MUSCLES OF THE THORACIC LIMBS. 179 
B. MUSCLES ON THE RADIAL AND VENTRAL SIDE OF 
THE FOREARM (flexors and pronators). 
M. pronator teres (Fig. 77, ¢). 
Origin (Fig. 82, 2) by a short strong tendon from the 
extremity of the medial epicondyle of the humerus. 
Insertion (Fig. 86, 2) by fleshy fibres and short tendinous 
fibres along the medial border of the radius, at its middle. 
The radial edge of the muscle is continuous with the strong 
deep layer of the antibrachial fascia. 
Relations.—-Outer surface with the superficial fascia. Radial 
border with the tendon of the biceps (Fig. 79, 7’), with the 
extensor carpi radialis brevis (Fig. 77, p), and the supinator 
(Fig. 85, 2). Ulnar border with the flexor carpi radialis (Fig. 
77, r) and part of the flexor profundus digitorum (Fig. 77, u). 
Action.—Pronates the hand by rotating the radius. 
M. flexor carpi radialis (Fig. 77, ~).—A slender fusiform 
muscle. 
Origin (Fig. 82, m) from the tip of the medial epicondyle 
of the humerus. 
Insertion.—The slender tendon passes through a deep 
groove between the os magnum and the first metacarpal. The 
groove is converted into a canal by the overlying tendons and 
muscles. The tendon is finally inserted into the bases of the 
second and third metacarpals. 
Relations.—Outer surface with the pronator teres (Fig. 
77, q), the superficial fascia, and the third head of the flexor 
profundus (#). Radial border with the pronator teres (g). 
Ulnar border with the third and fourth heads of the flexor pro- 
fundus. Inner surface with the ulna proximad and the fifth 
head of the flexor profundus (z’) distad. 
Action indicated by the name. 
M. palmaris longus (Fig. 77, s).—A flat fusiform muscle 
beneath the fascia on the medial border of the forearm. 
Origin (Fig. 82, p) bya short flat tendon from the distal part 
of the medial surface of the medial epicondyle of the humerus. 
About one centimeter from the wrist the muscle ends in a 
flat tendon which passes through the transverse ligament and 
divides on the hand into four or five (or sometimes only three) 
