kward and outward movements of the latter will tend to pull
upon and tighten the former, especially _in front_. This will account for
the contraction noted by Lungwitz in the _anterior half_ of the coronary
edge of the hoof.

Remove the body-weight, and naturally the elastic nature of the lateral
cartilages and the coronary and plantar cushions, with, in a less degree,
that of the hoof, cause things to assume their normal position.

Repeat the weighting of the hoof, in this second case _without
frog-pressure_, and we shall see at once that we have done away with one of
the greatest factors in determining the outward and backward movements of
the plantar cushion--namely, the pressure from below on its wedge-shaped
mass. The movement of the plantar cushion will now be _downwards_ as well
as backwards; and, seeing that it is attached to the inner aspect of each
lateral cartilage, we shall expect these latter, by the downward movement
of the plantar cushion, to be drawn _inwards_. This Lungwitz has shown to
occur.

The chief function of the lateral cartilages, therefore, is to _receive
the concussion engendered by locomotion_, which concussion is directed
backwards and outwards by the pad-like plantar cushion.

In addition to this, the lateral cartilages, together with the plantar and
coronary cushions, _play the part of a valve to the whole of the veins of
the foot_.

It is in this way: We have only to refer to the chapter on anatomy to see
that the whole of the foot is covered with a tissue of extreme vascularity.
Thus we find papillae--the over the coronary cushion; enlarged and modified
papillae sensitive laminae--covering the anterior face of the os pedis; and
numberless papillae again covering the sole. There can be no doubt that the
quantity of fluid brought by the bloodvessels of these papillae to the foot
acts largely as a means of hydraulic protection to the soft structures.[A]
In like manner as that delicate organ, the brain, is best protected by
being floated upon the cerebro-spinal fluid and bloodvessels (which fluids
transmit waves of concussion or pressure _through_ the organ without injury
to the delicate cells forming it), so, in like manner, does the extreme
vascularity of the foot protect the cells of its softer structures from the
effects of pressure and concussion.

[Footnote A: The _Veterinary Record_, vol. iii., p. 518.]

That this law of hydraulics may operate in the horse's foot to the best
a