340 OPERATIONS ON THE DIGESTIVE APPARATUS. 



tliis frame a solid blade with a sharp con- 

 cave edge turned backward. The other 

 extremity of this rod carries a transverse 

 prolongation, which serves to change the 

 position of the blade when necessary, and 

 which has on its shorter portion a hole 

 through which the other rod is allowed 

 to shde. This second rod has on one end 

 a sharp blade which slides into suitable 

 grooves made in the frame of the first, 

 and is curved forward on its front edge. 

 On the other extremity it carries a metal- 

 lic mass which is used as a hammer. 



In using this instrument, the tooth 

 being enclosed in the frame between the 

 two blades, the movable rod, with its sharp 

 edge, is pushed against the blade of the 

 frame, and a strong blow of the hammer 

 cuts off the tooth smoothly and evenly. 



The chisel invented by Gowing (Fig. 

 344), works somewhat on the same princi- 

 ple as that of Brogniez. 



Resection of the teeth has also been per- 

 formed with the instruments used for the 

 same operation on bones. Saws of various 

 form and design are also recommended, 

 the chain saw, which we have often used, 

 being one of these. But there are serious Fig.344— Gow- 

 objections to this latter instrument, among 

 which is its liabihty to become heated while in use, 

 when it becomes unable to " bite " upon the hard 

 dental substance, and may, moreover, break or slide. 

 The only method of overcoming these 

 objections, which, in fact, may occur 

 in using any kind of saw, is by hold- 

 ing a wet sponge against the tooth to 

 which the instrument is apjjlied — a 

 precaution which is not always of easy 

 adoption, and which can scarcely be 

 effected without more or less danger 

 of wounding the hand which holds 



Fir,. 34.3.— Brogniez's Tooth Chisel. 



