The shape of the bearing surface of the shoe is often to be blamed.  Where this is concave—­’seated’—­and the ‘seating’ is carried back to the heels, it is easy to see that, when weight is on the foot, there is an ever-present tendency for the bearing edge of the wall to slide down towards the inner edge of the shoe.  This tendency, operating on both the inner and outer wall simultaneously, must strongly favour contraction.

A further wrong practice is that of continuing the nailing too far towards the heels.  In our opinion this is not now often met with.  When it occurs its effect is, of course, to prevent those movements of expansion of the wall which we now know to be normal and most marked at the heels.

It may be remarked of the build of the shoe, or of errors in the preparation of the foot, that neither are of much moment.  Neither are they.  But when one stays to consider that errors of this description are practised not only once, but each time the horse goes to the forge, and that with some of them—­those relating to the build of the shoe—­the injury thereby brought about is inflicted not only once, but every day that particular shoe is worn, then it is not to be wondered at that, sooner or later, ill consequences more or less grave result.

Prognosis.—­This will depend to a very large extent upon the conformation of the limb, and upon the previous duration of the contraction.  Contraction of long standing, where atrophy of the sub-lying, soft structures and the pedal bone may be expected, will prove obstinate to treatment.  Especially will this be so if the lateral cartilages have become ossified.  Neither may we look for much benefit from treatment if the contraction has occurred in animals with an oblique foot axis and flat hoofs.

On the other hand, if the case is comparatively recent, if the limb is straight and the form of the hoof is upright, and if matters are uncomplicated by side-bones, or other serious alteration in the internal structures, then treatment may be rewarded with some measure of success.

[Illustration:  FIG. 63.—­TIP SHOE.  The dotted portions represent the length of the branches removed.]

Treatment.—­The greater part of the treatment of contracted foot will almost suggest itself as a corollary of the causes we have enumerated.  The normal width of the heels may be renewed, and development of the wasted frog brought about by one of three methods: 

1.  By restoring the pressure from below to the frog.

2.  By the use of an expansion shoe.

3.  By operative measures upon the horn of the wall.

1. By Restoring the Pressure from Below to the Frog.

This may be accomplished as follows: 

(a) By Shoeing with Tips.—­This method is advocated by Percival, by A.A.  Holcombe, D.V.S., Inspector.  Bureau of Animal Industry, U.S.A., by Dollar in his work on horseshoeing, and by many others.