EXAMINATION OF BILIARY CALCULI. 91 



angles. These appear beautifully formed when they have 

 separated spontaneously from old exudates, transudates, or 

 cystic fluids. 



(6) Place a small quantity of the cholesterin crystals on 

 a slide, put on the cover-glass, and let a drop of a mixture of 



FIG. 6. Cholesterin from Cystic Fluid. 



five volumes of concentrated sulphuric acid and one volume 

 of water flow under the cover-glass from the side and then a 

 very small quantity of a solution of iodine; the cholesterin 

 crystals gradually turn brown or violet, sometimes even a 

 clear blue, and partially dissolve. The coloring never appears 

 entirely uniform and is often incomplete. 



(c) Use the greater part of the cholesterin for the follow- 

 ing reactions: 



1. Evaporate a small quantity on the cover of a porcelain 

 crucible with hydrochloric acid and a trace of ferric chloride: 

 blue color. 



2. Chloroform Sulphuric Acid Reaction. Dissolve some 

 cholesterin in a dry test-tube in a few cubic centimeters of 

 chloroform, add an equal volume of concentrated sulphuric 



