for the function which
they perform. The several bones which go to make up the supportive
portion of the leg, are so joined at their points of articulation, that
a minimum degree of strain is put upon each attachment.

The upper third of the scapula, with its cartilage of prolongation, is
sufficiently broad and flattened that it fits snugly against the thorax
without necessity for a complicated method of attachment--the clavicle
being absent, attachment is muscular.

Smith[5] has very aptly stated that:

"It seems quite legitimate to regard the muscular union between the
thorax and forelimb as a joint. There are no bones resting on each
other, no synovia; but where the scapula has its largest range of
movement there is a remarkable amount of areolar tissue, which renders
movement easy. The whole central area beneath the scapula and humerus
not occupied by muscular attachment, is filled with this easy-moving,
apparently gaseously distended, crepitant, areolar tissue over which the
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. fuer Kuenstler.) (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; wh