BILIAEY CALCULI. 93 



acid. In this solution water produces an orange- 

 coloured deposit. Neither cholesterine, nor bilifuscine, 

 nor bilirubine, can be extracted from them, but they 

 contain besides the coloured peculiar ingredient much 

 earthy salt. They constitute the variety known as 

 calculi with prevalence of modified cholo chrome, and are 

 found in old and decrepit persons. 



5. Heat a portion of the calculus, it evolves the 

 odour of burnt feathers, and on combustion leaves a 

 slight ash. Treat a portion with alcohol and a little 

 sulphuric acid, and observe its solution in the alcohol. 

 Treat a portion of the calculus, or of the alcoholic 

 extract with sulphuric acid and sugar as directed under 

 cholic acid, a violet colour is produced. These 

 reactions characterise calculi with prevalence of biliary 

 acids. 



6. Heat a portion of the calculus and it will evolve 

 an odour of burning fat. Treat a portion with acetic 

 acid and boiling alcohol and it will dissolve, and on 

 cooling deposit fatty acids. Determine the melting- 

 point of these, and test their reaction with a boiling 

 solution of phosphate of sodium. The calculus may 

 contain biliary pigments : Calculi with prevalence of 

 fatty acids. 



7. Heat the calculus or a portion and observe that it 

 is merely coloured, hardly contains organic matter, and 

 that its ash almost retains the shape of the matter 

 before heating. Add hydrochloric acid to the ash, or 

 to the original calculus, and it will dissolve with effer- 

 vescence. Over-saturate the solution with ammonia 

 and no, or scarcely any, precipitate will ensue. Such 



