20 UNIVERSITY OF MISSOURI STUDIES 



root is prolonged downward from the pulmonary vein to 

 the diaphragm, forming the ligamentum pulmonale connect- 

 ing the inner surface of the lung to the mediastinal wall, 

 (Plates XI, XII). 



The hilus of the left lung is shorter and wider than that 

 of the right lung. It extends from the lower border of the 

 fourth to the lower border of the sixth thoracic vertebra. The 

 root structures are in relation anteriorly with the pericard- 

 ium over the left auricle, and posteriorly with the descend- 

 ing aorta and the oesophagus. 



The aorta arches over the root of the left lung and lies 

 in contact with the bronchus and the pulmonary artery. 

 The bronchus, artery^ and vein do not bear the same relation 

 to each other as in the root of the right lung. The bronchus 

 is above at first but in its downward course to pass under 

 the arch of the aorta it also passes behind and below the 

 pulmonary artery. The pulmonary vein lies below the 

 artery but more anterior to it than on the other side. On 

 the right side these structures are bronchus, artery, vein, 

 from above downward ; on this side they are more nearly 

 bronchus, artery, vein, from before backward. On account 

 of the pleural adhesions of this lung, it is difficult to deter- 

 mine the reflections of the pleura over the hilus. 



In the region of the superior mediastinum the right 

 lung is in relation with the trachea and oesophagus, and 

 with the vena cava superior from its formation behind the 

 first sternochondral articulation down to the right auricle. 

 The crista pulmonis projects into the space between the 

 oesophagus and the vertebral column. The vena cava su- 

 perior makes a slight impression upon the lung near the an- 

 terior part of this surface. The innominate artery is in rela- 

 tion with this surface of the lung from the arch of the aorta 



