ANTERIOR THORACIC. SUBSCAPULAR NERVES. 



645 



Some differences will be found in the statements of anatomists who have 

 investigated the subject for instance, Scarpa (" Annotations Anatom.")and Kronen- 

 berg (" Plex. nervor. Structura et Virtutes ") with respect to the nerves to which 

 the branches are assigned. This difference is mainly owing to the variation which 

 actually exists in different cases. 



ANTERIOR THORACIC NERVES. 



The anterior thoracic nerves, two in number, supply the pectoral 

 muscles. 



The external, or more superficial branch, arising from the outer cord, 

 crosses inwards over the axillary artery, and terminates in the great pectoral 

 muscle. 



The internal, or deeper branch, springing from the inner cord, comes 

 forwards between the axillary artery and vein to the small pectoral muscle, 

 and is joined by a branch from the exterual. This nerve presents a plexi- 

 form division beneath the small pectoral muscle, and supplies branches to 

 it and the larger pectoral muscle. The two nerves are connected by a tila- 

 ment which forms a loop over the artery at the inner side. 



SUBSCAPULAR NERVES. 



These nerves, three in number, take origin from 

 the posterior cord of the plexus. 



The upper nerve, the smallest of the sub- 

 scapular nerves, penetrates the upper part of the 

 subscapular muscle. The lower nerve gives a 

 branch to the subscapularis at its axillary border, 

 and ends in the teres major muscle. There is 

 sometimes a distinct nerve for the last-named 

 muscle. 



The long subscapular nerve, the largest of the 

 three, runs along the lower border of the sub- 

 scapular muscle to the lutissinius dorsi, to which 

 it is distributed. 



Fig. 427. DISTRIBUTION OF THE POSTKRIOR CUTANEOUS 

 NERVES OP THE SHOULDER AND ARM (from Hirschfeld 

 and Leveille). I 



1, supra-acromial branches of the cervical nerves de- 

 scending on the deltoid muscle ; 2, ascending or reflected, 

 and 2', descending cutaneous branches of the circumflex 

 nerve ; 3, inferior external cutaneous of the musculo-spiral 

 nerve ; 4, external and posterior cutaneous branches of the 

 niusculo-cutaneous nerve to the forearm ; 5, internal 

 cutaneous of the musculo-spiral ; 6, intercosto-humeral 

 branches ; 7, twigs of the nerve of Wrisberg ; 8, upper 

 posterior branch of the internal cutaneous nerve ; 9, lower 

 branch of the same. 



CIRCUMFLEX NERVE. 



The circumflex or axillary nerve gives both 

 muscular and cutaneous nerves to the shoulder. 

 Springing from the posterior cord, this nerve is at 

 first placed behind the axillary artery, but at the 

 lower border of the subscapular muscle it is inclined backwards with the 

 posterior circumflex artery, in the space between the scapula and tere& 



