THORACIC CAVITY 



45 



noted further that the mediastinum is separated, for descrip- 

 tive purposes, into two main parts, the superior and the 

 inferior mediastinum, by an imaginary plane which passes 

 from the lower border of the manubrium anteriorly to the 



Trachea 

 Vertebral artery 

 Inferior thyreoid artery 

 Transverse cervical artery 

 Trunk common to trans. 



cervical and trans, scap. arts. - M ^ M W ^L^.... ( Trunk of trans, cervical 



( and trans, scap. arteries 



Left common carotid 



Inferior thyreoid artery 

 - Phrenic nerve 



Phrenic nerve -.- 

 Right common carotid 



Right innominate vein ' 



Pericardiac vein 



Internal mammary 

 vessels 



Cut margins of right 

 pleura and of 

 pericardium -- 



Right lung 



Right coronary 

 artery 



Cut margin of 

 right pleura 



Cut margin of 

 pericardium - 



Scalenus anterior 



Left innominate vein 



Internal mammary 

 artery 



Left lung 



Cut margin of 

 left pleura 



Ascending aorta 



Cut margin of 

 pericardium 



Right 

 ventricle 



FIG. 20. Dissection of the Anterior Part of the Thorax. The sternum and 

 costal cartilages were replaced in position after the dissection had been 

 made. The right scalenus anterior is cut away from its insertion up to 

 the level of the upper border of the subclavian artery. 



lower border of the fourth thoracic vertebra posteriorly ; it has 

 been noted also that the inferior mediastinum is separable 

 into three parts: (i) the anterior mediastinum, anterior to the 

 pericardium, (2) the posterior mediastinum, posterior to the 

 pericardium, and (3) the middle mediastinum occupied by the 

 pericardium, the heart, the great vessels immediately adjacent 



