THE THORACIC CONTENTS 505 



When it is necessary to resect one of the lower ribs, the 

 position of the lower limit of the pleural sac (p. 509) and the 

 fact that the costo-diaphragmatic recess may be obliterated by 

 adhesions must be remembered. Otherwise the diaphragm 

 may be divided and the peritoneal cavity opened. 



The same method of approach may be employed when a rib 

 is the site of tuberculous disease. As much of the infected bone 

 and of the periosteum on the outer surface is removed as may 

 be necessary, but the periosteum on the internal surface, after 

 being carefully scraped, is left otherwise intact and the skin 

 wound is then closed. 



When the lung has been collapsed for some time in the 

 presence of a chronic empyaema, extensive resection of ribs 

 (Estlander, Schede, and Kocher) may be performed to allow 

 the chest wall to fall in and obliterate the persistent cavity. 



A large semilunar incision is made over the lateral aspect of 

 the chest so that its lowest part corresponds to the bottom of 

 the cavity. The anterior extremity of the incision may extend 

 upwards to the lower border of the pectoralis major, and its 

 posterior extremity may ascend between the vertebral border 

 of the scapula and the vertebral spines. In the latter case, the 

 latissimus dorsi, the trapezius, and the rhomboids are all divided. 

 The U-shaped flap thus marked out consists of all the soft parts 

 down to the ribs. When it is retracted upwards, portions of 

 the second to the eighth or ninth ribs may be resected from 

 their angles to their costal cartilages. The periosteum and the 

 thickened parietal pleura are also removed so that the chest 

 wall may be able to fall in upon the collapsed lung. 



In certain cases the lung may be decorticated of its thickened 

 visceral pleura in the hope that it may be able to re-expand. 



THE THORACIC CONTENTS. 



The Pleurae. Each lung is enclosed in a serous membrane, 

 termed the pleural sac. The pleural membrane consists of a 

 visceral layer, which is closely adherent to the lung and lines 

 the fissures in its substance, and a parietal layer. The two 

 pleural sacs are separated from one another by the mediastinal 

 space, which contains the heart, the great vessels, the trachea, 

 the oesophagus, etc., and those parts of the pleural membrane 



