130 Anatomy Applied to Medicine and Sutgery. 



and whether the disease was spreading from one lobe to 

 another or not. 



Landmarks for the Roots of the Lungs. The 

 root of the right lung extends from a point opposite 

 'the lower border of the second right costal cartilage, 

 about half an inch from the right edge of the sternum, to 

 the upper border of the fourth cartilage, the same distance 

 from the sternum, while the root of the left lung corre- 

 sponds to a line drawn from the upper border of the third 

 left costal cartilage, down to the middle of the fourth, at a 

 distance of about one inch from the left border of the 

 sternum. Thus, it will be seen that the root of the left 

 lung is farther away from the sternum than that of the 

 right, and this is due to the projection of the mediastinum 

 to the left side. Further, the left root is on a lower level, 

 i.e., farther down than the right, because of the presence 

 of the aorta which arches over it and displaces it down- 

 wards, so that, while the right bronchus enters the lung at 

 the level of the fifth dorsal vertebra, the left bronchus en- 

 ters at the level of the sixth dorsal vertebra. 



Landmarks for Pleurae. The landmarks for the 

 Pleurtz agree with those for the outlines of the lungs, with 

 the exception of the region of the fifth left cartilage, and 

 along the lower borders. In the region of the fifth left car- 

 tilage there is considerable variation, according to the dif- 

 ferent observers, in the direction of the pleura. Sic& 

 found that, in the majority of twenty-three cases exam- 

 ined by him, the pleura had not left the sternum at the 

 level of the sixth costal cartilage, i.e., that it extended 

 over the cardiac area, and did not follow the margin of 

 the lung. Luschka (Quain) states that, at the level of 

 the fifth cartilage, the pleura is one-twelfth of an inch ; at 

 the sixth, four-fifths of an inch, and at the seventh, one 

 and two-fifths of an inch external to the left border of the 



