THE HEAD AND NECK 



1093 



fluenced by the position of the shoulder, being greater when the 

 shoulder is raised and carried forwards, and less when it is depressed 

 and carried backwards. 



Contents. — The contents are as follows: (i) the greater portion of 

 the third part of the subclavian artery ; (2) small portions of the 

 transverse cervical artery and vein ; (3) the lower portion of the 

 external jugular vein ; (4) the nerve-trunks of the brachial plexus ; 

 and (5) the nerve to the subclavius muscle, and the supra- 

 scapular and posterior thoracic nerves. 



Third Part of the Subclavian Artery. — ^This part of the vessel 

 extends from the outer border of the scalenus anticus muscle to the 

 outer border of the first rib, where it becomes the axillary artery. 

 Its course is downwards and outwards, and, for the greater part ot 

 its extent, it lies in the subclavian triangle. Subsequently, however, 

 it passes under cover of the clavicle and subclavius muscle. 



Brachial Plexus 



Cephalic Vein \ 



Musculo-cutaneous Nerve 



Deltoid ^ 



Trapezius 



' Suprascapular Vessels 



I \ Transverse Cervical Artery 



Posterior Belly of Omo-hyoid 



Scalenus Anticus 



Stemo<leido-mastoid 



"""••Clavicle in sectioQ 



"~ Subclavius 



■-Axillary Artery 

 ■--Axillary Vein 

 -^Pectoralis Major (cut) 



N«rveofWrisberg , \ \ 

 Axillary Vein ", 

 Ulnar Nerve 



^ Pectoralis Minor 

 Outer Head of Median Nerve 



\ Inner Head of Median Nerve 



Internal Cutaneous Nerve 



Fig. 445. — The Axillary Space, .a.fter Reflection of the Pectoralis 

 Major ; and the Subcl.\vi.\n Tri.\ngle. 



Relations — Anterior. — ^The skin; superficial fascia and platysma 

 myoides ; suprasternal, supraclavicular, and supra-acromial nerves ; 

 deep cervical fascia ; clavicle and subclavius muscle ; transverse 

 cervical vessels ; suprascapular vessels ; nerve to the subclavius 

 muscle ; and the terminal portion of the external jugular vein. 

 The last-named vessel crosses in front of the artery close to the 

 sterno-cleido-mastoid muscle, and in this situation is joined by the 

 transverse cervical and suprascapular veins. A plexiform arrange- 

 ment of veins is sometimes met with over the arteiy, which may be 

 rendered more complex by a branch ascending over the clavicle 



