This consists of two lateral pieces, the LATERAL CARTILAGES or
_Fibro-cartilages_ of the pedal bone, united behind and below by the
_Plantar Cushion_.

1. THE LATERAL CARTILAGES.--Each is a flattened plate of cartilage,
possessing two faces and four borders separated by four angles.

The external face is convex, covered by a plexus of veins, and slightly
overhangs the pedal bone. The internal face is concave, and covers in
front the pedal articulation and the synovial sac, already mentioned as
protruding between the antero- and postero-lateral ligaments of that joint.
We have already remarked that this is a point of interest to be remembered
in connection with the operation for quittor. Below and behind, the
internal face of the cartilage is united to the plantar cushion.

[Illustration: FIG. 16.--EXTERNAL FACE OF THE OUTER LATERAL CARTILAGE. 1,
External face of cartilage--(_a_) its upper border, (_b_) its posterior
border, (_c_) its anterior border, (_d_) its inferior border; 2, the os
pedis; 3, wing of os pedis.]

The upper border, sometimes convex, sometimes straight, is thin and
bevelled, and may easily be felt in the living animal. It is this border
that the digital vessels cross to gain the foot, and the border is often
broken by a deep notch to accommodate them. The inferior border is attached
in front to the basilar and retrossal processes, behind which it blends
with the plantar cushion. The posterior border is oblique from before to
behind, and above to below, and joins the preceding two. The anterior
border is oblique in the same direction, and is intimately attached to the
antero-lateral ligament of the pedal articulation. The cartilages of the