FOREARM, WRIST, AND HAND. 



the Interossei, two inner Lumbricales, and the Flexor brevis 

 (deep part) and Adductores, obliquus and transversus, pol- 

 licis. [630] 



Internal Cutaneous. This divides in front of the elbow 

 into two branches. The anterior descends to the wrist, sup- 

 plying the inner half of the forearm in front; the internal runs 

 downward and backward, supplying the upper two-thirds, or 

 three-fourths, of the back of the forearm internally. [631] 



Musculo-spiral. Before dividing in front of the elbow into 

 the radial and posterior interosseous, this gives off two cuta- 

 neous branches which descend behind the external condyle. 

 The superior branch supplies the upper half of the back of the 

 forearm, and the inferior branch the upper two- thirds of the 

 back of the forearm, internal to the area supplied by the 

 musculo-cutaneous. [633] 



Radial. This cutaneous nerve descends under the Brachio- 

 radialis and, lower down, on the outer side of the radial ar- 

 tery, passes backward under the Brachio-radialis tendon and 

 pierces the deep fascia on the outer side of the forearm. It 

 supplies the back of the wrist and hand, and divides into five 

 digital branches; two supply the back of the thumb as far as 

 the inter-phalangeal joint, one supplies the radial side of the 

 index finger as far as the second phalanx; the others subdi- 

 vide at the finger clefts to supply the adjacent sides of the 

 second, third, and fourth fingers, as far as the second phalanges. 

 It communicates with the musculo-cutaneous on the ball of 

 the thumb, and the ulnar (dorsal branch) on the back of the 

 hand. [634] 



Posterior Interosseous. This runs downward and backward 

 through the Supinator brevis and round the outer side of the 

 radius. Then descending on the back of the forearm under the 

 superficial extensors and with the posterior interosseous ar- 

 tery, it passes under the Extensor longus pollicis and upon the 

 interosseous membrane. Then running under the extensor 

 tendons to the back of the carpus it ends in a gangliform en- 

 12 [ 177 ] 



