ANATOMY AND PHYSIOLOGY OP THE HOUSERS FOOT. 143 
essential structures of the horse’s foot, to a sock ; the hoof 
stands in the same relation to these that a boot or shoe does 
to the human foot encased in its covering of silk, cotton, or 
woollen. It is a thick, hard, and insensible (or non-vital) 
case of fibrous horn, accurately adapted to and moulded on 
the superficies of the parts it contains and protects, and to 
whose external configuration it owes its form. It has its 
analogies, in other animals, in the thickened epidermis, pads, 
nails, claws, &c., with which their feet are provided. 
In order to study it properly, it is necessary to remove it 
from the foot by maceration in water ; and further macera- 
tion, by separating it into its different constituent parts, 
permits a detailed study to be made of these. 
Viewed as a whole, either before or after removal from the 
foot, or even after prolonged maceration has disunited its 
component divisions, what we would call a well-shaped hoof 
is cylindro-conical in form ; or, as it has been otherwise 
defined, it has the figure of a truncated cone intersected at 
the base and summit of its axis by two oblique planes, the 
inferior of which converges rapidly towards the superior, and 
leaves this frustrum of the cone much higher in front than 
behind. In this respect the hoof corresponds to the os pedis, 
and its base or lower circumference is consequently larger 
than its summit, in accordance with its slightly conical 
figure. 
But though, in general terms, the hoof may be described as 
having this geometrical outline, strictly speaking it does not 
offer such a degree of regularity in form, its lower border 
being nearly always more circular and salient on the outside 
than the inside. 
And though, to the ordinary observer, the hoof appears to 
consist of one entire or indivisible case, intended by nature 
to protect the internal parts from contact with the ground 
and the influence of extreme cold or heat, yet, as has just been 
said, long maceration resolves it into three principal portions, 
which have received different names. These are the “ wall ” 
or “ crust,” the “ sole,” and the “ frog,” with its circular 
continuation, the “ periople.” 
Each of these parts we will examine somewhat carefully, as 
a knowledge of their structure, relations, and uses is of the 
utmost importance with a view to perfecting the farrier’s art. 
Our description will more immediately refer to the hoof of 
the fore extremity. 
The wall of the hoof . — The “ wall ” or “ crust ” of the 
hoof (garoi or muraille of the French, hornwancl of the 
Germans) is that portion we see in front and laterally when 
