THE SUPERIOR EXTREMITY 



the platysma, the pectoralis major, the pectoralis minor, the 

 costo-coracoid membrane, the cephalic vein, and the axillary 

 artery; behind it lie the upper serration of the serratus 

 anterior, the fascia -filled interval between the medial and 

 posterior walls of the axilla, and the subscapularis muscle 



(Fig. 22). 



The Branches of the Plexus. The branches from the 

 roots of. the plexus are: (i) Branches to the scalenus 

 anterior, the longus colli, the scalenus medius, and the 

 scalenus posterior (from C. v., vi., VIL, vin.). (2) A com- 

 munication to the phrenic nerve (from C. v., or v. and vi.). 



Levator scapulae 



Dorsal scapular nerve 

 External jugular ve 



Scalenus mediu 

 Transverse cervical artery 



Omo-hyoid muscle 

 Brachial plexus 



Suprascapular 

 nerve 



Sterno-hyoid muscle 



Sterno-mastoid 

 muscle 



Transverse 

 scapular artery 

 Scalenus anterior 

 Subclavian artery 

 Subclavian 



FIG. 21. Dissection of the lower part of the Posterior Triangle of the Neck, 

 showing the Supraclavicular Part of the Brachial Plexus. 



(3) The dorsalis scapulae nerve, which supplies the rhomboid 

 muscles (from C. v.). (4) The long thoracic nerve, which 

 supplies the serratus anterior (from C. v., vi., VIL). 



The branches from the trunks of the plexus are: (i) The 

 nerve to the subclavius, from the upper trunk (from C. v., vi.). 

 It has already been seen piercing the posterior surface of the 

 costo-coracoid membrane and entering the posterior aspect 

 of the subclavius (p. 37). (2) The suprascapular nerve, 

 from the upper trunk (from C. v., vi.). It will be found 

 crossing the lower part of the posterior triangle, deep to 

 the posterior belly of the omo-hyoid muscle, and disappear- 

 ing through the scapular notch on its way to the dorsum 

 scapulae (Fig. 22). 



