s the use of special instruments, but who, at
the same time, do not care to use the saw, will find their wants supplied
in the hoof plane (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.

[Illustration: FIG. 146.--HOOF PLANE (SMITH'S).]

When using the knife or the hoof plane it is not often 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.

[Illustration: FIG. 147.--HOOF CHISEL (HODDER'S).]

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 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 feet so much of the wall is isolated at the
bottom that insufficient is left to nail the shoe to.

The next line to be made is the rear one. Its correct position is
ascertained by first noting the junction off the wall with the bar (see
groove 2, Fig. 149); and its inferior end must be just anterior to the
inflexion of the wall. This is done that we may avoid cutting the bar. The
position of the lower end of the rear line thus ascertained, it is run
upwards with the chalk in the direction of the horn fibres.

[Illustration: FIG. 148.--DIAGRAM ILLUSTRATING THE POSITION OF THE GROOVES
IN THE WALL IN COLONEL SMITH'S OPERATION FOR SIDE-BONE. 1,2, and 3, mark
the grooves in the order in which they are made; the dotted line _a_ marks
the position taken by the anterior line when the side-bone, is one reachi