REGION OF THE CAROTID ARTERIES. 85 



the superior cervical ganglion of the sympathetic, and 

 deeper down upon the spinal column the attachments of 

 the rectus anticus major, scaleni, levator anguli scapulae, 

 and splenius colli muscles. Next is the crossing of the 

 omo-hyoid, and in the inferior third from within outward, 

 are the outer borders of the sterno-hyoid and thyroid 

 muscles, covered by their aponeuroses, with the nerves 

 supplying them. Posteriorly and externally are the 

 scaleni and the cervical plexus, the phrenic branch of 

 which lies on the anterior scalenus, behind which is the 

 third part of the subclavian artery, having the ascending 

 cervical artery lying parallel and internal to it ; a quan- 

 tity of lymphatic ganglia, and, inclosed in their proper 

 sheath, lying obliquely, in the middle of this space, the 

 common carotid artery and the internal jugular vein 

 which joins the subclavian vein below; into the junction 

 of which pass, on the right side, the common lymphatic 

 trunk, and on the left the thoracic duct with its tribu- 

 taries. Posteriorly, are the vagus and the recurrent 

 laryngeal nerves, and closer down on the spine the cord 

 of the sympathetic and the middle cervical ganglion, 

 lying on the prevertebral aponeurosis. Posterior to the 

 carotid vessels and below, is that portion of the subelavian 

 artery which lies internal to the anterior scalenus. This 

 vessel, on the right side, arises from the innominate, and 

 lies immediately behind the inferior angle of the diver- 

 gence of the sternal and cleidal origins of the cleido- 

 mastoid, and is separated from the sterno-clavicular ar- 

 ticulation and origins of the sterno-hyoid and thyroid 

 muscles, by the junction of the internal jugular and sub- 

 clavian veins. The vagus and phrenic nerves lie in front 

 of it, with numerous branches of the sympathetic ; whilst 

 embracing it, and passing behind it, is the recurrent 



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