on the sensitive
laminae again diminished, and the lameness relieved.

Not that we are attempting to defend the operation--far from it. We simply
mention it as interesting, and quote this and the use of the bar shoe (with
both of which methods older operators have claimed success) merely as
evidence that the operation of Smith is based on a logical foundation.

When treatment is decided on, therefore, we may first advise blistering and
the use of a bar shoe. After that, should the lameness continue, and should
we still judge the side-bone to be the cause of it, the operation may be
advised.

As we have said before, the operation consists in so grooving the wall as
to allow of the quarters widening sufficiently to relieve pressure on
the parts within. In one or two previous portions of this work we have
considered operations involving this procedure. Before detailing the
operation here, therefore, we will first describe the instruments
necessary, and the most satisfactory methods of incising the horn.

To begin with, it must be remembered that all methods of hoof section have
for their object the after-expansion of the horny box, and that this can
only be brought about by making each groove complete from coronary margin
to solar edge of the wall, and carrying it, throughout its length, _deep
enough to reach the commencement of the sensitive structures_.

To this end, therefore, the operator must bear in mind the comparative
thickness of the various parts of the wall, and must, in particular,
remember the relative thinness of that portion of horn forming the outer
boundary of the cutigeral groove, and accommodating the coronary cushion.

For the making of the incisions there is the special saw devised for this
operation by Colonel F. Smith, A.V.D., and which we illustrate in Fig. 144.
With this the wall is sawn through _until the depth arrived at is equal to
what is indicated by a previous examination of the thickness of the crust
as viewed from the solar surface_. Here Colonel Smith says: 'I strongly
advise everyone to use a metal gauge (a thin piece of material) to
introduce into the incision made by the saw, and run it up and down to
ascertain whether the wall is properly divided throughout. The depth to
which this should be done we know from the previous measurements of our
gauge on the crust.'

[Illustration: FIG. 144.--SMITH'S SIDE-BONE SAW (EARLY PATTERN).]

Should the saw be of a pattern in which the set of