THORACIC CAVITY 23 



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 during its 

 development, 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, down- 

 wards, beyond the margins of the aperture of invagination ; 

 the position of the aperture being 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 forwards, 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 thin layer of pleural fluid, and the margins of the lungs 

 enter the sinuses during inspiration and recede from them 

 during expiration. 



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 the size 

 and the form of the organs will then be obtained, and a demonstration 

 will be afforded of their high elasticity, and of their connection with the 

 wind-pipe. 



Dissection. After the dissector has completed the general 

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

 anterior margin of a 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 lung. 

 The lung, thus set free, is to be removed from the thorax, wrapped 

 in a cloth damped with preservative solution, and placed aside 

 for future study. The opposite lung must be removed in a 

 similar manner, and then the margins of the pleural sacs must be 

 examined and their positions, relative to the chest wall, must be 

 noted. 



When both lungs have been removed the dissector should 



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