MUSCULO-SPIEAL NERVE 191 



2. Muscular to brachialis anticus, supinator longus, and 

 extensor carpi radialis longior. 



3. Radial nerve passes down the upper two-thirds of the 

 forearm external to the radial artery and covered by supinator 

 longus. It pierces the deep fascia on the outer side of the lower 

 third of the forearm, and passes to the back of the wrist. It 

 supplies the skin on the back of the wrist, the radial side of the 

 back of the hand and the back of the thumb, first and second 

 fingers, and radial side of the third finger as far as the second 

 phalanges, the rest being supplied by the median nerve. 



4. Posterior Interosseous nerve is entirely muscular and articu- 

 lar in its distribution. It reaches the back of the forearm by 

 passing from under supinator longus round the outer side of the 

 radius, and pierces supinator brevis. On the back of the forearm 

 it passes beneath the extensor muscles with the posterior inter- 

 osseous artery, then gets on the interosseous membrane by 

 passing beneath extensor longus pollicis, and terminates in a 

 gangliform enlargement on the back of the wrist. 



Branches. Articular to the carpal joints. 



Muscular to extensor carpi radialis brevis, supinator brevis, 

 and all the extensor muscles on the back of the forearm. 



Subseapular Nerves. There are three subscapular nerves 

 arising from the posterior cord of the brachial plexus. They 

 all pass down behind the axillary artery, and are all purely 

 muscular : 



First or short subscapular nerve to subscapularis. 



Second or lower subscapular nerve to teres major. 



Third or long subscapular nerve to latissimus dorsi. 



