432 MORBID PRODUCTS. 



on the addition of hydrochloric acid to the aqueous solution, 

 crystals are separated, which dissolve readily in alcohol and 

 evolve an odour of benzoic acid. 



f. It is cholesterin if the concretion exhibits a crystalline 

 character, if the portion under examination burns with a bright 

 flame, if it dissolves in boiling alcohol, and separates from it on 

 cooling in crystalline plates or scales, and if it does not dissolve 

 in caustic potash. 



g. Biliary resin is a frequent constituent of biliary calculi, 

 but never occurs alone. It may be easily recognized by its so- 

 lubility in alcohol, by its extremely bitter taste, and by its 

 separation from its alcoholic solution on the cautious addition 

 of water. 



h. It is biliphsein if it has a brown or ochre-yellow colour, 

 if it evolves an animal odour on burning, if it is only slightly 

 soluble in alcohol and water, but freely in caustic potash, com- 

 municating to it a dark brown tint, and if the addition of nitric 

 acid to this solution causes the well-known change of colour. 



1. It is fibrin if it softens when heated on platinum foil and 

 evolves an odour of burnt horn, burning with a clear flame, and 

 leaving scarcely any residue; if it dissolves in caustic potash 

 from which it is precipitable by acetic acid, and finally, if it dis- 

 solves in an excess of acetic acid from which it is precipitable by 

 ferrocyanide of potassium. It must be remembered that this 

 description applies equally to albumen. 



k. Concretions containing hair may be known by their 

 light specific gravity, and by their appearance on making a 

 section. When burned they develop an odour of burned horn. 

 They dissolve in caustic potash, but in none of the other ordi- 

 nary solvents, 



2. If the portion submitted to examination becomes black 

 on the first application of heat, and only slightly diminishes, it 

 may consist of the earthy phosphates, carbonates, and oxalates, 

 or of the urates with fixed bases, for then the uric acid becomes 

 converted by heat into carbonic acid, and the bulk of the 

 specimen does not very perceptibly diminish. 



a. It is neutral phosphate of lime (which is not often the 

 sole constituent) if, when the heat is continued, it fuses, and 

 neither before nor afterwards effervesces with acids ; if it dis- 



