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.]

_(e) Einsiedel's_.--Like the 'slipper' of Broue, the Einsiedel shoe depends
for its effects upon the slope of the bearing surface.

It differs from the Broue in being provided with a 'bar-clip.' This, in
addition to gripping the bars like the bar-clips of other expanding
shoes, also assists, under the body-weight, in expanding the heels by the
pronounced slope given to its upper surface. The expanding force exerted
by the body-weight falls thus, through the medium of the bar-clip, clip,
_partly_ upon the bars, instead of, as in the Broue, solely upon the wall.
We say _partly_ advisedly, for, in addition to the slope upon the outer
side of the bar-clips, the bearing surface of the heels of the shoe is
_slightly_ sloped outwards also. The good office served by the bar-clip is
the lessening of any tendency to strain upon the white line.

[Illustration: FIG. 78.--THE SLIPPER AND BAR-CLIP SHOE OF EINSIEDEL.]

Those we have described by no means exhaust the number of expansion shoes
that have been devised. There are numerous others, many of which are
composed of three-hinged portions, the two hindermost of which are
gradually separated by a toothed arrangement of their inner margins and
a travelling bar, the disadvantage of which is that it is liable to work
loose. In the majority of this class of shoe the hinges are placed far
forward, one on each side of the toe. They there become exposed to
excessive wear. In fact, against the bulk of this form of shoe it may
be urged that they cannot be worn by the animal at work, that they are
expensive, difficult to make, and easily put out of order.

3. _By Operations on the Horn of the Wall_.

_(a) Thinning the Wall in the Region of the Quarters_.--This is best
done by means of an ordinary farrier's rasp. The thinning should lessen
gradually from the heel for 2-1/2 to 3 inches in