36 UNIVERSITY OF MISSOURI STUDIES 



lumbar vertebrae, the thoracic duct lies along the right 

 side of the aorta. The two vessels pierce the diaphragm 

 together. The cisterna chyli lies to the left of the aorta 

 over the second lumbar vertebra. The thoracic duct lies 

 between the aorta and the vena azygos major. The aorta 

 and vena cava inferior are separated near the heart by the 

 oesophagus. After the oesophagus enters the stomach the 

 vessels are separated by the right crus of the diaphragm, 

 down to the aortic opening of the diaphragm. The last 

 5 cm. of the aorta are in direct relation with the left side of 

 the vein. The left vagus nerve lies upon the anteroex- 

 ternal part of the aorta down to the diaphragm. Its re- 

 current laryngeal branch passes between the bronchus and 

 the under surface of the arch on its way back to the larynx. 



The vena cava superior is formed behind the right 

 border of the manubrium at the level of the first sterno- 

 chondral articulation. It descends nearly vertically down- 

 ward to empty into the right auricle at the level of the 

 second intercostal space and the lower part of the fifth thor- 

 acic vertebra. It lies between the ascending aorta and the 

 anterior part of the internal surface of the right lung. It 

 is separated from the sternum by the lung, and passes be- 

 hind the right auricula just before entering the heart. Be- 

 hind the upper part of the vena cava superior is the trachea 

 and behind the lower part, the right branch of the pulmo- 

 nary artery. The right phrenic nervei runs between it and 

 the pleura. 



The vena cava inferior is formed in front of the lower 

 part of the fourth lumbar vertebra a little to the right of 

 the midplane and empties into the posteroinferior part of 

 the right auricle (Plate XII) at the level of the disc between 

 the eighth and ninth thoracic vertebrae. The opening, into 

 the heart, of the vena cava inferior is vertically under that 



