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, /) by a short strong tendon from the 

 extremity of the medial epicondyle of the humerus. 



Insertion (Fig. 86, /) 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, /'), with the 

 extensor carpi radialis brevis (Fig. 77, /), and the supinator 

 (Fig. 85, b). Ulnar border with the flexor carpi radialis (Fig. 

 77, r] and part of the flexor profundus digitorum (Fig. 77, w). 



Action. Pronates the hand by rotating the radius. 



M. flexor carpi radialis (Fig. 77, r). A slender fusiform 

 muscle. 



Origin (Fig. 82, ;) 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 (q]. 

 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 (//) 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, /) by a 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) 



