234 Branches of Subclavian Artery 



The internal mammary is described on p. 155, and the superior 

 intercostal on p. 157. 



The subclavian vein, the continuation of the axillary, begins at 

 the outer border of the first rib, and joins with the internal jugular 

 behind the sterno-clavicular articulation to form the innominate ; the 

 two innominates eventually join to form the superior vena cava, as 

 shown in the illustration on p. 185. 



Chief relations. The vein lies below and in front of the third 

 part of the subclavian artery, and behind the subclavius muscle and 

 the clavicle. It passes in front of the phrenic nerve and the scalenus 

 anticus, and over the apex of the pleura. 



Its tributaries are the external and anterior (p. 35) jugulars. 



The wall of the vein adheres closely to the fascia! sheath by which 

 it is invested, and, indirectly, to the clavicle and costo-coracoid mem- 

 brane, the vessel being expanded when the shoulder is brought 

 forwards. ' Hence care should be taken in operations about the root 

 of the neck or the shoulder in order to avoid the danger of air being 

 drawn into the circulation by movements of the limb.' (Quain.) If 

 this contingency should arise, the wound should be filled with water 

 whilst the opening in the vein is being sought. 



