318 
EXPERIMENTS ON THE 
under surface of the foot, lying evenly up to the heels, and to the 
coronet bone a piece of wood was fitted, which had a flat upper 
surface. Pressure was applied in a vice, the wood and the iron 
being the opposing surfaces. 
Result .—The crack closed immediately. 
Observations .—The crack closed in this case, shewing, as I con¬ 
ceive, that where yielding backwards of the horny box can take 
place, it will do so. If there had been no crack in the hoof, no 
yielding backwards could have taken place, as the hoof itself, rest¬ 
ing perfectly close on the shoe at the heels, must first be forced 
into the iron before this backward motion of the foot could be ac¬ 
commodated. In cases of sandcrack, where a shoe is applied 
which totally relieves that portion of the quarter of the foot poste¬ 
rior to the crack from pressure, we may remark, that the crack will 
visibly open considerably more when the horse is in motion than it 
would do if the shoe rested posterior to the crack; thus shewing 
that this backward action of the foot will go on if it is not pre¬ 
vented. 
1 6th Experiment. 
Subject, a cart-horse, with good feet, moderately concave. 
To the near fore foot a shoe was applied greatly sprung at both 
heels: this shoe had a thin bar of iron welded to each heel at its 
under surface, and lying across the shoe. 
Result .—As soon as the horse was made to stand upon this shoe, 
you could see a visible descent of the foot downwards and back¬ 
wards, and you could also feel it; and at every motion of the ani¬ 
mal this action of the hoof could be seen and felt. With a view 
of measuring this descent, the space between the iron bar and the 
frog was filled up with prepared wax (the upper surface of the 
iron bar having been first well oiled). The horse was now made 
to walk about, when I could perceive that the heels of the foot 
descended nearly to the heels of the shoe, and there was an imme¬ 
diate descent of the wax on the iron bar. On the foot being lifted, 
the heels resumed their natural position, and there was now a space 
between the wax and the iron of nearly one-fourth of an inch. 
1 6th Experiment. 
Subject the same. To the off fore foot a shoe was applied 
sprung at both heels, and on the horse standing on this shoe the 
same effects followed as in the preceding case. A small piece of 
iron was now made to fit the space at one heel where it was sprung, 
and it was pushed in to prevent this spring acting. 
