352 A MANUAL OF ANATOMY 



ulna, and, after a short course, it joins the deep surface of the super- 

 ficial head at an acute angle. 



Insertion. — By means of a flat tendon, about i| inches broad, 

 into the rough impression on the outer surface of the radius at its 

 centre, where the curve of the bone is most prominent. 



Nerve-supply. — The median nerve, which arises from the outer and 

 inner cords of the brachial plexus, its fibres being derived from the 

 last four cervical and first thoracic nerves. The branches are given 

 off just before the median nerve passes between the two heads of 

 origin of the muscle. 



The muscle is directed downwards and outwards. 



Action. — (i) To pronate the forearm, and (2) to assist inflexion 

 of the elbow- joint. 



The median nerve passes between the two heads of the muscle, and 

 the ulnar vessels beneath its deep head. 



The muscle may have a third head, arising from the internal inter- 

 muscular septum of the arm, or from a supracondylar process, and, 

 when this is so, it bridges over the brachial artery and median 

 nerve. 



2. Flexor Carpi Radialis — Origin. — (i) The front of the internal 

 epicondyle by means of the common tendon ; (2) the deep fascia 

 covering the muscle ; and (3) the intermuscular septa separating it 

 from the pronator radii teres externally, palmaris longus internally, 

 and flexor sublimis digitorum deeply. 



Insertion. — The front of the base of the second metacarpal bone, 

 and by a small slip into the front of the base of the third. 



The muscle presents a fusiform, fleshy belly in the upper half of the 

 forearm, which is replaced in the lower half by a strong, flat tendon. 



Nerve-supply. — ^The median nerve. 



The direction of the muscle is downwards and outwards. 



Action. — (i) To flex the wrist-joint, and (2) to assist in flexion of 

 the elbow- joint. 



The tendon of the muscle passes through a special compart- 

 ment of the anterior annular ligament, where it traverses the 

 groove on the palmar surface of the trapezium, and the radial 

 vessels lie upon the outer side of the tendon in the lower half of the 

 forearm. 



3. Palmaris Longus — Origin. — (i) The front of the internal epi- 

 condyle by means of the common tendon ; (2) the deep fascia cover- 

 ing the muscle ; and (3) the intermuscular septa separating it from 

 the flexor carpi radialis externally, flexor carpi ulnaris internally, 

 and flexor sublimis digitorum deeply. 



Insertion. — (i) The upper part of the central division of the palmar 

 fascia, and (2) the front of the anterior annular ligament at its 

 lower part. 



Nerve-supply. — ^The median nerve. 



Action. — (i) To render tense the central division of the palmar 

 fascia ; (2) to assist in flexing the wrist-joint ; and (3) to assist 

 feebly in flexing the elbow- joint. 



