34 THORAX 



costal arteries and all the intercostal veins except the first pass 

 behind (external to) the sympathetic trunk (Fig. 13) ; (2) that 

 the two intercostal branches from the superior intercostal artery 

 do not pass behind the sympathetic trunk (Fig. 6) ; (3) that 

 the intercostal vein from the first intercostal space passes up- 

 ward to join the right innominate vein ; (4) that the intercostal 

 veins from the second, third, and sometimes that from the 

 fourth also, join together to form a common trunk called the 

 right superior intercostal vein, which terminates in the vena 

 azygos ; (5) that all the remaining intercostal veins on the right 

 side end directly in the vena azgyos. 



Next clean the right vagus. It descends along the right side 

 of the trachea, passes medial to the arch of the vena azygos, 

 and breaks up, on the back of the root of the lung, into the 

 posterior pulmonary plexus. Look for fine branches which pass 

 from its anterior border to the front of the root of the lung, 

 where they join the anterior pulmonary plexus ; then clean the 

 posterior pulmonary plexus and trace the continuation of the 

 vagus from it to the wall of the oesophagus, but do not follow 

 it further at present. As the posterior pulmonary plexus is 

 being cleaned look for the branches of the right bronchial artery 

 which ramify on the posterior surfaces of the bronchi. Next 

 clean the right side of the trachea from the vena azgyos to the 

 upper aperture of the thorax and the right margin of the 

 oesophagus, which lies posterior to the trachea. Follow the 

 oesophagus as far as the back of the root of the lung, but do 

 not injure the vena azygos. Finally, clean the pericardium and 

 the superior and inferior venae cavae, behind and in front of the 

 strip of pleura left covering the phrenic nerve (Fig. 13). 



On the left side, after the pleural flaps have been removed, 

 clean first the left superior intercostal vein. It runs from behind 

 forwards, obliquely across the aortic arch, superficial (lateral) 

 to the left vagus nerve. Follow it forwards only as far as the 

 strip of pleura which was left in position covering the phrenic 

 nerve. Then follow it backwards, and note that it is formed by 

 the union of the intercostal veins of the first, second, and third 

 intercostal spaces (Fig. 14), unless, as on the right side, the 

 first intercostal vein passes to the innominate vein. Next clean 

 the left sympathetic trunk. Secure the two branches which 

 pass backwards from each of its ganglia to the correspond- 

 ing 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. Follow the splanchnic nerves 

 as far as possible downwards. Attempt to find some of the 

 branches which pass forwards from the upper ganglia to the left 

 posterior pulmonary plexus. Then pull the descending aorta 

 as far forwards as possible, and clean the left aortic intercostal 

 arteries and the accompanying veins and the intercostal branches 

 of the left superior intercostal artery. Note (i) that the upper 

 two intercostal arteries are derived from the superior intercostal 

 artery, and that they do not pass posterior to the sympathetic 

 trunk ; (2) that all the other intercostal arteries and veins pass 

 posterior to (external to) the sympathetic trunk, except the left 

 superior intercostal vein which is formed by the union of three 

 or more intercostal veins after they have crossed the sympathetic 

 trunk ; (3) that the fourth, fifth, sixth, and seventh, and some- 



