THE BRACHIAL PLEXUS. 



1307 



and passes downward and outward beneath the axillary artery and the circumflex 

 and musculo-spiral nerves. It sends fibres to the inferior portion of the subscap- 

 ularis muscle and terminates in the substance of the teres major. 



Variations. As regards origin the upper may arise from either the fifth or the sixth cervi- 

 cal nerve, the middle from the seventh alone or from the seventh and eighth or rarely by an 

 additional filament from the fifth, and the lower from the fifth, sixth and seventh or from the 

 fifth or sixth alone. As regards distribution, the nerves to the lower part of the subscapularis 

 and to the teres major may proceed separately from the brachial plexus or the latter nerve 

 may be a branch of the circumflex. 



15. THE CIRCUMFLEX NERVE. 



The circumflex or axillary nerve (n. axillaris) (Fig. 1092) is one of the terminal 

 branches of the posterior cord and contains fibres which are derivatives of the fifth 



FIG. 1099. 



Median nerve 

 Flexor longus pollicis 



Palmar cutaneous br. of median nerve 



Opponens pollicis 



Adductor obliquus pollicis 



Flex. brev. poll., 



inner head 

 Flex. brev. poll., 



outer head " 



Adductor pollicis 



Adductor transversus 

 poll. 



An articular branch 



Flex. prof, digitorum, 

 in part 



Ulnar nerve 

 Flex, carpi ulnaris 



Pisiform bone 

 Deep br. of ulnar nerve 

 Articular br. of ulnar 

 Unciform bone t nerve 

 Articular brs. of ulnar 

 nerve [everted 



Abductor minimi digiti, 

 Opponens minimi digiti 

 Second palmar inter- 

 osseous 



Third dorsal interosseous 

 Third palmar inter- 

 Fourth dorsal [osseous 

 interosseous 

 Flex, brevis minimi 

 digiti 



Dissection of right palm, showing distribution of deep branch of ulnar ; flexor tendons of third and fourth 

 fingers, with corresponding lumbricales, divided and turned down. 



and sixth cervical nerves. It arises near the lower margin of the subscapularis and 

 posterior to the axillary artery. Accompanied by the posterior circumflex artery it 

 takes a backward course through the quadrilateral space, bounded above by the 

 subscapularis and the teres minor, below by the teres major, internally by the 



