We have, then, in this condition, as we indicated at the commencement, but a phase in the evolution of ordinary contracted heels, for, with the progress of the contraction already existing at a, a, and below those points, it is only fair to assume that with it falling in of the at present bulging coronary margin must sooner or later occur, that, though expanded when compared with the wall below it, it will be really contracted as compared with what it was once in that same foot.

We may therefore conclude this section by remarking that factors tending to contraction of the heels in general are equally potent in the causation of contracted coronet alone.

Treatment.—­Exactly that described for contracted heels.  Bearing in mind that contracted coronary margin is but the onset of contracted heels, and that its first exciting cause is that of removal of the ground-pressure upon the frog, the most careful attention must be paid to the shoeing.  The use of bar shoes, ordinary frog pads, or heelless shoes and bar pads, are especially indicated, together with abundant exercise.  By these means the normal movements of expansion will be brought into play, and the condition quickly remedied.

C. FLAT-FOOT.

Definition.—­By this term is indicated a condition of the foot where the natural concavity of the sole is absent.

Symptoms.—­In the flat-foot the inferior edge of the wall, the sole, and the frog, all lie more or less in the same plane.  It is a condition observed far more frequently in fore than in hind limbs, and is seen in connection with low heels, more or less obliquity of the wall, and a tendency to contraction.  The action of the animal with flat feet is heavy, a result partly of the build of the foot, and partly of the tenderness that soon comes on through the liability of the sole to constant bruising.

[Illustration:  FIG. 80.  This figure represents the lower surface of a typical flat-foot.  It illustrates, too, the commencement of a condition we referred to in Section B of this chapter—­namely, the compression of the frog by the ingrowing heels (b) and bars (a).]

Causes.—­Flat-foot is undoubtedly a congenital defect, and is seen commonly in horses of a heavy, lymphatic type, and especially in those bred and reared on low, marshy lands.  It is thus a common condition of the fore-feet of the Lincolnshire shire.

As might be expected, a foot of this description is far more prone to suffer from the effects of shoeing than is the foot of normal shape, and regarded in this light shoeing may be looked upon as, if not an actual cause, certainly a means of aggravating the condition.  Directly the shoe—­or at any rate the ordinary shoe—­is applied, mischief commences.  The frog is raised from the ground, and the whole of the weight thrown on to the wall.  The heels, already weak and inclined to turn in, are