THE POWER OF THE TOHGtfE. 157 



impossible to dilate the mouth sufficiently to slide the 

 instrument between it and the corresponding lower 

 tooth. Besides, the tongue, however firmly it may be 

 held outside the mouth, has still the power to displace 

 the instrument by the energy of the undulatory move- 

 ments at its base. Again, the back grinders, having 

 ordinarily" shorter bodies than the others, afford less 

 hold for the instrument. In some cases they afford no 

 hold at all, as their bodies are worn almost to a level 

 with the gums. 



" Lastly, in some cases the exostosis of the root of 

 the tooth is so great that it is, as it were, wedged in 

 the socket, and resists all efforts to extract it. What 

 is to be done ? The disease may lead to grave local 

 complications and dangerous general disorders. In 

 such a case we would recommend trephining the dis- 

 eased sinus and punching the tooth into the mouth. 

 This operation being very unusual, and the observance 

 of some rules requisite for practicing it, we will con- 

 sider it somewhat in detail. 



" If, as sometimes happens, the swelling over the 

 sinus is indistinct, it would be well to be gurded by a 

 prepared head, in order to apply the trephine in the 

 exact place, which is above the diseased root. A large 

 V or crucial incision should be made, and the trephine 

 manipulated till the sinus is laid open. The opening 

 should be extensive rather than confined; it is more 

 convenient to apply upon the parietes of the sinuses 

 three crowns of the trephine, tangent reciprocally at 

 their circumferences ; then, by the aid of a sharp in- 

 strument and a small hammer, the angles may be re- 

 moved. 



"As soon as the mucous membrane of the cavity has 

 been laid bare, the change it has undergone may be 



