190 HANDBOOK OF ANATOMY 



anterior surface of the inner side of the forearm as far as the 

 wrist, the other supplies the upper three-fourths of the posterior 

 surface of the inner side. 



Lesser Internal Cutaneous arises from the inner cord of the 

 brachial plexus. It supplies the skin of the upper half of the 

 arm on the inner side. 



Circumflex nerve' from the posterior cord passes down behind 

 the axillary artery and goes through the quadrilateral space in 

 company with the posterior circumflex artery. It winds round 

 the surgical neck of the humerus and ends in the deltoid (see 

 Fig. 6). 



Branches. Muscular to the teres minor and deltoid muscles. 



Articular to the shoulder- joint. 



Cutaneous to the skin over the deltoid and upper half of the 

 arm. 



The Musculo-Spiral nerve is the continuation of the posterior 

 cord of the brachial plexus. It passes through the axilla behind 

 the axillary artery, and down the arm behind the brachial artery 

 on the long head of triceps. It then courses downwards and 

 outwards in the musculo-spiral groove with the superior pro- 

 funda artery, separating the heads of the triceps. The nerve 

 then pierces the external intermuscular septum, and lies in 

 front of the external condyle of the humerus between brachialis 

 anticus and supinator longus, where it ends by dividing into the 

 radial and posterior inter osseous nerves. 



Branches. On the inner side of the humerus : 



1. Internal Cutaneous supplies the skin of the upper third of 

 the inner side of the arm. 



2. Muscular to the three heads of triceps. 

 At the back of the humerus : 



Muscular to the three heads of triceps and anconeus. 



On the outer side of the humerus : 



1. Cutaneous. A superior branch supplies the skin on the 

 outer side and back of the lower third of the arm and the upper 

 half of the back of the forearm. An inferior branch supplies 

 the skin in the upper two-thirds of the back of the forearm on 

 the inner side of the area supplied by the musculo- cutaneous 

 nerve. 





