THORACIC CAVITY 33 



lying in relation with the mediastinal and posterior parts of 

 the costal pleura are satisfactorily completed, the greater part 

 of the pleura should be removed on both sides. 



Dissection. Make a longitudinal incision through the medias- 

 tinal pleura immediately anterior to the phrenic nerve, and a 

 similar incision posterior to the nerve. 



From the anterior longitudinal incision an incision should be 

 carried forwards, at the level of the middle of the root of the lung, 

 and from the posterior longitudinal incision another cut should 

 be carried backwards to the front of the root of the lung and then 

 along its anterior surface. Then the root of the lung should be 

 turned forwards and an incision should be made on its posterior 

 surface parallel with that already made on the anterior surface. 

 This incision should be carried backwards from the root of the 

 lung across the posterior part of the wall of the mediastinum, 

 and then laterally, across the posterior wall of the thorax. 

 When the incisions are completed four flaps will be marked out, 

 two anterior and two posterior. 



The upper anterior flap on the right side must be turned for- 

 wards to the level of the anterior border of the superior vena 

 cava, where it may be cut away, the portion of the pleura extend- 

 ing from the superior vena cava to the sternum being left in 

 situ. The upper anterior flap on the left side should be turned 

 forwards to the anterior part of the arch of the aorta and the 

 anterior surface of the upper part of the pericardium, where it 

 should be cut away, the part extending further forwards to the 

 sternum being left in position. The lower anterior flap on each 

 side must also be turned forwards till the anterior part of the 

 pericardium is reached. There it may be cut away, but the 

 portion of pleura extending from the pericardium to the sternum 

 should not be interfered with at present. 



The posterior flaps on each side should be completely removed, 

 care being taken to avoid injury to any of the structures which 

 they cover. 



After the pleural flaps have been removed the structures 

 which are exposed must be cleaned. 



On the right side commence with the vena azygos, as it 

 arches over the root of the lung ; follow it backwards and then, 

 as far as possible, downwards, raising the right margin of the 

 oesophagus where it overlaps the vein. Then clean the sym- 

 pathetic trunk, which lies along the heads of the ribs, secure the 

 two branches which pass backwards from each of its ganglia 

 to the corresponding intercostal nerve and the branches which 

 pass forwards from the lowest five of the eleven ganglia to form 

 the greater and the lesser splanchnic nerves. Trace the splanch- 

 nic nerves as far downwards as possible. Attempt to find some 

 of the branches which pass from the upper ganglia of the sym- 

 pathetic trunk to the pulmonary plexus on the back of the root 

 of the lung. Then clean the right aortic intercostal arteries and 

 the intercostal veins as they cross the bodies of the vertebrae, 

 and in the posterior parts of the intercostal spaces. The medial 

 parts of the arteries cannot be traced at present. Clean also the 

 branches of the superior intercostal artery which pass to the 

 first two intercostal spaces. Note (i) that all the aortic inter- 

 VOL. II 3 



