68 
EXPERIMENTS ON THE FOOT OF THE HORSE. 
Secondly. That there takes place, during action, a measurable 
degree of lateral expansion around the quarters and heels at the 
circumferent border of the crust. 
One circumstance Mr. Gloag’s experiments strikingly demon- 
strate, viz. that when the point of bearing is removed from under 
the heels only, as in the case of a “ shoe much sprung at the heels,” 
the superincumbent weight is sufficiently great upon the hinder 
portions of the foot to bend even the fibres of the horn ; and this 
result of his experiments Mr. Gloag has considered to be “ the 
natural action,” and that whereby those indentations upon the old 
shoe were caused ; and it is to provide for this action that he re- 
commends his peculiar style of shoeing. 
But having shewn, by experiment, that no such action takes 
place when the foot is perfectly unfettered, we may conclude that 
Mr. Gloag was deceived by the illusive effect produced by placing 
the horse’s foot in an unnatural position ; and from hence inferring 
the great amount of weight that it is designed the hinder portion 
of the foot should support to the relief both of ligament and ten- 
don, we may form some estimate of the danger of depriving it of 
those adequate means of support which unerring Nature has so 
amply provided. 
But as there is little merit in quarrelling with a theory unless 
one has something to offer in return, I beg further to observe, that, 
with respect to the aforementioned depressions upon the heels of 
old shoes, I have been led to speculate an opinion myself, from 
having the circumstance forcibly brought under my notice whilst 
carrying out certain details connected with the application of vul- 
canized India-rubber. The descending heels, at first, nearly con- 
quered my ingenuity ; but this inconvenience having been over- 
come, I had a little leisure to consider its cause. 
I had ever considered the inequalities at the under and poste- 
rior part of the foot principally designed to give security to the 
footing ; the whole to form a natural “ break,” by which the animal 
could arrest his flight when in full career, or save himself when in 
danger of slipping. 
This instrument of safety consists of the two angular inflexions 
of the crust (which are both hard and sharp, and, in the well-grown 
foot, descend slightly below the level of the frog), first entering the 
ground, and forming two lateral holdfasts; the vomer-like frog, 
and concavities of the commissures. 
As this apparatus is placed posteriorly, we may very rationally 
conclude that the horse, upon the least danger, would instinctively 
have recourse to the hinder part of his foot, throwing the weight 
where it would be of most service. And how often in a state of 
domestication, especially upon our paved and wooden roads, has 
