8 



laris and from the brachial plexus, in common with the N. medianus (PI. I, 

 30, 31). Carefvdly dissect up the overlying posterior portion or sternal 

 extremity of the anterior deep pectoral and trace the nerves to their respec- 

 tive places of distribution in the superficial pectoral muscles. The two or 

 more nerves to the posterior deep pectoral and the panniculus are readily 

 found. They arise from the brachial plexus apparently in common with 

 the Nn. medianus and ulnaris. The smaller and more anterior of the 

 two nerves (in the present specimen) soon divides into three or four 

 branches which enter the muscle near its humeral end along with the 

 artery and vein supplied to the muscle. The larger and more posterior 

 nerve also divides into several branches some of which are distributed to 

 the posterior deep pectoral and some to the panniculus ; note particularly 

 the large branch which accompanies the large V. thoracica externa which 

 runs along the dorsal margin of the posterior deep pectoral and is continued 

 posteriorly in the panniculus. 



A. suprascapularis arises from the A. axillaris near the anterior border of 

 the tendon of the subscapularis, and close to the N. musculo-cutaneous 

 where it crosses the A. axillaris. About one centimeter from its origin 

 the A. suprascapularis divides into two branches, of which one is distributed 

 to the subscapularis, anterior deep pectoral and the supraspinatus ; the 

 other branch is distributed to the anterior deep pectoral, supraspinatus, 

 the shoulder joint, and the proximal tendon of the biceps. The artery is 

 accompanied by the V. suprascapiilaris. 



N. suprascapularis (PL I, 28; PI. II, 21) originates from the 7th and 8th 

 cervical nerves but principally from the 7th; occasionally some fibres 

 originate from the 6th cervical nerve also. This large nerve passes between 

 the adjacent borders of the supraspinatus and subscapularis. Carefully 

 dissect the supraspinatus from the adjoining subscapularis, on one side 

 of it, and the infraspinatus, on the other, and transect the muscle opposite 

 the N. suprascapularis. Reflect the muscle sufficiently to expose the 

 two or three large branches of the nerve to the supraspinatus, which branches 

 are given off just as the nerve crosses the anterior border of the scapula. 

 Trace the nerve across the supraspinus fossa and note its width, i to 2 cm. 

 opposite the spine of the scaptila. Just as the nerve enters the M. infra- 

 spinatus it divides into 5 or 6 branches, all of which are distributed to this 

 muscle. 



Nn. subscapulares (PI. I, 47). There are usually two or more of these 

 nerves. They pass directly to the M. subscapularis but before reaching 

 it they divide into numerous branches which diverge somewhat like the 

 rays of a fan. 



