TOPOGRAPHY OF THE THORAX AND ABDOMEN 35 



right (Plate IX). A little higher up, at the level of the 

 fifth vertebra (Plate VIII), the left auricula has been re- 

 placed by the pulmonary artery, the left auricle by the 

 right branch of the pulmonary artery, and the right auri- 

 cle by the right auricula and vena cava superior. The 

 remainder of the ascending aorta and the aortic arch are 

 separated from the sternum and the left lung by large me- 

 diastinal lymph glands. The vena cava lies to the right 

 of the ascending limb of the arch and is separated from it 

 by the pericardium only (Plate VIII). The arch of the 

 aorta is fitted closely around the left side of the trachea. 

 The descending aorta is between the trachea and oesopha- 

 gus internally and the internal surface of the left lung ex- 

 ternally. The left bronchus passes under the arch of the 

 aorta in contact with its concave surface and separates the 

 descending limb from the pulmonary artery and the upper 

 part of the left auricle. At the level of the fifth thoracic 

 vertebra the oesophagus lies to the right of the aorta. It 

 becomes gradually anterior to the aorta and crosses the 

 artery in front of the ninth vertebra to reach the cardia 

 of the stomach. The aorta makes a slight groove in the 

 left lung posterior to the hilus but does not make an im- 

 pression upon the lung near the base. The crura of the 

 diaphragm cover the artery from the upper part of the 

 tenth thoracic to the middle of the first lumbar vertebra, 

 where the aorta pierces the diaphragm and comes into re- 

 lation with the posterior surface of the pancreas. Just be- 

 low the inferior border of the pancreas the artery is crossed 

 by the left renal vein. At the level of the second lumbar ver- 

 tebra the aorta passes behind the transverse portion of the 

 duodenum. Below the duodenum the radix of the mesen- 

 tery is attached to the posterior body wall over the aorta. 

 From the arch to the disc between the first and second 



