Fig. 71. Course of the Main Vessels and Nerves to the Arm. 



The head is turned to the left, the arm drawn downwards, slightly abducted 

 and rotated outwards. The Platysma and the clavicular portion of the Pecto- 

 ralis Major have been removed. A piece has been excised from its sternal 

 portion, its origin and insertion being thrown inwards and outwards respectively. 



Between the clavicular portion of the Pectoralis Major which usually arises 

 from the inner half of the Clavicle, and the origin of the Deltoid from the outer 

 third of that bone, a A space is left in which the Cephalic Vein disappears to 

 join the Subclavian Vein (for further details cf. Fig. 76, text). 



The Subclavian Vein, Artery and Brachial Plexus pass under the 

 Clavicle (as if it were a bridge!) from the neck into the Axilla. The Vein, sepa- 

 rated from its Artery on the ist rib by the Scalenus Anticus Muscle, lies on its 

 inner aspect, lower down. Externally, and partly behind the artery is the Brachial 

 Plexus which soon surrounds this vessel. The Neuro- Vascular bundle is almost 

 completely covered by muscles, even when the latter are ill-developed. Proceeding 

 directly backwards, without interfering with the muscles, separation of the 

 clavicular portion of the PectoraUs Major from its origin, is necessary. 



The following surface marking can be used for ligature of the Subclavian 

 Artery in this region. Take the midpoint of the Clavicle; the arterj' lies at a 

 finger's breadth interval from this point. 



Above the upper border of the Pectoralis Minor, the Subclavian Artery gives 

 off two branches which are not shewn in our figure: the Acromio-Thoracic and 

 the minute Alar Thoracic (Thoracica Suprema). The anterior Thoracic Nerves which 

 supply the 2 Pectoral Muscles run with the former vessel. They perforate the 

 costo-coracoid membrane. 



Lastly, we mention that in our figure — and this is not uncommon — 

 there is a gap between the sternal and the clavicular portions of the Sterno-Cleido- 

 Mastoid Muscle in which the Internal Jugular Vein is visible. 



