Part 34

Origin.—By a delicate tendon from a small circular point on the postero-mesial part of the shaft of the coracoid immediately above the attachment of the subclavius and the fossa at that point.

Insertion.—To the top of the ulnar tuberosity of the humerus. This subcircular space is common to the teres minor and to this muscle.

Shape.—Long, fusiform.

Relations.—With the shaft of the coracoid between the teres minor and subscapularis.

Action.—To depress the wing.

=Teres Minor= (Fig. 13, No. 14). Location.—The coraco-scapular region.

Origin.—From under the side of the anterior tip of the scapula.

Insertion.—Passing outward behind the coracoid head and beneath the neck of the scapula, it is attached by a small tendon to the top of the ulnar tuberosity of the humerus in common with the coraco-brachialis, with which tendon it fuses.

Shape.—Small, chunky.

Relations.—Anteriorly, with the tip of the scapula and behind the coracoid head. Posteriorly, with the coraco-brachialis.

Action.—Aids in the downward stroke of the wing.

=Levator Scapulæ.= Location.—Scapular region.

Origin.—By two strong digitations, one from each of the lateral processes of the first cervical vertebra.

Insertion.—To the middle third of the inferior part of the blade of the scapula.

Shape.—Small and flat.

Relations.—Inferior to the scapula.

Action.—Pulls the scapula forward, and with it the entire shoulder girdle, which articulates like a hinge-joint at the costo-sternal juncture.

=Thoraco-scapularis.= Location.—Lateral side of the chest.

Origin.—From the outer part of the lower half of the first free rib, the outer side of the next succeeding rib and its epineural appendage, and from a similar surface on the next rib.

Insertion.—By a broad, flat tendon which passes between the two divisions of the subscapularis and inserts at a point at the juncture of the anterior and middle third of the outer margin of the scapula.

Shape.—Broad, flat.

Relations.—Internally, with the ribs and the scapula.

Action.—When the scapula is fixed it is a muscle of inspiration. When the ribs are fixed, it draws the scapula downward.

=Subscapularis.= Location.—Scapulo-humeral region.

Origin.—From the anterior and outer half of the scapula.

Insertion.—By a strong and subcylindrical tendon to the top of the ulnar tuberosity of the humerus close to the combined tendons of the coraco-brachialis and teres minor.

Shape.—A large and powerful muscle.

Relations.—The flat tendon of the thoraco-scapularis divides the posterior portion of the belly into two portions.