he double screw (_g_, _h_)
revolved by means of the wrench (k), until the opening of the jaws thus
obtained registers an expansion of 1/12 to 1/8 inch.

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