2. Muscles of the Brachium or Upper Arm.
M. clavobrachialis and the pectoralis group ([Fig. 65], [page 109]) lie partly in this region; they have been [described].
M. coracobrachialis ([Fig. 77], f; [Fig. 79], c).—A very short muscle covering the inner (medial) surface of the capsule of the shoulder-joint. It extends from the coracoid process to the proximal end of the humerus.
Origin ([Fig. 78], h).—By a round tendon from the tip of the coracoid process.
Insertion ([Fig. 82], e) usually by fleshy fibres on an area five to eight millimeters long and about half as wide, which lies on the medial side of the humerus parallel with the ridge which runs from the dorsal end of the lesser tuberosity to the shaft and close to it. The proximal end of the area is about one centimeter from the proximal end of the head of the humerus.
Relations.—Medial surface with the biceps ([Fig. 77], g), pectoralis minor ([Fig. 65], o), and teres major ([Fig. 77], c). Lateral surface with the capsule of the shoulder-joint. Dorsal border with the subscapularis ([Fig. 77], a) and the long portion of the caput mediale of the triceps ([Fig. 77], j).
Action.—Adducts the humerus.
The part of the coracobrachialis just [described] is known as the short head. A long head is sometimes found. It is a conical bundle of fibres of varying size, which arises from the tendon of origin of the short head. It passes distad into a long and extremely slender tendon, the insertion of which varies greatly in different individuals. It is commonly on the humerus in the region of the supracondyloid foramen.
M. epitrochlearis or extensor antibrachii longus ([Fig. 65], r).—A thin, flat muscle on the inner or medial side of the brachium, from the lateral surface of the latissimus dorsi ([Fig. 65], q) to the olecranon process of the ulna.
Origin from the lateral or outer surface of the ventral border of the latissimus dorsi ([Fig. 65], q) near the insertion of the cutaneus maximus. Fibres are often attached to the teres major and the pectoralis minor.