76 DISSECTION OF THE NECK. 



position beneath the clavicle. This vessel ( 8 ) is derived from the branch- 

 ing of the innominate artery behind the sterno-clavicular articulation, and 

 the part of it named subclavian extends as far as the lower border of the 

 first rib. To reach the limb the artery crosses the lower part of the neck, 

 taking an arched course over the bag of the pleura and the first rib, and 

 between the scaleni muscles. For the purpose of describing its numerous 

 connections the vessel may be divided into three parts : the first extending 

 from the sterno-clavicular articulation to the inner border of the interior 

 scalenus ; the second, beneath the scalenus ; and the third, from the outer 

 border of that muscle to the lower edge of the first rib. 



First part. Internal to the anterior scalenus the artery lies deep in the 

 neck, and ascends slightly from its origin. Between the vessel and the 

 surface will be found the common integumentary coverings with the pla- 

 tysma and the deep fascia, the sterno-mastoid, sterno-hyoid and sterno- 

 thyroid muscles, and a strong -deep process of fascia from the inner border 

 of the scalenus muscle. This part of the subclavian lies over the longus 

 colli muscle, though at some distance from it, and separated from it by fat 

 and nerves. Below the artery is the pleura, which ascends into the arch 

 formed by the vessel. 



Veins. The innominate vein, and the ending of the subclavian ( 7 ), form 

 an arch below that of the artery. The large internal jugular vein crosses 

 the arterial trunk close to the scalenus ; and underneath this vein, with 

 the same direction, lies the vertebral vein. Much more superficial, and 

 separated from the artery by muscles, is the deep part of the anterior jugu- 

 lar vein. 



Nerves. In front of the artery lies the pneumogastric nerve, near to the 

 internal jugular vein ; and inside this, the lower cardiac branch of the 

 same nerve trunk. Behind the subclavian artery winds the recurrent 

 branch of the pneumogastric ; and still deeper is the cord of the sympa- 

 thetic nerve with its cardiac branches, one or more of its offsets entwining 

 round the vessel. 



Second part. Beneath the scalenus the vessel is less deep than when 

 placed internal to that muscle, and at this spot it rises highest above the 

 clavicle. The second part, like the first, is covered by the integuments, 

 platysma, and deep fascia ; then by the clavicular origin of the st ;rno- 

 mastoideus ; and lastly by the anterior scalenus. Behind the vessel is the 

 middle scalenus. Below the artery is the bag of the pleura, which ascends 

 between the scalena. 



Veins. Below the level of the artery, and separated from it by the an- 

 terior scalenus muscle, lies the arch of the subclavian vein. 



Nerves. In front of the scalenus descends the phrenic nerve. Above 

 the vessel, in the interval between the scalena, are placed the large cervical 

 nerves ; and the trunk formed by the last cervical and first dorsal is inter- 

 posed between the artery and the middle scalenus. 



Third part. Beyond the scalenus the artery is contained in the clavicu- 

 lar part of the posterior triangular space (p. 64), and is nearer the surface 

 than in the rest of its course : this part of the vessel is inclosed in a tube 

 of the deep cervical fascia, which it receives as it passes from between the 

 scaleni. It is comparatively superficial whilst in the space before men- 

 tioned, for it is covered only by the integuments, the platysma, and deep 

 fascia ; but near its termination the vessel gets under cover of the supra- 

 scapular artery and vein, and the clavicle and subclavius muscle. In this 



