fore legs glide on the chest wall as freely as if the parts were a
large, well lubricated joint."

The scapulohumeral articulation (shoulder joint) is an enarthrodial
(ball and socket) joint but because of its being held more or less
firmly against the thoracic wall by muscular and tendinous attachment,
and because a part of this attachment affords a means of support for the
body itself, there is no need for binding ligaments and movement is
possible in all directions even though restricted as to extent.

[Illustration: Fig. 2--Muscles of Left Thoracic Limb from Elbow
Downward; Lateral (External) View.

a, Extensor carpi radialis; g, brachialis; g', anterior superficial
pectoral; c, common digital extensor; e, ulnaris lateralis. (After
Ellenberger-Baum, Anat. für Künstler.) (From Sisson's "Anatomy of the
Domestic Animals").]

[Illustration: Fig. 3--Muscles of Left Thoracic Limb from Elbow
Downward; Medial (Internal) View.

The fascia and the ulnar head of the flexor carpi ulnaris have been
removed. 1, Distal end of humerus; 2, median vessels and nerve. (From
Sisson's "Anatomy of the Domestic Animals").]

Undue extension, (by extension is meant such movement as will cause the
long axis of two articulating bones to assume a position which
approaches or forms a straight line--opposite to flexion), of the
scapulohumeral joint is impossible while weight is borne, because of the
normally flexed position of the humerus on the scapula; whereas flexion,