GALL-STONES. 469 



* 



in the interior, do not fuse on being heated, and give off a not 

 disagreeable odour. Hot water extracts a yellow matter ; 

 caustic potash dissolves them rapidly, forming a grayish brown 

 solution, from which a dull green precipitate is thrown down on 

 the addition of an acid. 



This precipitate dissolves in nitric acid, producing a red tint, 

 which rapidly changes to a yellow. Berzelius is of opinion 

 that the principal mass of bezoar consists of biliary fat and 

 resin, mixed with other fatty matter, and held together by 

 intestinal mucus. 1 



Gall-stones in Man. 



Biliary concretions are of very common occurrence in the 

 human subject. They consist principally of cholesterin with a 

 small amount of other fats, bilifellinic acid or biliary resin 

 mixed with some bile-pigment, and mucus. In analysing a 

 gall-stone, we first reduce it to a fine powder, which is a matter 

 of no difficulty, and heat it on the water-bath in order to 

 expel all moisture. The powder is then extracted with water, 

 which takes up bilin with bilifellinic acid, and probably a little 

 extractive matter ; these are obtained by evaporating the water. 

 The portion not taken up by water must be again dried and 

 treated with hot, pure ether, which extracts the fat. We eva- 

 porate the ether, and dissolve the residue in hot alcohol, from 

 which cholesterin crystallizes on cooling ; after the removal of 

 the cholesterin the evaporated alcohol yields the other fats as 

 fatty acids. The residue insoluble in ether is now extracted 

 with boiling anhydrous alcohol, which dissolves the biliary resin. 

 On evaporating the alcoholic solution and treating the residue 

 with cold alcohol, we obtain a solution of biliary resin (fellinic 

 and cholinic acids, and dyslysin.) 



The portion unacted on by alcohol may still contain bili- 

 phsein and biliary mucus ; the former is soluble in carbonate of 

 ammonia, the latter in a solution of potash. 



Human gall-stones vary from the size of a hemp-seed to that 

 of a pigeon's egg; they are round, or, if several occur together, 

 angular and flat-sided, each facette lying in close apposition 

 with that of the adjacent calculus. Their surface is smooth, 



1 [For further information on this subject the reader is leferred to a paper by 

 Guibourt, in vol. 16 of the ' Comptes Rendus,' and to observations ' on a new organic 

 acid in benzoar stones,' by Lipowitz, in Simon's Beitrage, p. 462.] 



