22 



THORAX 



its neck posteriorly. The apex of the sac, therefore, lies in 

 the root of the neck, and by carefully palpating its inner 

 surface the dissector will be able to distinguish the subclavian 

 artery, which passes across its anterior surface below the highest 

 point, and, possibly, he may be able to locate the internal 

 mammary and costo-cervical arteries (O.T. superior inter- 

 costal) (Fig. 6). The first descends from the subclavian trunk 

 anterior to the apex of the sac, and the second passes first 



Sternum 



Discus articularis 

 Clavicle 



Internal mammary 

 artery 



Innominate artery 

 Right innominate 

 vein 



Trachea 



Right vagus 

 Right recurrent 

 nerve 



First thoracic sym- 

 pathetic ganglion 

 Superior intercostal 

 artery 



Third thoracic 

 vertebra 



Second intercostal 

 nerve 



First rib 



Phrenic nerve 



Right subclavian 



vein 



Right vertebral vein 



Ansa subclayia 



Right subclavian 



artery 



Eighth cervical ; 

 nerve * 



Anterior branch of t. 

 first thoracic nerve 



Anterior branch of 



second intercostal 



nerve 



Lateral branch of 



second intercostal 



nerve 



Cut lower edge of >- 

 pleura 



Third rib 



FIG. 6. Structures in relation with the apex of the pleural sac, 

 seen from below. 



upwards to the apex and then backwards above it. After the 

 dissector has examined the position and relations of the 

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

 just lateral to the line of the vertebral column. It 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 forwards on to 

 the diaphragm and over its surface to the anterior wall of the 

 thorax. If the dissector carries out the examination of the 



