DISEASES OF THE LATERAL CARTILAGES 375 
(Smith’s), Fig. 146, or the hoof chisel (Hodder’s), Fig. 147. 
With the hoof plane the groove in the wall is made by a 
succession of downward scraping movements, while with 
the chisel the cut in the wall is made either from below 
upwards, or from above downwards, according as the foot 
is held forward or backward—whichever, in fact, comes 
most convenient. 
When using the knife or the hoof plane it is not often 
Fic. 146.—Hoor Prane (Smirn’s). 
that the sensitive structures are injured. In all cases, 
however, no matter what the instrument used, the metal 
gauge should be employed when the sensitive structures 
have been touched, and the operation obscured by blood. 
Our instruments at hand, the operation may be proceeded 
with. The first step is to ascertain the extent of the side- 
bone, and to determine the position of the incisions. To do 
this the coronet is felt with the thumb, and the anterior 
nny 
Se 
Fic. 147.—Hoor CuiseLn (Hopper’s). 
extremity of the side-bone noted. This is marked on the 
horn with a piece of chalk, and a vertical line dropped from 
this position to the inferior margin of the wall (Fig. 148, 1). 
The line crosses the horn fibres obliquely, and is purposely 
made in that direction in order that its inferior end may be 
far enough back to avoid the last nail-hole. Should the 
side-bone reach very far forwards, it may be wise to cause 
this line to slant from before backwards (see dotted line a, 
Fig. 148). Unless this is done, it is found that in some 
