92 BILIARY CALCULI. 



Boil a portion of the calculus with alcohol ; it is dis- 

 solved, and on cooling deposits crystals of cholesterine. 

 These features characterise the pellucid or pure chole- 

 sterine calculus. 



2. The calculus is coloured blackish brown or green, 

 and contains a coloured nucleus. It burns like the 

 former at first, but is with difficulty consumed, leaving 

 a notable amount of ash. Extract cholesterine by ether, 

 and test the coloured residue with dilute hydrochloric 

 acid. From the washed residue extract Mlifuscine with 

 alcohol, and bilirubine with chloroform. The insoluble 

 residue on combustion and the hydrochloric extract on 

 evaporation will yield earths and their phosphates, 

 particularly calcium and magnesium. This bearing 

 characterises mixed calculi with prevalence of cho~ 

 lesterine. 



3. The calculus is dark red or brown, rough, 

 fissured, without fatty feel, and easily broken. A 

 portion heated on platinum foil evolves a disagreeable 

 odour of burnt feathers and leaves an ash. Treat a 

 portion with water and hydrochloric acid and chloro- 

 form at the same time. The chloroform will become 

 red from dissolved bilirubine. Evaporate the chloro- 

 form solution on a white plate, and add a drop of red 

 nitric acid to the yellow residue, and observe the play 

 of colours peculiar to the colouring matter of bile. These 

 reactions characterise the calculi mth prevalence of 

 cholochrome 9 which occur rarely in man, but are the 

 only calculi hitherto observed in cows and oxen. 



4. The calculi are small and black or dark green, 

 and insoluble in most solvents, except boiling nitric? 



