THE FOOT. 449° 
tion of the structure itself. The horny case is attached to the foot by a 
delicate membrane, which lies in folds upon the pedal bone, and it can be 
torn away by violence, or when putrefaction has commenced, with great 
ease. These parts are here separately displayed. The several parts which 
we shall have to examine, commencing from without, are—1l. The horny 
case or hoof; 2. The parts which secrete it ; 3. The arteries which supply 
it with blood; and 4. The pedal bone and cartilages, as well as the 
navicular bone, which it encases. 
THE HOOF consists of three distinct parts, which, though in the recent 
state they are inseparably united, may be readily separated after maceration 
forafew days. These are the external wall or crust, the sole or slightly 
concave surface forming the bottom or floor of the case, and the triangular 
central portion of this called the frog. The crust reaches from the edge 
of the hairy skin to the ground, and averages about three inches and a half 
Fic. 3.—TuHe Hoor. Fic. 4.—Front View oF THE Fig: 5-—THE UNDER SURFACE 
A. Outer surface of crust. HOOT Ure aH POURS RES OF THE Foor. 
B. Inner surface of crust. . A. Cleft of frog. 
C. Upper surface of sole. A. Coronary substance. B. B. Sole. 
D. Part corresponding with the 3B. Lamine. C. Cleft between heels. 
cleft of the frog. 
BE. Coronary band. 
in depth. The front is the toe, the back the heel, and the intermediate 
part the quarter on each side. It is said by Bracy Clark to be a segment 
of a cylinder, but it is really narrower at the top than at the bottom, and 
it should rather be described as a section of a truncated cone. When 
examined from the side, the anterior surface should form an angle of 
about forty-five degrees with the line of the sole, and the upper edge or 
coronary band should join the sole, so as to leave a moderate substance at 
the heel; for if too great the foot does not expand, and is liable to disease 
from that cause; or if too thin and narrow, the foot is weak and gives way 
downwards, ending in a convexity of the sole instead of the reverse. Tho 
front of the crust is rather more than half an inch in thickness, and in a 
strong foot of average size gradually diminishing to the quarters, at the 
back of which it is generally barely a quarter of an inch thick, especially 
at the inner of the two. ‘This proportion is however confined to the fore 
foot, for in the hind there is little difference between the toe and quarters 
:n point of thickness. The superior border, or coronary band, is marked 
by its whitish colour. On its external surface it resembles the crust 
below; but internally it differs in being smoothly excavated, whilst the 
crust exhibits perpendicular striz, corresponding with the lamine; but 
this is not well shown in Fig. 3. In examining the cut of the sole, Fig. 5, 
it will be seen that the crust is bent inwards towards the frog at the heel 
GG 
