thinned as we have described is this: the pared frog, lessened in volume,
does not meet the ground. It therefore fails to expand laterally with
weight, and cannot assist, as normally it should, in aiding the heels
generally in their movements of expansion. The weakened bars and the
thinned sole, meeting with no opposition from the frog, give downwards and
inwards with the body-weight at the precise moment these movements should
be directed mainly outwards. As a further result of non-resistance on the
part of the frog, this time in a lateral direction, the bars, the sole, and
the wall at the heels all contract at the exact time they should expand.
The end result must mean abnormal pressure and bruising of the sensitive
structures in that particular region. Naturally, also, the excessive
thinning of the horn renders direct injury to the sole from stones or other
objects in the road far more probable.

For this one reason alone--the manner in which it favours the production of
corn--too great a condemnation cannot be placed upon excessive paring of
the sole, the bars, and the frog.

When corns are already present, as they may be from other causes, the same
remarks will again apply to excessive paring. It is the custom with many
smiths to carefully pare down the discoloured horn in every case of corn
they meet with, and at the same time to again weaken the bars and even part
of the wall at the heels, with the laudable idea of relieving pressure on
the part diseased. After what has gone before, we need hardly say that
their well-meant efforts have a precisely opposite effect to the one they
intend.

The fitting of the shoe is, perhaps, to a greater extent responsible for
the causation of corn than is the paring we have just described.

A few of the evils connected with the shoe may, however, be justly
described as unavoidable. We _must_ shoe; we cannot shoe and leave a normal
foot!

A shoe excessively seated, especially from the last nail-hole backwards,
may be regarded as dangerous. In this case, with every application of the
body-weight, there is given to the foot a tendency to contract, especially
at its lower margin. Result: undue pressure upon the tissues around and the
production of corn.

On the other hand, varying with the form of foot, the seating may be
insufficient. In the case of flat-foot, or dropped sole, for instance,
insufficient seating will lead to undue pressure of the web of the shoe
upon the sole,