THE ANTERIOR PART OF THE NECK 147 



internal laryngeal nerve enter the pharynx. It is supplied by 

 a twig from the hypoglossal nerve. It approximates the hyoid 

 bone to the thyreoid cartilage. 



Dissection. The dissectors of the head and neck should now 

 proceed to study the relations of the common carotid and sub- 

 clavian arteries, the cervical part of the thoracic duct, and the 

 dome of the pleura, before those structures are disturbed by the 

 dissectors of the thorax. Whilst this is being done, the omo- 

 hyoid must be retained in position, but the upper and lower 

 portions of the other infra-hyoid muscles may be turned upwards 

 and downwards respectively. 



Remove the remains of the fascial sheath from around the 

 common 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, and in an anterior plane. 



After the lower parts of the cervical portions of the vagi have 

 been cleaned, look for the terminal part of the thoracic duct, on 

 the left side, and for the right lymph 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 forwards ; 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 commencement of the innominate vein. 

 On the right side, look for the right lymph 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. Displace 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 lobe of the thyreoid gland, and downwards to the 

 subclavian artery. 



Arteria Carotis Communis. The common carotid artery 

 arises differently on the two sides. On the right side, it arises 

 as a terminal branch of the innominate artery, behind the 

 sterno-clavicular joint ; on the left side, it springs 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, backwards, and slightly laterally to the level of 

 the upper border of the thyreoid cartilage, which lies opposite 

 the fibre-cartilage between the third and fourth cervical 



in 1 a 



