986 



THE NERVOUS SYSTEM 



branch, the superficial radial, which supplies the dorsal aspect of the radial half 

 of the hand. 



The deep radial [ramus profundus] (posterior interosseous) nerve runs down- 

 ward in the interval between the brachialis and extensor carpi radialis longus. 

 It passes in front of the lateral part of the elbow-joint, and after giving off branches 

 to supply the extensor carpi radialis brevis and supinator, it is crossed in front 

 by the radial recurrent artery (fig. 759). It then runs downward and dorsal ward 

 through the substance of the supinator, and enters the interval between the 

 superficial and deep layers of muscles at the back of the forearm, where it comes 

 into relation with the posterior interosseous artery, and accompanies it across 



Fig. 757. — A Dissection of the Cutaneous Nerves on the Dorsal Aspect op the Hand 



AND Fingers. (H. St. J. B.) 

 The branches of the median nerve are shown in black. 



Dorsal branch of 

 ulnar nerve 



Branch of radial (musculo-spiral) 



Superficial radial (radial) nerve 



the abductor pollicis longus. At the lower border of the latter muscle it gives off 

 a branch to the extensor pollicis longus, and another which crosses this muscle to 

 the extensor indicis proprius. 



Continuing distalward as the dorsal antibrnchial inleroRffeous nerve the deep radial leaves the 

 posterior interosseous artery, dips beneath the extensor pollicis longus, and joins the volar inter- 

 osseous artery. It accoinpani(!s this artery upon the interosseous membrane and upon the back 

 of tlio radius, passes tlirough the groove for the extensor digitorum comnumis and extensor 

 indicis proprius to the dorsum of the wrist, and terminates in a gangliform eidargement which 

 gives branches to the carpal articulations. The muscles supplied by the deep radial nerve 

 are the extensor carpi radialis brevis, brachio-radialis (supinator longus), extensor digitorum 

 communis, exten.sor digiti {juinti proprius, exicnsor car])i uinaris, extensor indicis proprius, 

 and the extensor muscles of the thundi. The sujiinator (brevis) receives two twigs, one of which 

 is given off before the nerve pierces the muscle and the other while it is passing through it. 



