The dilatation is repeated at intervals of from eight to ten days, until, at the expiration of a month or six weeks, the amount of total expansion of the heels registers nearly an inch.  That the method requires the greatest care may be gathered from the reports of continental writers.  They state that frequently the pain and consequent lameness keep the patient confined to the stable for several days.

Numerous and but slightly differing forms of the dilator are on the market.  As in principle they are all essentially the same, and are to be found illustrated in any reliable instrument catalogue, they need no description here.

[Illustration:  FIG. 75.—­DE FAY’S VICE.]

(c) Hartmann’s.—­A further useful expansion shoe is that of Hartmann’s (Fig. 76), in that it may be adapted for either unilateral or bilateral contraction.  This shoe is also provided with bar-clips, and forcibly expanded at the heels by means of a dilator.  The expansion is governed by saw-cuts through the inner margin of the shoe directed towards its outer margin, and running only partially through the inner half of the web (see Fig. 76).

According as the contraction is confined to the inner or outer heel, the saw-cuts, one or two in number, are placed to the inner or outer side of the toe-clip.  When the contraction is bilateral, the saw-cuts, one or more in number, are placed on each side of the toe-clip.

(d) Broue’s.—­This is one of the forms of so-called ‘slipper’ shoes (see Fig. 77).  We have already indicated that the shape of the bearing surface of the ordinary shoe—­by its ‘seating’ or sloping from outside to inside—­is sometimes a cause of contraction.  In the ‘slipper’ of Broue this bearing is reversed, and the slope is from inside to outside.  In the original form of this shoe the slope to the outside was continued completely round the shoe.  Experience taught that the strain this enforced upon the junction of the wall with the sole was injurious, and that the ‘reversed seating,’ if we may so term it, was best confined to the hinder portions of the shoe’s branches.

[Illustration:  FIG. 76.  This figure illustrates the principle of the Hartmann expanding shoe. a, a, The clips to catch the inside of the bars; b, c, saw-cuts.]

The amount of slope should not be excessive.  If it is, too rapid and too forcible an expansion takes place, and pain and severe lameness results.  Dollar gives the requisite degree of incline by saying that the outer margin of the bearing surface of the shoe should be from 1/12 to 1/8 inch lower than the inner.

In the case of the Broue slipper, it is the animal’s own weight that brings about the widening of the heels, the slope or outward incline of the slipper simply causing the inferior edge of the wall at the heels to spread itself outwards instead of sliding inwards on the bearing surface of the shoe.

[Illustration:  FIG. 77.—­THE SLIPPER SHOE OF BROUE.]