Lung. 131 



sternum ; so that evidently the anterior margin of the left 

 pleura does not agree with the anterior border of the lung 

 in the neighborhood of the fifth and sixth left costal car- 

 tilages (Fig. 6). Nor does it correspond with the in- 

 ferior border of the lung, since the pleura descends lower 

 than the inferior margin of the lung, for the purpose of 

 accommodating the latter in inspiration. The lower bor- 

 der of the pleura may be represented by a line crossing 

 the mammary, the midaxillary and the scapular lines, 

 about the level of the seventh, ninth and eleventh ribs, re- 

 spectively, and terminating, posteriorly, about the level of 

 the twelfth dorsal spine, although, occasionally, it descends 

 as low as the first lumbar spine, in which case there would 

 be danger of wounding it in operative work on the kidney 

 if the lumbar incision were made close up to the last rib. 

 Operative work on the pleura has been dealt with on page 

 120 when discussing operations on the thoracic walls; 

 whereas, on the lung, the operation of pneumotomy may be 

 performed. This means an opening into the lung, for the 

 purpose of evacuating an abscess in its interior, and is per- 

 formed by making an incision down to the pleura, as in 

 thoracotomy, and then, with a trocar and. canula, seeking 

 for the pus which, if found, should be evacuated and the 

 channel then enlarged by means of a pair of forceps. 



