THE FOREARM 



1423 



Soft parts. — Along the lateral border, of the forearm descend the brachio- 

 radialis and radial extensors of the carpus, fleshy above, tendinous below. About 

 3.7 cm. (1^ in.) above the styloid process of the radius, a fleshy sweUing directed 

 obliquely downward and forward from behind, across this lateral border of the 

 forearm, denotes the extensors of the thumb crossing those of the carpus. 



Along the medial border is the fleshy mass of the pronator teres and flexors, the 

 ulna being covered by the flexor carpi ulnaris and flexor profundus. The tendon 

 of the pronator is inserted into the radius a little below its centre — a point of im- 

 portance in the treatment of fractures and in amputation. The flexor carpi ul- 

 naris tendon can be felt just above the wrist making for the pisiform bone; and 

 just lateral to it lies the ulnar artery, about to pass over the transverse carpal (ante- 

 rior annular) ligament. 



The course of the artery is denoted by the lower two-thirds of a line drawn from the 

 front of the medial epicondyle to the lateral edge of the pisiform bone. From the bifurcation 

 of the brachial, a line drawn to meet the former at the junction of its middle and upper third 

 marks the upper part of the artery, here thickly covered by muscles. In ligature of the artery 

 in the middle of the forearm, the white line and sulcus between the flexor carpi ulnaris and sub- 

 limis must be identified. A small muscular branch ^vdll often lead down to the artery. The 

 line of the ulnar nerve is one drawn from the interval between the medial epicondyle and the 



Fig. 1141. — Section through the Middle of the Right Forearm. (Heath.) 



Brachio-radialis 



Supinator 

 Extensor carpi radialis longus 

 and brevis 



Abductor pollicis longus 



Extensor digitorum communis 



Extensor carpi ulnaris ^ 

 Posterior interosseous vessels and deep radial nerve 



*^§- Flexor digitorum sublimis 

 Flexor carpi ulnaris 



xjlnar vessels and nerve 



Flexor digitorum profundus 

 Median nerve 



Extensor pollicis longus 



olecranon to the medial side of the ulnar artery just above the wrist. The nerve joins the artery 

 at the junction of the upper and middle thirds of the forearm. The median nerve runs in a 

 line drawn from the medial side of the brachial artery, in the elbow triangle, to a point beneath, 

 or just to the medial side of, the palmaris longus at the mid-point of the front of the wrist. The 

 radial artery will be marked by a line drawn from the centre of the bend of the elbow (where the 

 brachial artery divides opposite to the neck of the radius) to a point just medial to the radial 

 styloid process descending along the medial edge of the brachio-radialis. The muscular interval 

 is that between the brachio-radialis and pronator teres above, and the flexor carpi radialis below. 

 The superficial radial nerve will be marked by the same line (it lies just lateral to the artery) for 

 its upper two-thirds; it then leaves the artery about 7.5 cm. (3 in.) above the wrist-joint, and 

 passes to the back of the forearm under the tendon of the brachio-radialis. The volar inter- 

 osseous artery runs down on the interosseous membrane and passes to the back of the fore- 

 arm by perforating it below, having passed behind the pronator quadratus. The dorsal 

 interosseous lies between the superficial and deep extensors. These small arteries reinforce 

 the palmar through the carpal arches, and thus bring down blood after ligature of the trunks 

 above. 



The front of the forearm is supplied by the musculo-cutaneous on the lateral, 

 and the medial antibrachial (internal) cutaneous on the medial, side; just above 

 the wrist the palmar cutaneous branches of the median and ulnar perforate the 

 deep fascia (fig. 1140). The back of the forearm is supplied by the radial (mus- 



