THE AXTERIOR LIMB 263 



region and in the female the mammary glands (pp. 221 



and 223). 

 (e) The circumflex arteries of the head of the humerus. See 



p. 269. 

 (/) The deep artery (a. profunda brachii). See p. 270. 



The axillary vein (v. axillaris) begins at the medial side of the 

 humerus and crosses the axillary fossa to the first rib whence it is 

 continued as the subclavian. It receives the lateral thoracic and 

 subscapular veins, which accompany the corresponding arteries, 

 and also the cephalic vein (p. 271), which reaches the medial side 

 of the shoulder from the anterior surface of the arm by passing 

 between the teres major and subscapular muscles near the neck of 

 the scapula. 



The brachial plexus (plexus brachialis) is the network of nerves 

 formed from the ventral rami of the posterior five cervical and 

 first thoracic spinal nerves. The cervical nerves also take part in 

 the formation of the more general cervical plexus embracing all 

 nerves of the cervical series. The strands of the brachial plexus, 

 which vary considerably in detail, cross the axillary fossa and at 

 the medial surface of the humerus are largely replaced by the three 

 chief trunks of the free extremity, the radial, medians and ulnar 

 nerves (pp. 271, 272). These nerves are formed principally from a 

 trunk produced by fusion of the ventral branches of the eighth cervi- 

 cal and first thoracic nerves, the latter crossing the inner surface of 

 the first rib to meet the former, but adjacent nerves also contribute. 

 The radial nerve separates first, the median and ulnar a little more 

 distally. 



The seventh cervical nerve gives a branch running mainly to the 

 median and also connecting with the common trunk of the median 

 and ulnar just before it divides into these nerves, and from the same 

 source a slightly larger branch passes to the radial nerve. From 

 the last-mentioned branch a subscapular nerve runs to the teres 

 major, accompanied by a nerve to the latissimus dorsi, which latter 

 frequently receives also a fascicle from the radial nerve. Another 

 subscapular nerve to the muscle of that name arises mainly from 

 the sixth cervical, these two being connected by a loop. A supra- 

 scapular nerve, formed chiefly from the sixth cervical, passes to 



