Examined on the foot, deprived of its horny covering, the sensitive laminae are, the majority of them, in close contact with each other.  In the normal state this is not so.  The interstices between the leaves are then occupied by the horny leaves, to be afterwards described as existing on the inner surface of the wall.

Reaching and rounding the heels, the sensitive laminae extend forward for a short distance, where they interleave with the horny laminae of the bars.

Much discussion has centred round the point as to whether or no the cells of the sensitive laminae take any share in the formation of the horn of the wall.  This will be alluded to in a future chapter.

I. THE HOOF.

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, outside toe; 4, the quarter; 5, entigeral groove; 6, horny laminae.]

For observation the wall offers two faces, two borders, and two extremities.