Because of the shape of the cushion its change of form cannot be forwards (simultaneous pressure from above and below on to this wedge with its apex forwards must tend to give it a backward change of form). Because of the pastern being horizontal, and aiding in the downward pressure, its change of form cannot be upwards. And because of the ground it cannot be downwards. It follows, therefore, that the movement must be backwards and outwards, being especially directed outwards because of its shape and the median lacuna in its posterior half--this latter, the lacuna, accommodating as it does the frog-stay, preventing the tendency to backward movement becoming excessive, and directing the change of form to the sides. Where the greatest pressure is transmitted, then, is to the inner aspects of the flexible lateral cartilages. The coronary cushion being continuous with the plantar, the backward 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_.