1 6 THORAX 



apex of the sac he should follow its posterior wall downwards, 

 just lateral to the line of the vertebral column, and, if he is 

 dealing with a subject in good condition, he will find that he 

 can pass his fingers downwards to the lower border of the 

 twelfth rib, where they will be carried anteriorly on to the 

 diaphragm and over its surface to the anterior wall of the 

 thorax. If the dissector carries out the examination of the 

 pleural sac in a thorough manner, and if he has appreciated 

 the significance of the arrangements found at different levels, 

 he will have repeatedly convinced himself that the lung, 

 carrying the blood vessels and air tube with it, has invaginated 

 a portion of the lower part of the medial wall of the pleural 

 sac, and has then expanded anteriorly, posteriorly, upwards and, 

 to a certain extent, downwards beyond the margins of the 

 aperture of invagination, whose position is indicated by the 

 root of the lung and the line of attachment of the pulmonary 

 ligament. The portion of the wall of the pleura which is 

 invaginated by the lung is represented by (i) the visceral 

 pleura, (2) the layers covering the root of the lung, and (3) 

 the pulmonary ligament. 



Before each lung is removed the dissectors should note 

 that its anterior margin does not extend so far anteriorly, and 

 the inferior margin does not extend so far downwards, as the 

 corresponding part of the pleura. The portions of the 

 pleura unoccupied by the lung are called the pleural sinuses. 

 The sinus along the anterior margin of the pleura is the 

 costo-mediastinal sinus, and that along the lower margin, the 

 phrenico-costal sinus. The walls of the sinuses are separated 

 by a capillary space filled with pleural fluid, and the margins 

 of the lungs enter into the sinuses and recede from them 

 during inspiration and expiration, respectively. 



In the event of the lungs not having been hardened in situ by formalin 

 injection the dissectors may, with the consent of the dissectors of the head 

 and neck, introduce the nozzle of the bellows into the cervical part of 

 the trachea and inflate the lungs with air. A truer conception of these 

 organs will thus be obtained, and a demonstration will be afforded of their 

 high elasticity, and of their connection with the wind-pipe. 



After the dissector has completed the general examination 

 of the walls of the pleural sac, he should pull the anterior 

 margin of the lung laterally to expose its medial surface, 

 the front of the root and the front of the pulmonary ligament ; 

 then he should divide the root and the pulmonary ligament, 

 from above downwards, close to the medial surface of the 



