538 
MR. B. CLARK S HIPPODONOMIA. 
This then is the sum of Mr. Bracy Clark’s discovery, that the 
foot is formed on an elastic principle, and that the resistance of 
the nails, by means of which the shoe is attached to the foot, 
prevents the developement of this principle, and entails on the 
foot various evils. 
We might object a little to the accuracy of Mr. B. Clark’s 
definition, if definition it be, of elasticity; or rather we object that 
there is no strict definition of the principle, no graphic descrip¬ 
tion of its application, or the disturbance of its application, but a 
great deal said prettily, and well, and yet loosely and uncon- 
nectedly, about it. Now we do object to this in a scientific 
work, and which is, and deservedly, the basis of the author’s 
fame. 
Elasticity is that principle by which the particles of bodies 
yield to a certain extent when force is applied, but immediately 
regain their natural position when the disturbing force is with¬ 
drawn. It is this latter part of the definition which consti¬ 
tutes the elasticity of the body ; the former is the mere partial 
disturbance, or separation of the parts. We see this principle 
most beautifully displayed in the foot of the horse. That organ is 
the very perfection of elasticity. The strength of the horny and 
the sensible lamellae is accurately adjusted to the weight which 
is thrown upon them; but when, in the action of the horse, some 
velocity is added to that weight, and the momentum or force which 
acts upon them is increased, they elongate—and in consequence 
of that elongation the coffin bone descends, and it presses upon 
the concave sole, and that yields ; and its arch becomes flattened, 
and, becoming flattened, requires a wider base, and the foot is 
expanded: and so when the frog, in the descent of the foot, re¬ 
ceives a certain degree of pressure, it acts upon the sensible frog 
which it covers, and squeezes it, or would squeeze it, into 
smaller compass ; but although soft and yielding, it is incom¬ 
pressible, and it resists downwards, and forces apart the con¬ 
cavities of the horny frog, and it rises upward and forces asunder 
the cartilages, and thus the expansion of the heel is assisted below, 
and produced above. This is an exquisite mechanism: the gradual 
resisting prolongation of the lamellae, and the gradual yielding and 
flattening of the arch of the sole, and to a lesser degree the gradual 
rising and pressure of the sensible frog, lessen and neutralize and 
destroy that concussion which must otherwise have been speedily 
ruinous to the animal, and expand the various parts of the foot. 
There is, however, nothing of elasticity here; it is the mere 
alteration of position. But now comes the true principle of elas¬ 
ticity, which Mr. Bracy Clark does not appear to have ob¬ 
served with perfect accuracy the power ceases to act; the 
weight of the horse no longer violently presses; and the lamellae 
