1 40 THE SUPERIOR EXTREMITY 



p. 147). This attachment is placed on the summit of the 

 chief curve of the radius, an arrangement which enables the 

 muscle to exercise its pronating action at a great advantage. 

 Close to its insertion the pronator teres is crossed by the 

 radial artery and it is covered by the brachio-radialis muscle. 

 It is supplied by the median nerve. It is a pronator of the 

 forearm and hand and a flexor of the elbow. 



M. Flexor Carpi Radialis. The flexor carpi radialis arises 

 from the common tendon, from the fascia of the forearm 

 and the fibrous septa which intervene between it and the 

 adjacent muscles. Its fleshy belly gives place, a short distance 

 distal to the middle of the forearm, to a long flattened tendon, 

 which, at the wrist, traverses the groove on the front of the 

 os multangulum majus, in a special compartment of the trans- 

 verse carpal ligament (Fig. 60, p. 137). It is inserted into 

 the volar aspect of the base of the metacarpal bone of the 

 index, and slightly also into the base of the metacarpal bone 

 of the middle finger. Its relations to the transverse carpal 

 ligament, and also its attachment to the metacarpus, will be 

 exposed and studied at a later stage of the dissection. It 

 is a flexor of the wrist and elbow joints and assists in 

 producing abduction of the hand. It is supplied by the 

 median nerve. 



M. Palmaris Longus. The palmaris longus is a long slender 

 muscle, which is not always present. It springs from the 

 common origin, the fascial investment of the forearm and the 

 fibrous septum on each side of it. Its tendon pierces the 

 deep fascia immediately proximal to the wrist, and then passes 

 distally, superficial to the transverse carpal ligament, to join the 

 strong intermediate portion of the palmar aponeurosis. Very 

 frequently it gives a slip to the abductor pollicis brevis. It is 

 supplied by the median nerve, and is a flexor of the radio- 

 carpal and elbow joints. 



M. Flexor Carpi Ulnaris. The ulnar flexor of the carpus 

 muscle arises by two heads. One of them is incorporated 

 with the common origin from the medial epicondyle; the 

 other springs from the medial border of the olecranon of the 

 ulna, and also by an aponeurotic attachment from the dorsal 

 border of the same bone in its proximal two-thirds. Fibres 

 are derived also from the investing fascia and the inter- 

 muscular septum on its lateral side. The two heads of origin 

 of the flexor carpi ulnaris bridge across the interval between 



