918 



THE NERVOUS SYSTEM 



thoracic nerves; and (3) the posterior cord, by the posterior branches of all of these 

 cervical nerves. 



The plexus extends from the outer border of the scalenus anterior, where the roots 

 of its constituent nerves appear, to the lower border of the pectoralis minor, where 

 each of its three cords divides into two terminal branches, and it lies in the posterior 

 triangle, in the root of the neck, and in the axillary fossa. In the posterior triangle 

 and the root of the neck it is in relation behind with the scalenus medius (figs. 675, 



FIG. 679. THE BRACHIAL PLEXUS AND BRANCHES OF THE REGION OF THE NECK AND SHOULDER. 

 (After Toldt, "Atlas of Human Anatomy," Kebmaii, London and Ne\v York.) 



lei'sinl j/tijiilnr i ''in 



I'lIllENlC 

 BRANCH TO LEVATOR SCAPl'LM \ 



ANTERIOR BRANCH OF CERVICAL V 



8VTRA8CAPULA& 



! 



VAGUS 



PO S TERIOR\ D RSAL 

 THORACIC \ JOXG THORACIC 



SITRA-CLAVICULAR PORTION OF PLEXPS . 



SUBSCAPI'LMt 

 AXILLARY AXIt 11AIIIAL 

 TWIG TO CORACO-BRACHIALIS \ 

 MUSCULO-CUTANEOUS 1 j 



Sterno-hyoideus 

 and sterno- 

 thyreoidena 



SUBf'l. i i / i v 



--r \MI 



LATI-:I;M, , 

 ANTIISI'.AI'II/M. 

 CUTANEOUS 



J L(>\{; THOKM'ir TO 

 I SKKHATrs AMKKJOS 



\ TIKIKM'O-nOHSM. TO 

 ^ LATIKSIMCS JKJHSI 



afterif 



MED 1. 1 /, A -\TIBRA CHI A L 

 CUTANEOUS 

 MEDIAN 



679). In The posterior triangle it is covered superficially by the skin and superficial 

 fascia, the platysma, the supra-clavicular branches of the cervical plexus, and the 

 deep fascia, and it is crossed by the lower part of the external jugular vein, by the nerve 

 to the subclavius, the transverse cervical vein and the transverse scapular (supra- 

 scapular) vein, the posterior belly of the omo-hyoid muscle, and by the transverse 

 cervical artery. At the root of the neck it lies behind the clavicle and the sub- 

 clavius muscle, and the transverse scapular (suprascapular) artery crosses in front 



