BRACHIAL PLEXUS. 415 



Humeral Branches. Descending Branches. 



Superior muscular, External cutaneous, 



Short thoracic, Internal cutaneous, 



Long thoracic, Lesser internal cutaneous / 



Supra-scapular, Median, 



Subscapular, Ulnar, 



Inferior muscular. Musculo-spiral, 



Circumflex. 



The superior Muscular nerves are several large branches which are given 

 off by the fifth cervical nerve above the clavicle ; they are, a subdavian 

 branch to the subclavius muscle, which usually sends a communicating 

 filament to the phrenic nerve : a rhomboid branch to the rhomboidei mus- 

 cles ; and frequently an angular branch to the levator anguli scapulae. 



The Short thoracic nerves (anterior) are two in number ; they arise from 

 the brachial plexus at a point parallel with the clavicle, and are divisible 

 into an anterior and a posterior branch. The anterior branch passes for- 

 wards between the subclavius muscle and the subclavian vein, and is dis- 

 tributed to the pectoralis major muscle, entering it by its costal surface. 

 In its course it sends one or two twigs to the deltoid muscle and gives off 

 a branch which forms a loop of communication with the posterior branch. 

 The posterior branch passes forward beneath the axillary artery and unites 

 \vith the communicating branch of the preceding to form a loop, from 

 which numerous branches are given off to the pectoralis major and pecto- 

 ralis minor. 



The Long thoracic nerve (posterior thoracic, external respiratory of Bell) 

 is a long and remarkable branch arising from the fourth and fifth cervical 

 nerves, immediately after their escape from the intervertebral foramina. 

 It passes down behind the plexus and axillary vessels, resting on the sca- 

 lenus posticus muscle ; it then descends along the side of the chest upon 

 the serratus magnus muscle to its lowest serration. It sends numerous 

 filaments to this muscle in its course. 



The Supra-scapular nerve arises above the clavicle from the fifth cervical 

 nerve and descends obliquely outwards to the supra-scapular notch ; it 

 then passes through the notch, crosses the supra-spinous fossa beneath the 

 supra-spinatus muscle, and passing in front of the concave margin of the 

 spine of the scapula enters the infra-spinous fossa. It is distributed to the 

 supra-spinatus and infra-spinatus muscle. 



The Subscapular nerves are two in number ; of which one arises from 

 the brachial plexus above the clavicle, the other from the posterior aspect 

 of the plexus within the axilla. They are distributed to the subscapularis 

 muscle. 



The Inferior muscular nerves are two or three branches which proceed 

 from the lower and back part of the brachial plexus, and are distributed 

 to the latissimus dorsi and teres major. The former of these is the longer, 

 and follows the course of the Subscapular artery. 



The terminal branches of the plexus are arranged in the following order : 

 the external cutaneous, and one head of the median to the outer side of 

 the artery ; the other head of the median, internal cutaneous, lesser internal 

 cutaneous, and ulnar, upon its inner side ; and the circumflex and mus- 

 culo-spiral behind. 



