Removed from the foot by maceration a well-shaped hoof is cylindro-conical
in form, and appears to the ordinary observer to consist of a box or case
cast in one single piece of horn. Prolonged maceration, however, will show
that the apparently single piece is divisible into three. These are known
as (1) THE WALL, (2) THE SOLE, and (3) THE FROG. In addition to these, we
have also an appendage or circular continuation of the frog named (4) THE
PERIOPLE, or CORONARY FROG BAND. These various divisions we will study
separately.

1. THE WALL is that portion of the hoof seen in front and laterally when
the horse's foot is on the ground. Posteriorly, instead of being continued
round the heels to complete the circle, its extremities become suddenly
inflected downwards, forwards, and inwards. These inflections can only be
seen with the foot lifted from the floor, and form the so-called _Bars_. It
will be noticed, too, with the foot lifted, that the wall projects beyond
the level of the other structures of the plantar surface, taking upon
itself the bearing of the greatest part of the animal's weight.

The horn of the wall, viewed immediately from the front, is known as the
_Toe_, which again is distinguished as _Outside Toe_ or _Inside Toe_,
according as the horn to its inner or outer aspect is indicated. The
remainder of the external face of the wall, that running back to the heels,
is designated the _Quarters_.

In the middle region of the toe, the wall following the angle of the bones
is greatly oblique. This obliquity decreases as the quarters are reached,
until on reaching the heels the wall is nearly upright.

[Illustration: FIG. 19.--THE WALL OF THE HOOF. 1, The toe; 2, inner toe; 3,