io6 THORAX 



whole of the thoracic portion of its course, and arrange with the dissector 

 of the head and neck to display the cervical portion of its course. 



The Thoracic Duct. The thoracic duct is a vessel of 

 small calibre but of great importance, for it conveys, to the 

 left innominate vein, the whole of the lymph from the lower 

 extremities, the abdomen (except that from part of the upper 

 surface of the liver), the left side of the thorax, including the 

 left lung and pleura and the left side of the heart, the left 

 upper extremity, and the left side of the head and neck. It 

 is the upward prolongation of a dilated sac, the cisterna 

 chyli, which lies between the right crus of the diaphragm and 

 the bodies of the first and second lumbar vertebrae. It 

 enters the thorax through the aortic orifice of the diaphragm, 

 lying between the aorta on the left and the vena azygos on 

 the right. It continues upwards through the posterior 

 mediastinum, lying between the descending aorta and the 

 vena azygos, anterior to the right aortic intercostal arteries 

 and the hemiazygos and accessory hemiazygos veins, and 

 posterior to the right pleura below and the oesophagus above. 

 At the level of the fifth thoracic vertebra it crosses to the left 

 of the vertebral column, and then ascends, through the superior 

 mediastinum, along the left border of the oesophagus, in 

 contact, on the left, with the left pleural sac, and separated 

 posteriorly from the left longus colli muscle by the mass of 

 areolar tissue. Anterior to the thoracic duct, in the superior 

 mediastinum, are the termination of the aortic arch, the left 

 subclavian, and the left common carotid arteries, in that order 

 from below upwards. At the upper end of the thorax the 

 thoracic duct enters the root of the neck, and, at the level of 

 the seventh cervical vertebra, it turns laterally, posterior to 

 the left common carotid artery, the left vagus nerve, and the 

 left internal jugular vein, and anterior to the vertebral artery 

 and veins, the thyreo-cervical trunk or inferior thyreoid artery, 

 and the phrenic nerve. Then, turning downwards, anteriorly 

 and medially, on the anterior aspect of the scalenus anterior, 

 it crosses anterior to the transversa colli and transversa scapulae 

 arteries, and terminates in the upper end of the innominate 

 vein, in the angle of junction of its internal jugular and sub- 

 clavian tributaries. Immediately before its termination it 

 receives the left common jugular and subclavian lymphatic 

 trunks, unless they end separately in one or other of the 

 three large veins. When the thoracic duct is distended it 



