THE PLEURA. 195 



The top of the pleura does not project into the neck in the form of a cone, but 

 resembles a drum-head, being stretched in the form of a plane almost or quite 

 level with the top of the first rib. Its upper surface is strengthened by fibres from 

 the deep fascias of the neck and, according to Sibson, by some fibres from the 

 scalene muscle. 



The pleura then slopes forward behind the sternoclavicular joint to meet the 

 pleura of the opposite side at the level of the second costal cartilage, a little to the left 

 of the median line. They then descend until opposite or a little below the fourth 

 costal cartilage, when they each diverge toward the side, reaching the upper border 

 of the seventh costal cartilage near its sternal junction. They then slope down and 

 out, reaching the lower border of the seventh rib in the mammary line, the ninth rib 



FIG. 214. Anterior surface relations of the lungs and pleurae. 



in the axillary line, and the twelfth rib posteriorly (Joessel and Waldeyer, page 51). 

 The scapular line intersects the lower edge of the pleura at about the eleventh rib. 



In operations involving the lumbar region, if the incision is carried high up 

 posteriorly the pleura may be opened along the lower border of the posterior 

 portion of the twelfth rib. It soon recedes from the costal margin and in the 

 axillary line is about 6 cm. (2! in.) above it. 



A heavy body, as a bullet, gravitates to the lowest portion of the pleural cavity, 

 hence it can be removed through an incision in the eleventh interspace posteriorly. 



( Paracentesis and empyema will be alluded to after the lungs have been 

 described, see p. 200). 



