On a new application of Lever Power, fyc. 201 



ments, and many of their important discoveries in anatomy 

 and physiology, in the valuable papers which they read 

 before the Royal Society of London. 



During my early residence in Melbourne I had fre- 

 quent occasion to extract teeth, and have therefore some 

 practical knowledge of the difficulties that are sometimes 

 experienced. The chief difficulty is met with in the case of 

 the inferior molar teeth, and I have seen the strongest efforts 

 sometimes fail in extracting them. On two occasions the 

 common key broke in my own hands, from the force re- 

 quired to be used. 



The key, however, is not by any means a perfect instru- 

 ment, as the extracting force is not applied in the axis of 

 the tooth, but at a««considerable lateral angle, and therefore 

 at a great disadvantage. On this account the forceps is now 

 preferred by surgeons and dentists; but this instrument, 

 especially in the case of the molar teeth, requires peculiar 

 skill, and strength of wrist which very few possess, and the 

 operation of extraction with the forceps is often much more 

 formidable and much more painful than with the key. 



I shall now simply apply the key to one of the inferior molar 

 teeth, and you will see at once that the lever power em- 

 ployed is very far from being in the axis of the tooth, and 

 that there is even considerable danger of the tooth being 

 broken across, and of the jaw itself being injured, when 

 much force is used. I may dismiss the key, however, as it 

 is now almost abandoned by dentists, and direct your atten- 

 tion to the forceps. 



This instrument has been used in various forms, some of 

 which are exhibited, but of these it is unnecessary to speak. 

 In all the intention is that the extracting force should be 

 applied in a line with the axis of the tooth ; and when long 

 practice has given unusual skill, and extraordinary strength 

 of wrist to the operator, the forceps may be regarded as in 

 many respects a perfect instrument. It is impossible, 

 however, to deny that the forceps is not and cannot be used 

 by most operators in this skilful and powerful manner ; and, 

 in point of fact, it is almost always used in the first instance, 

 to shake the tooth from side to side, and to twist it in its 

 socket before the extracting force is applied ; and without 

 great skill and great strength, many teeth cannot be ex- 

 tracted by the direct application of power in a line with the 

 axis of the tooth. 



Thus, with all the advantages of daily practice, I have 

 b b" 



