THORACIC CAVITY 67 



and subclavian veins, by the right lymph duct; posteriorly by 

 the vertebral vein, and a vein from the first intercostal space ; 

 anteriorly, by the internal mammary vein and sometimes on its 

 medial side by the right inferior thyreoid vein. Identify and 

 clean as many of these tributaries as possible. Next clean the 

 longer left innominate vein, which passes obliquely across the 

 superior mediastinum along the upper margin of the aortic 

 arch. Joining it at its commencement in the angle between the 

 left internal jugular vein and left subclavian vein is the thoracic 

 duct. The left inferior thyreoid vein enters its upper border. The 

 left vertebral vein and a vein from the first left intercostal join 

 it posteriorly near its commencement. The left superior inter- 

 costal vein, the left internal mammary vein, and some small 

 pericardiac and thymic tributaries enter its lower border. The 

 internal mammary and superior intercostal veins have already 

 been identified (see pp. 15, 42) ; the others should now be 

 secured if possible and all should be cleaned. 



Not uncommonly the right and left inferior thyreoid veins unite at the 

 root of the neck to form a common trunk which terminates frequently in 

 the left innominate vein, but it may end in the junction of the two inno- 

 minate veins or in the right innominate vein. 



Venae Anonymse. The innominate vein of each side is 

 formed, posterior to the sternal end of the corresponding 

 clavicle, by the union of the internal jugular and subclavian 

 veins of the same side; and it ends, at the lower border of the 

 right first costal cartilage, by uniting with its fellow of the 

 opposite side to form the superior vena cava. 



The right innominate vein is short and its course is 

 almost vertical (Figs. 15, 27). It is accompanied on its 

 medial side by the innominate artery, on its lateral side by 

 the right phrenic nerve, and posteriorly by the right vagus 

 nerve (Figs. 22, 23, 29). Antero-laterally it is in relation 

 in the thorax with the anterior margin of the right pleura. 



The left innominate vein is much longer than the right. 

 It passes obliquely to the right and downwards, posterior to the 

 upper half of the manubrium sterni ; it lies posterior to the re- 

 mains of the thymus and the lower ends of the sterno-hyoid 

 and sterno-thyreoid muscles, and anterior to the three great 

 branches of the aortic arch and the left phrenic and vagus 

 nerves (Figs. 22, 27, 29). 



Tributaries. (i)The internal jugular vein, (2) the sub- 

 clavian vein, (3) the vertebral vein, (4) the internal mammary 

 vein, (5) the highest intercostal vein, and frequently (6) the 

 inferior thyreoid vein of the same side. In addition, the right 

 innominate vein receives the right lymph duct, or lymph vessels 

 from the head and neck, the upper extremity and the right 



ii 5 a 



