THORACIC CAVITY 21 



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 called the pulmonary 

 ligament (O.T. ligamentum latum pulmonis). The ligament 

 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 they 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 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 the dissector has satisfied 

 himself regarding the nature and the attachments of the 

 pulmonary ligament, he should trace the pleura in the 

 horizontal 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 backwards along the surface of the medias- 

 tinal septum, from the sternum anteriorly to the vertebral 

 column posteriorly, and thence laterally and forwards 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 dis- 

 sector 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 forwards, across the concave base, to the anterior border. 

 By doing this the dissector will again demonstrate to himself 

 the fact that the lung is ensheathed in visceral pleura. Next, 

 placing his fingers on the inner surface of the parietal pleura 

 behind the costal cartilages, he should carry them upwards 

 towards the head, and he will find that they pass upwards into 

 the root of the neck for a distance of from one to two inches 

 above the level of the anterior part of the first rib, but, on 

 account of the oblique position of the rib, only to the level of 

 ii 2 b 



