182 EFFECT OF PRESSURE ON THE FEET OF HORSES. 
the crust, and expanding the crust on either side the toe, is 
entirely overlooked , on the supposition that it expands the heels 
only. 
The late Professor Coleman also considered that the sole de¬ 
scended, particularly at the heels, or corn places; that is, he 
begged the question in heavy horses; for in light horses he 
knew, as an anatomist, that it was an impossibility; therefore 
expansion of the heels could not happen in this manner. Now, 
Sir, I believe these to be mere errors of description. We 
should be thankful to these talented gentlemen for the know¬ 
ledge we derived from them ; but surely there is no reason why 
inquiring minds, like Mr. Gloag’s and others, should be pre¬ 
vented by these supposed axioms from better explaining the 
physiology of the foot, if they can do so, when they practically 
know that in many horses’ fore feet even there is not the least 
inclination to spread or increase the base. 
I doubt not that certitude has resulted from the experiments 
of others. I would not even deny the description of facts, but 
endeavour to trace out the causes. Mathematical certainty 
would give only the same results, under similar varieties and 
states of the foot. For instance, the proof of the rule given by 
Mr. Reeve is “ the hypothenuse given, to find the base and 
perpendicular.” Half the width of the hoof gives the length of 
the longest laminae, and one-sixth and a half of this half width, 
the depth of the coronary concavity at the toe, and the length 
of the laminae and depth of coronary concavity at the heels is 
one-fourth that of the toe. Now, the weight of the horse is 
supported by these, and the pressure is, therefore, in the ratio 
of four at the toe to one at the heels. In a hoof five inches 
wide the longest laminae, &c. or the hypothenuse is three inches, 
one-tenth the shortest, ,7|. The descent of the hypothenuse is 
,3 of an inch, and the increase of the base thereby is 
,1 of an inch. The lengths of the intermediate ones are found 
by the rule of proportion ; thus, the hypothenuse half the length 
is one inch, five and a half tenths causes by descent of the hypo¬ 
thenuse one and a half tenth of an inch, an increase of the base of 
one-twentieth of an inch ; but here, in the proper position of the 
foot, i. e. at thirty-five degrees from the perpendicular, and the 
base of the sensible foot, eighty-two degrees from it, horizontal 
expansion or shelving of the crust ceases at the outer part of a 
near or off fore hoof; whereas the same part at the inner side 
of the toe does not expand or increase the base, although it has, 
from being more under the centre of gravity falling between 
the fore legs, most pressure of weight. Instead of which, the 
frog either descends alone, or the upper edges of the bars also, 
while the lower edges are seen shelving outwards ; excepting 
