

THE THORAX. 327 



Relations. Right : In front, sternal origins of the sterno- 

 hyoid and sternothyroid muscles, clavicle, first costal carti- 

 lage, and remains of the thymus gland ; behind, pleura 

 and lung ; to the right, pleura, lung, and phrenic nerve 

 (right) ; to the left, right subclavian artery and pneumo- 

 gastric nerve, the innominate artery, and trachea. 



The left : In front, sternohyoid and sternothyroid mus- 

 cles, manubrium, clavicle, sternoclavicular articulation, re- 

 mains of thymus gland ; behind, innominate, left carotid 

 and subclavian arteries, trachea, left phrenic nerve, left 

 pneumogastric nerve ; below, the transverse aorta ; above, 

 the cervical fascia and inferior thyroid veins. 



Tributaries. Both receive the internal jugular, subcla- 

 vian, vertebral, deep cervical, and inferior thyroid veins 

 above, and the internal mammary below. The left vein 

 also receives the left superior intercostal, thymic, medias- 

 tinal, pericardiac veins, and the thoracic duct ; the right, 

 the right lymphatic duct. The ducts empty into the in- 

 nominate veins at the junction of the internal jugular and 

 subclavian. 



The Superior Vena Cava. Fig. 70. Diags. 21, 22. 



This is formed in the first intercostal space close to the 

 right side of the sternum by the junction of the right and 

 left innominate veins. Its course is downward to the right 

 auricle of the heart, into which it opens. 



Relations. -In front, first and second intercostal spaces 

 and the second costal cartilage, remains of the thymus 

 gland, pericardium, pleura, and right lung ; behind, azygos 

 major, right bronchus, right pulmonary artery, and right 

 superior pulmonary vein, the pericardium ; to the right, 

 phrenic nerve, lung, and pleura ; to the left, ascending 

 aorta, innominate artery. 



