ng
far forward, while the dotted lines _b_ and _c_ mark the position of the
additional grooves to be made if thought necessary.]

The third line is made in such a position as to divide into two equal
portions the wall between lines 1 and 2. Here, however, some operators
prefer to make two, or even three, lines, adding those as at _b_ and
_c_, Fig. 148; and Smith himself says that a multiplicity of lines is an
advantage rather than not.

In any case, having once determined the position of the lines, they should
be plainly marked out with chalk, and then viewed from a distance with
the foot on the ground, in order to judge of their regularity. If we are
satisfied with them, we then lightly mark them with the saw, with the hot
iron, or with the knife, whichever instrument we may be intending to use.

Unless the details are methodically carried out as here described, it is
probable that more of the foot will be isolated than is necessary, and that
as a consequence very little is left to which to nail the shoe.

[Illustration: FIG. 149.--DIAGRAM ILLUSTRATING THE POSITION OF THE GROOVES
MADE IN THE HOOF IN COLONEL SMITH'S OPERATION FOR SIDE-BONES. 1, 2, and 3,
show the grooves in the wall in the order in which they are made; 4 shows
the groove made at the junction of the sole with the wall.]

The incisions are then made with the saw or the knife, with the foot
held in a convenient position by an assistant. That usually found most
comfortable for the first incision is with the foot held forwards and
placed on an assistant's thigh in the position adopted for 'clenching up'
when shoeing, while that for the rear incision is with the animal's knee
flexed, and the foot held well up to the elbow. In this, however, each
operator will suit himself.

Should the preliminary steps in making the incisions be performed with the
iron, it will be easiest done with the foot on the ground.

When the incisions through the wall are complete, our attention must be
given to the sole. A drawing-knife is here used, and a further incision
made over the white line so as to destroy the union of the sole with the
wall between incisions 1 and 2, and so completely isolate the portions of
wall included within the four grooves (see groove 4, Fig. 149). When this
is done it should be found that the portions of the isolated wall spring
readily to pressure of the thumb.

The inferior or wearing margin of the isolated wall must now be so trimmed
that it