72 A NEW OPERATING CHAIR. 



effected by a few revolutions of a small handle 

 placed at the back of the chair. 



When operating upon lower incisor teeth, which 

 incline inward, the upright back will afford great 

 advantage over the inclined, by enabling the head 

 to be placed in such a position as that the direct 

 rays of light will fall on the posterior surfaces of 

 these teeth. The extreme horizontal position will 

 be favourable should the patient be overcome by 

 faintness. Some operators have found the horizontal 

 position desirable for stopping the posterior molars. 



The upward and downward movements of the 

 back of the chair serve to adjust its curve to that of 

 the spine ; by means of this movement also, in con- 

 junction with that of the seat, we may raise the 

 head to a much higher level than can be obtained 

 in the ordinary operating chair, thus enabling the 

 operator to stand or sit whilst operating. The back 

 of the chair can be raised five inches, by means of a 

 small handle placed behind and at the side of the 

 chair. 



Head-piece Movement, — Next to that of the seat, 

 perhaps, this will be found most frequently called 

 into requisition, owing to the numerous purposes to 

 which it may be made subservient, and also to the 

 facility with which it may be applied. 



The movement is obtained by detaching with the 

 pressure of the thumb a pin which secures the head- 

 piece by entering a perforated .segment plate ; the 

 head-piece can now be rotated freely, but upon 



