DISEASES OE THE LATERAL CARTILAGES 375 



( Smith's ). Fig. 146, or the hoof chisel ( Hodder's ), Fig. 147. 

 With the hoot 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 



Fig. 145.— Hoof Plane (Smith'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 



Fig. 147.— Hoof Chisel (Hodder'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 



