634 ON THE DISEASES OF THE TEETH OF THE HORSE. 
The next thing that I beg leave to draw your attention to, is 
the elongation of a tooth. Sometimes the tooth will grow to 
such an extent that it projects considerably above the other 
molars. Now this is produced by the want of resistance of the 
opposing tooth, death of which has taken place, and loss of sub- 
stance has naturally resulted from the absence of that power of 
self-preservation natural to living structures; therefore it has 
no power to meet by growth the opposite tooth, and consequently 
the attrition necessary to keep those teeth on an acting level is 
lost. This overgrowth of the tooth has been for some time past 
a difficulty to remove, through the want of a proper instrument. 
The tools usually employed have been the ordinary smith’s 
hammer and chisel, rude instruments for such a purpose, while 
their use is not unattended with danger ; for, the shock being re- 
ceived upon the posterior tooth, this it must be self-evident would 
have a tendency to produce disease, and perhaps even a more 
serious injury. For the same purpose the saw has also been 
used, but it has proved alike ineffectual ; for who, having toiled 
with a saw, rubbing against the hard enamel of a horse’s molar, 
making little or no impression, has not wished for an improve- 
ment in his instrument] To meet those difficulties, I have in- 
vented this which I now exhibit to you, designated by me the 
Dental Sliding Chisel ( see fig. 2). It consists of a cylin- 
drical tube, which is attached to a guarded frame with an op- 
posing or cutting chisel at the extremity, so placed as to receive 
the concussion ; so that when the working chisel is struck, it 
prevents the shock from being felt or sustained by the posterior 
teeth. The acting chisel, as you perceive, moves within the cy- 
lindrical tube which forms the handle, the cutting part of it being 
guarded and protected by the frame of which I have spoken. 
The round part of the chisel plays or works through the cylinder, 
and to it is attached a steel head or button for the receiving of 
the blow or force necessary to be given. When we desire that 
it should cut through the hard and solid tooth of the horse, it 
will be seen that the rod of the chisel, working through the cy- 
linder, would fall from any situation in which it might be adjusted, 
on account of ihe elevated and standing position in which the 
animal’s head would necessarily be held by the operator. To 
guard against the chisel slipping backwards, and to render it 
steady, but not fixed, I have attached, as you will perceive, at 
this end of the cylinder a brass bulb, which gives to the hand- 
hold of the operator more security. The inside of the brass 
bulb, first mentioned, is hollow, so as to allow of some packing 
being placed within : when pressing upon the rod of the chisel, 
it acts on the same principle as it does in the piston box of a 
steam engine. To make this more clear, the brass bulb is 
