1 8 THORAX 



the anterior margin of the right sac continues to descend, still 

 with a slight inclination to the left, till it reaches the xiphoid 

 process, where it becomes continuous with the inferior margin. 

 This turns laterally, passing behind the xiphoid process and 

 the cartilage of the seventh rib ; it then crosses the junction 



Cervical dome of pleura 



Left subclavian artery 



Left common carotid artery 



Left innominate vein 



Internal mam- 

 mary artery 



Anterior margin 



of right 



pleural sac 



Intercostal nerve 



Pericardium 



Transversus tj 

 thoracis 



Diaphragm 



FIG. 7. Diagram to show the parts which lie anterior to the pericardium 

 and heart. The outline of the heart is indicated in red by a dotted line, 

 and the anterior margins of the pleural sacs are represented by blue lines. 



of the bone and cartilage of the eighth rib and reaches 

 the level of the tenth rib in the mid-axillary line; turning 

 posteriorly, it crosses the eleventh and twelfth ribs, and just 

 below the middle of the latter it becomes continuous with the 

 posterior margin, which ascends along the line of the angle of 

 the ribs to the apex. On the left side, at the level of the 

 fourth costal cartilages, the anterior margin of the left pleura 

 turns away from the median plane, for a variable distance, 



