the fetlock, contraction in the anterior and lateral regions is slight, but
the expansion behind, in the region of the heels, is distinct, commencing
gradually in front, becoming stronger, and diminishing again posteriorly.
The coronary edge of the heels becomes slightly bulged outwards. The bulbs
of the heels swell up and incline a little backwards and downwards.

When the fetlock is raised the expansion of the coronary edge of the heels
disappears from behind forwards, passing forwards like a fluid wave. In
the lateral and anterior regions of the coronary edge the contraction
disappears; and when the weight is thrown off the foot it passes into a
gentle expansion of the coronary edge of the toe. During the opposite
movement of the fetlock, that of sinking backwards, this change of form is
executed in the converse manner.

In short, the coronary edge resembles a closed elastic ring, which yields
to pressure, even the most gentle, of the body-weight, in such a way that a
bulging out of any one part is manifested by an inward movement of another
part.

In Fig. 37, _b_, the dotted line represents the changes of form in
comparatively well-formed and sound hoofs at the moment of strongest
over-extension[A] of the fetlock-joint.

[Footnote A: The term 'over-extension,' as employed by Lungwitz, is
intended to indicate that position assumed by the fetlock-joint when the
opposite foot is raised from the ground.]

2. BEHAVIOUR OF THE SOLAR EDGE.--Under the action of the body-weight this
is somewhat different from that of the coronary edge. Anteriorly, and at
the sides, as far as the wall forms an acute angle with the ground,