AN ESSAY ON CHRONIC PODOTROCHOLITIS. 33 
tebrse are endowed, and the binder ones especially, these bones 
also contribute their share in warding off shocks. 
If we weigh all these considerations, it will be evident that 
the fore extremities are distinguished from the hinder ones, setting 
aside the less flexibility of the pasterns, by an inferiority of power, 
by the distribution of the weight, and by the diminution of per- 
cussion. We must also take into account the head and chest, 
which, being inclined beyond the basis of support, draw the fore- 
legs from the centre of gravity, and oblige them, during the act of 
progression, to receive the impulsive power communicated to the 
machine by the hinder extremities : finally, the fore-feet actually 
support a greater degree of weight, although endowed with infe- 
rior means of opposing and multiplying re-actions. It would be 
superfluous to enter into any demonstration of the destructive in- 
fluence which such a disproportion must necessarily exercise over 
the whole of the limbs*, and especially upon the extremities of 
them, the feet. It increases the pressure and friction which the 
trochlea undergoes, and gives to the fore-feet a more decided 
predisposition to take on chronic podotrocholitis. 
The fore extremities, then, sustain shocks less easily, in conse- 
quence of the conformation of their upper parts ; but this defect is, 
in some degree, compensated by the great elasticity of the hoofs of 
the fore-feet, the walls of which diminish in thickness from the 
front backwards. This property, however, involves predisposition to 
various forms of hoof-bound ; and all causes liable to limit or anni- 
hilate the property of the sole and the frog to yield to pressure 
from above, tend to predispose to podotrocholitis, since they give 
rise to a compression of the tendon and the navicular bone. To 
these causes belong that partial contraction of the sole and frog 
spoken of by Turner and Goodwin. This kind of hoof-bound, 
which, as we have already stated, is characterised by the con- 
cavity, thickness, and hardness of the sole, by the contraction and 
hardness of the frog, by the depth and shrinking of its clefts, is 
generally accompanied by a total or partial contraction of the wall 
of the hoof. In the latter case, the dimensions of the hoof are so 
sensibly altered, that the superior transverse diameter exceeds that 
of the plantar surface; and the obliquity of the quarters is so great, 
that two imaginary lines drawn from the coronet, sufficiently pro- 
longed, would meet ; and, if a third transverse line were drawn 
from one side of the coronet to the other, uniting with the other 
* The considerations into which I am about to enter will also account for the 
more frequent occurrence of exostosis on the fore than on the hinder limbs. 
The Clinical and Chirurgical Journal of the lately suppressed Veterinary 
Institution at Wilna shews that, in sixty-eight cases of exostosis, sixty-five 
affected the fore- legs, and only three were found on the hinder ones. 
VOL. XX. F 
