In the case of the Broué 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.
FIG. 77.—THE SLIPPER SHOE OF BROUÉ.
(e) Einsiedel's.—Like the 'slipper' of Broué, the Einsiedel shoe depends for its effects upon the slope of the bearing surface.
It differs from the Broué 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 Broué, 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.
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.