ON THE DISEASES OF THE TEETH OF THE HORSE. 635 
screwed down upon the cylinder, thereby causing the packing 
to be so compressed as to retain the rod of the chisel in its de- 
sired situation. The mode of operating with this instrument 
will require some explanation from me, for I have been asked 
by some gentlemen whether the chisel is to be drawn back to 
the utmost range of the guard 1 I mention this, that others may 
not fall into the same error ; for if it were so placed before the 
chisel reached the tooth, the force of the blow would be expended 
to a great extent, on account of the distance it would have to 
travel and the resistance it would naturally have to overcome. 
For these reasons we should, probably, be foiled in the perform- 
ance of that which we were desirous of accomplishing, and the 
tooth would, in all likelihood, remain entire. 
After a due examination of the mouth has been made, and we 
have selected the tooth to be operated upon, the animal should 
be restrained by means of a twitch, and a balling-iron ought 
then to be placed in the mouth. The common open balling-iron 
will answer the purpose, but the one I would recommend you to 
use is that invented by Mr. Varnell. It has a shifting bar, which 
is regulated by a screw nut at the bottom, that allows of its being 
readily adapted to any sized patient. And, for a better pro- 
tection to the mouth of the horse, Mr. Varnell has caused the 
bars of his instrument to he covered with vulcanized Indian 
rubber. 
The balling-iron being retained in its situation by an assist- 
ant, the chisel is to be drawn sufficiently back through the cy- 
linder to allow the frame to be placed over the tooth, surround- 
ing that portion we are desirous of removing. This will be 
better accomplished by the operator grasping the cylinder firmly 
close to the brass bulb, at the same time employing so much 
traction as will suffice to keep the chisel at the posterior part of 
the frame close to the back of the tooth. The tooth being closed 
in, laterally by the guards and posteriorly by the passive chisel, 
the active chisel is then to be brought in contact with the an- 
terior part of the tooth. It will thus be seen that the tooth is 
imprisoned on all sides, and a hammer of about two and-a-half 
pounds weight is to be selected to give the blow with. The or- 
dinary smith’s hammer will answer if of sufficient weight, should 
expense be a consideration; though I think, as a general rule, 
perfect instruments will pay for themselves in the lung run , by 
a saving of much time and trouble, and also by causing us to be 
properly esteemed by our employers. 
Having grasped the cylinder in the manner before described, 
a sharp blow is now to be given to the button or head of the 
chisel. But division of the tooth will not lake place always at 
the first percussive action of the hammer. The blow will some- 
