THE BRACHIAL PLEXUS 287 



and the nerve has for that reason been called the "internal respira- 

 tory nerve of Bell." (Sir Charles Bell was a famous anatomist in 

 former times.) 



The brachial plexus. This plexus is so named because most 

 of its branches supply muscles of the upper extremity (including 

 the shoulder) and those connected with it. 



First important branch, given off in the neck the long thoracic. 

 It passes downward along the side of the thorax to supply the an- 

 terior serratus muscle (p. 102). This muscle is used in forced res- 

 piration and the nerve has been called therefore the "external 

 respiratory nerve." 



The greater part of the branchial plexus is situated in the 

 axilla; most of its branches are given off there 



f supraspinatus 

 Branches: Suprascapular, to < * 



( infraspinatus 



Three large cords: Lateral, medial, posterior. 

 Branches of the cords: 



From lateral cord: Thoracic, to pectoral muscles. 



Musculo-cutaneous, to biceps and brachialis (and 



their integument). 

 Upper root of median nerve. 

 From medial cord: Lower root of median nerve. 



Thoracic, to pectoral muscles. 

 Cutaneous, to integument of forearm. 

 Ulnar, to ulnar muscles. 



( subscapularis, teres major, 

 From posterior cord: Subscapular to I latissimus dorsi (the long sub- 



{ scapular). 



Axillary, to deltoid and teres minor. 

 Radial, to posterior of forearm and hand. 



The three large nerves derived from the brachial plexus are: 



The ulnar from the medial cord. 



The median from the medial and lateral cords. 



The radial from the posterior cord. 



The ulnar nerve runs downward in the medial side of the arm, 

 passes behind the medial epicondyle into the forearm, and ends 

 in the palm (Fig. 183). 



In the forearm it supplies: Flexor carpi ulnaris. 



Flexor digitorum (profundus) partially. 

 In the hand it supplies: Interossei. 



Little finger muscles. 



Thumb muscles (one and a half). 



