MUSCLES OF THE THORACIC LIMBS. 165 
that of the pectoantibrachialis (Fig. 65, 1) and is continuous 
with the general antibrachial fascia, into the caudal border of 
the cutaneous (dorsal) surface of the olecranon process of the 
ulna. 
Relations. —Outer (medial) surface with the integument, the 
latissimus dorsi (Fig. 65, 7), and the cutaneus maximus. Inner 
(lateral) surface with the biceps (Fig. 65, ¢), caput longum 
(Fig. 65, s), and caput mediale (Fig. 77, 7, 2) of the triceps. 
Action.—Extends the antibrachium and tends to supinate 
the hand by rotating the ulna. 
M. biceps brachii (Fig. 77, ¢; Fig. 65, ¢).—A thick, fusi- 
form muscle lying on the front (ventral) surface of the humerus. 
Origin (Fig. 76, c) by a strong, round tendon from the 
bicipital tubercle of the glenoid angle of the scapula, at its 
coracoid margin. (In man there is a second head—coracoid 
head—from’ the coracoid process.) The tendon passes through 
the capsule of the joint and then along the bicipital groove, 
which is converted into a canal by a strong ligament. 
‘Insertion by a rounded tendon (Fig. 87, 4) on the bicipital 
tuberosity of the radius (Fig. 86, 2). 
Relations. —The tendon of origin passes through the capsule 
of the joint, which is covered by a part of the pectoralis minor. 
The muscle is then spanned for the middle part of its course 
by. the bicipital arch (Fig. 65, ¢’), a description of which is 
given below. Farther distad it is covered by the clavobrachial 
(Fig. 65, &) and epitrochlearis (Fig. 65, 7). At its distal end 
(Fig. 79, 2’) the muscle passes between the pronator teres on 
the radial side and the conjoined tendon of the brachialis and 
clavobrachial (Fig. 79, 2’) on the other. The biceps lies 
throughout most of its length on the ventral surface of the 
humerus, and touches along the medial border of its inner sur- 
face the coracobrachialis (Fig. 77, 7), the teres major (Fig. 
77, ¢), the intermediate portion of the caput mediale of the 
triceps (Fig. 77, #), and the short portion (Fig. 77, /) of the 
same. Its lateral border touches the pectoralis minor (Fig. 
6s, 0) and the brachialis (Fig. 79, 7). 
Action.—Flexes the forearm, and tends to supinate the 
hand. 
