ON GUTTA-PERCHA AS A PERMANENT STOPPING. 149 



a week or ten days. The chloroform dissolves out 

 the gutta-percha, leaving nearly the whole of the 

 colouring matter behind in th§ bag. When the 

 liquid is poured off, a second portion of chloroform 

 may be added, and the bottle set aside for a week 

 or two longer ; the whole of the soluble matter will 

 then be extracted. The solution is then placed in 

 a bottle with a small aperture near the bottom 

 closed with a plug, a small quantity of water added 

 to it, the whole well shaken up together, and set 

 aside for some days ; the water causes a slight 

 separation of gutta-percha in a flocculent state, 

 which gradually rises to the top,- carrying with it 

 the small portion of opaque insoluble matter which 

 had found its way through the pores of the bag ; 

 the clear liquid may then be drawn off from the 

 bottom, leaving the scum behind. The chloroform 

 is distilled off by a simple apparatus and preserved ; 

 and the gutta-percha, after remaining an hour or 

 two in an open vessel at about the temperature of 

 boiling water, to drive off the remains of the chlo- 

 roform, is then rolled out on a warm slab into a 

 thin sheet. 



With regard to the material to be mixed with the 

 gutta-percha, I was for a long time at fault. I 

 thought at once of pure silica, as likely to possess 

 the desired qualities, but nowhere could I procure 

 any that was of a pure white colour, or in impal- 

 pable powder ; every specimen that I tried proved a 



