712 



THE NEKVOUS SYSTEM. 



KAMUS SUPERFICIALIS NERVI EADIALIS. 



The superficial ramus (O.T. radial nerve) is entirely cutaneous in its dis- 

 tribution. Arising in the hollow of the elbow beneath the brachio-radialis, it courses 



distally under cover of that 

 muscle through the proximal 

 two -thirds of the forearm, 

 and accompanies the radial 

 artery in the middle third of 

 the forearm. It then passes 

 backwards, under cover of the 

 tendon of the brachio-radialis, 

 and pierces the deep fascia on 

 the lateral aspect of the fore- 

 arm in the distal third. It is 

 distributed to the skin of the 

 dorsum of the wrist, the lateral 

 side and the dorsum of the 

 hand, and the dorsum of the 

 thumb and lateral two and a 

 half fingers (Fig. 618, p. 707). 

 Its branches communicate, on 

 the ball of the thumb, with 

 the musculo-cutaneous nerve, 

 and, on the dorsum of the 

 hand, with the dorsal branch 

 of the ulnar nerve (ramus 

 anastomoticus ulnaris). The 

 digital nerves are small, and 

 are five in number. Two 

 pass to the back of the thumb 

 and reach the level of the 

 inter-phalangeal articulation. 

 One supplies the lateral side 

 of the index finger as far as 

 the second phalanx. The re- 

 maining two branches divide 

 at the clefts between the 

 second and third, and third 

 and fourth fingers respect- 

 ively, and innervate the ad- 

 jacent sides of those fingers 

 as far as the second phalanx. 

 The rest of the skin of those 

 digits to the tips is supplie 

 by digital branches of tl 

 median nerve. The nerve mai 

 only supply the thumb am 

 one and a half fingers, beinj 

 replaced by branches from tl 

 ulnar nerve. 



Radial nerv 



Superficial ramus r 

 Deep ramus- 



Deep ramus ^~" 



Muscular branches to superficial muscles^-" 

 Dorsal interosseous artery''' 



Dorsal interosseous nerve 



Muscular branch to abductor pollicis longus. 

 Muscular branch to extensor pollicis longus,- 

 Muscular branch to extensor indicis propri 

 Muscular branch to extensor pollicis brevis *~ 



Terminal branch to carpal joints *~- 



FIG. 621. DISTRIBUTION OF THE DEEP BRANCH OF THE 

 RADIAL NERVE. 



KAMUS PROFUNDUS NERVI EADIALIS. 



The deep ramus (O.T. posterior interosseous nerve) is entirely muscular am 

 articular in its distribution. It arises, like the superficial ramus, under cover of th< 

 brachio-radialis muscle. Directed obliquely distally and backwards, it reactu 

 the back of the forearm, after passing round the lateral aspect of the radius, 

 piercing the fibres of the supinator muscle (Fig. 621). On the dorsal surface of th 



