THE ANTERIOR PART OF THE NECK 245 



carotid artery and the adjacent part of the internal jugular vein. Separate 

 the vein from the artery and clean the portion of the vagus nerve which 

 lies between them on a posterior plane. Note that on the right side the 

 nerve crosses the anterior surface of the subclavian artery, and there gives 

 off its recurrent branch ; and that on the left side it lies medial to the sub- 

 clavian artery on an anterior plane. 



After the lower parts of the vagi have been cleaned, look for the terminal 

 part of the thoracic duct on the left side and for the right lymphatic duct on 

 the right side. In seeking for the thoracic duct pull the lower end of the 

 left internal jugular vein aside and displace the common carotid artery 

 anteriorly ; then look for the duct as it turns laterally from the border of 

 the oesophagus a little below the level of the cricoid cartilage ; trace it 

 posterior to the internal jugular vein to its termination in the commence- 

 ment of the innominate vein. On the right side look for the right lymphatic 

 duct entering the innominate vein in the angle of union of the internal 

 jugular and subclavian veins. Next look for the cervical portion of the 

 sympathetic trunk, which descends posterior to the common carotid. Clean 

 the nerve trunk carefully and clean also the inferior thyreoid artery, which 

 crosses anterior or posterior to it, at the level of the cricoid cartilage. Dis- 

 place the common carotid laterally, and in the angle between the borders 

 of the trachea and the oesophagus find the recurrent branch of the vagus ; 

 trace it upwards to the point where it disappears under cover of the lateral 

 lobe of the thyreoid gland, and downwards to the subclavian artery. 



Arteria Carotis Communis. The common carotid arises 

 differently on the two sides. On the right side it springs 

 from the termination of the innominate artery, behind the 

 sterno-clavicular joint, and on the left side from the aortic 

 arch in the superior mediastinum. The left artery ascends 

 to the back of the left sterno-clavicular articulation. From 

 the sterno-clavicular joint each common carotid artery runs 

 upwards, posteriorly, and slightly laterally to the upper border 

 of the thyreoid cartilage, which lies opposite the disc 

 between the third .and fourth cervical vertebrae ; and there it 

 ends by dividing into its two terminal branches the internal 

 and the external carotid arteries. 



Superficial Relations. Above the level of the anterior 

 belly of the omo-hyoid the common carotid artery is covered 

 by the skin, the superficial fascia and the platysma, the deep 

 fascia and the anterior margin of the sterno-mastoid. It is 

 crossed immediately above the omo-hyoid by the sterno- 

 mastoid branch of the superior thyreoid artery and, at a higher 

 level, by the superior thyreoid vein ; and it is overlapped by 

 the anterior margin of the internal jugular vein. In the 

 lower part of its extent it lies more deeply : its superficial 

 relations are the skin and superficial fascia, the deep fascia 

 and the sterno-mastoid; the anterior jugular vein, crossing 

 transversely, deep to the sterno-mastoid and above the upper 



