ereas flexion,
beyond desirable limits, is inhibited by the biceps brachii (flexor
brachii or coracoradialis) muscle.

The distal end of the humerus, however, articulating with the radius and
ulna in a fashion that no support is lent by any sort of contact with
the body, is a ginglymus (hinge) joint and lateral motion, because of
the long transverse diameter of its articular portions, is easily
prevented by the medial and lateral ligaments (internal and external
ligaments). Flexion of this, the humeroradioulnar joint (elbow), is
restrained by the triceps brachii and extension is checked by the biceps
brachii (flexor brachii).

The carpal joint (erroneously called the knee joint), is composed of the
several carpal bones which interarticulate and, when taken as a group,
serve as a means of attachment and articulation for the radius and
metacarpal bones.

The transverse diameter of this joint is long, thus giving it contacting
surfaces that are sufficiently extensive to minimize the strain upon the
mesial and lateral ligaments (internal and external lateral common
ligaments). Motion is that of flexion and extension; slight rotation is
possible when the position is that of flexion. While supporting weight
the carpus is fixed in position by a slight dorsal flexion, but undue
dorsal flexion is prevented by the flexor muscles and tendons and
volar-carpal or annular ligament, together with the superior check
ligament.

The metacarpophalangeal articulation (fetlock joint), is a hinge joint
and its articular surfaces contact one another, with respect to their
having a long bearing surface from side to side, as do all ginglymus
(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 Di