EXPANSION OF THE HORSE’S FOOT. 
383 
upper and back parts of the heels, caused by the bending back of 
the os coronae on the elastic tissue at the heels, thus expanding the 
lateral cartilages; and that if the frog is brought into contact with 
the ground, it takes its share of duty, by its elasticity, in warding 
off concussion; also that the elastic periosteal tissue of the coffin- 
bone performs a most important part in warding off concussion, by 
allowing of a slight spring to the coffin-bone in every direction. 
3d. That in a horse in a state of nature, or shod with the heels 
sprung, a certain action of the foot goes on in addition ; namely, 
a slight declination of the whole hoof in the direction of its fibres: 
thus allowing the heels and base of the frog to descend, which I 
consider to be the natural action of the foot, and that by shoeing 
we prevent this natural backward and downward action. 
4th. That the descent of the base of the frog is entirely governed 
by the descent of the heels ; and that in ordinary shoeing the base 
of the frog is a fixture, putting this important organ greatly out of 
use; but that the slight descent of the frog and the adjacent parts 
of the sole, at the anterior part of the frog opposite to the navicular 
bone, takes place under all circumstances of shoeing. 
5th. That there is no appreciable descent of the horny sole, in 
moderately concave feet, under ordinary circumstances of shoeing, 
except perhaps of that part of it adjacent to the anterior part of 
the frog, opposite to the navicular bone, which very slightly yields; 
but that with a shoe sprung at the heels, or when a horse is in a 
state of nature, there is a yielding backwards and downwards of 
the horny sole, together with the whole horny box. 
6th. That there is not sufficient descent of the sensible sole upon 
the horny sole, under ordinary circumstances, to impede the cir¬ 
culation of blood in the foot, and that those beautiful provisions in 
the foot for the carrying on of the circulation seem to me rather 
designed to remove the possibility of obstruction to the course of 
the blood than as the general means by which that circulation is 
forced onwards. 
7th. That the laminse are nearly, if not altogether, inelastic; that 
they are very readily moved in their transverse direction, but not 
in their longitudinal direction; and that this movement of the 
laminae arises probably from the peculiar construction of the 
elastic periosteal covering of the coffin-bone admitting only of 
these peculiar motions. 
Believing these to be the principal points, I submit them to the 
careful consideration of the profession ; feeling reluctant to bring 
the subject forward from knowing that the opinions here expressed 
are contrary to those generally received as truths, and that the 
present doctrines of the physiology of the foot have been so long 
regarded as established facts, that the ideas expressed in this 
