INNER ASPECT OF LIMB 27 



The Circumfiex Nerve (14). — This nerve derives its fibres from the 

 sixth, seventh, and eighth cervical nerves. In the plate it is seen to pass 

 downwards and backwards under the posterior root of the median nerve. 

 This is due to the twisting which the plexus has undergone. It passes 

 in front of the long branch of the subscapular artery to twist round the 

 back of the shoulder joint, to the muscles and skin on the outer aspect 

 of which it is distributed {i.e., teres minor, deltoid, and mastoido- 

 humeralis). 



The Musculo-spiral Nerve (16). — This is the thickest nerve given off 

 by the plexus. Its fibres come from the seventh and eighth cervical and 

 the first and second dorsal roots. The nerve runs downwards and back- 

 wards on the subscapularis muscle, and crosses the subscapular artery and 

 the artery to the latissimus dorsi muscle. It next lies on the teres major 

 muscle behind the axillary and brachial vessels (see ulnar nerve). About 

 midway down the shaft of the humerus it meets the deep humeral artery, 

 and disappears with this vessel in front of the large head of the triceps 

 extensor cubiti muscle. It is not again visible in the plate. 



The Nerve to the Teres Major (12). — This nerve has a common origin 

 from the plexus with the circumflex nerve. It takes a course down- 

 wards and backwards, crossing the subscapularis muscle and the 

 subscapular artery which runs along the glenoid border of the scapula, 

 to reach the teres major muscle which it supplies. Only a small portion 

 of this nerve is represented. 



The Nerve to the Latissimus Dorsi (6). — The eighth cervical and first 

 dorsal roots supply the fibres to this nerve. It runs backwards across 

 the subscapularis and teres major muscles to the muscle which it supplies. 



The Subcutaneous Thoracic Nerve (8). — This is a very long nerve which 

 arises from the eighth cervical and dorsal roots of the plexus in close 

 relationship to the ulnar nerve. It passes backwards across the teres 

 major and the deep face of the large head of the triceps extensor cubiri 

 muscle, and its subsequent course is not represented, and does not concern 

 us here. 



