i 4 THORAX 



portion which is termed the parietal pleura ; all that inter- 

 venes between the two portions being a thin stratum of fluid, 

 sufficient to lubricate the surfaces and prevent friction during 

 the movements of the lung and the chest wall. 



After he has grasped the facts noted above the dissector 

 should follow the inner surface of the pleura in the transverse 

 plane at the level of the fifth costal cartilage, that is, below 

 the level of the root of the lung. At that level he will find 

 that the parietal pleura covering the lateral surface of the 

 mediastinal septum is connected with the visceral pleura on 

 the medial surface of the lung by a thin fold, the pulmonary 

 ligament (O.T. ligamentum latum pulmonis). This consists of 

 an anterior and a posterior layer, which correspond, respectively, 

 with the layers on the front and the back of the root of the 

 lung, but are in contact with each other at the level of 

 the fifth rib, on account of the absence of the great blood 

 vessels and air tube of the lung. The pulmonary ligament 

 extends laterally from the mediastinum to the medial surface 

 of the lung, and from the root of the lung above, to within 

 a short distance from the diaphragm below. Its medial, 

 lateral, and upper borders are attached respectively to the 

 mediastinal septum, the lung, and the lower border of the 

 lung root, and are continuous with the pleura covering each, 

 but its lower border is free. When he has satisfied himself 

 regarding the nature and the attachments of the pulmonary 

 ligament, the dissector should trace the pleura in the hori- 

 zontal plane at the level of the manubrium sterni, that is, 

 above the level of the root of the lung. There he will find 

 that the medial wall of the sac is not reflected on to the lung, 

 but that it passes posteriorly along the lateral surface of the 

 mediastinal septum from the sternum anteriorly to the vertebral 

 column posteriorly, and thence laterally and anteriorly to the 

 sternum in an unbroken circle. In the same way he will 

 be able to trace the visceral pleura in a similar but smaller 

 unbroken circle around the upper part of the lung. 



Having traced the pleura in three horizontal planes the 

 dissector must next trace it in the vertical plane, first around 

 the lung, and then around the wall of the thorax. Commencing 

 with the lung, the fingers should be passed along the anterior 

 border to the apex, thence, down the thick posterior border, to 

 the base, and anteriorly, across the concave base, to the anterior 

 border. By doing this he will again demonstrate to himself 



