(hinge) joints. Two common lateral ligaments bind the bones together.
While bearing weight, there is assumed a position of slight dorsal
flexion, undue flexion being checked by the inhibitory apparatus of the
joint--check ligaments, and their tendons and the suspensory ligament.
The inhibitory apparatus of the fetlock joint is materially reinforced
by the proximal sesamoid bones. Situated as they are, between the
bifurcating portions of the suspensory ligament and the posterior part
of the distal end of the metacarpus--with which they articulate--the
sesamoid bones serve to change the course of the branches of the
suspensory ligament in a manner that they give firm support to this
joint. Volar flexion is limited by the extensors of the phalanges.

[Illustration: Fig. 4--Sagital Section of Digit and Distal Part of
Metacarpus.

A, Metacarpal bone; B, first phalanx; C, second phalanx, D, third
phalanx; E, distal sesamoid bone; 1, volar pouch of capsule of fetlock
joint; 2, inter-sesamoidean ligament; 3, 4, proximal end of digital
synovial sheath; 5, ring formed by superficial flexor tendon; 6, fibrous
tissue underlying ergot; 7, ergot; 8, 9, 9', branches of digital
vessels; 10, distal ligament of distal sesamoid bone; 11, suspensory
ligament of distal sesamoid bone; 12, 12', proximal and distal ends of
bursa podotrochlearis. (From Sisson's "Anatomy of the Domestic
Animals").]

The first phalanx (os suffraginis) normally sets at an angle of about
50 to 55 degrees from a horizontal plane while weight is being
supported. Its distal end articulates with the second or median phalanx
(os corona) and forms the proximal interphalangeal (pastern or
suffraginocoronary) joint. This also, is a ginglymus joint, having but