a little cholesterin is placed in a porcelain dish 

 with the addition of a few drops of a mixture of two to three vols. coiic. 

 hydrochloric acid or sulphuric acid and one vol. of a medium solution of 

 ferric chloride, and carefully evaporated to dryness over a small flame, a red- 

 dish-violet residue is first obtained and then a bluish violet. 



If a small quantity of cholesterin is evaporated to dryness with a drop of 

 concentrated nitric acid, we obtain a yellow spot which becomes deep orange- 

 red with ammonia or caustic soda (not a characteristic reaction). 



Isocholesterin. This body, so called by SCHULTZE, is isomeric with the 

 ordinary cholesterin and occurs in wool-fat, and is therefore found in abun- 

 dant quantities in so-called lanolin. It does not give SALKOWSKI'S or SCHIFF'S 

 reactions. 



We make use of the so-called cholesterin-stones in the prepara- 

 tion of cholesterin. The powder is first boiled with water and 

 then repeatedly boiled with alcohol. The cholesterin which 

 on cooling separates from the warm filtered solution is boiled with 



