THE PLEUK^E. 



1087 



Left innominate vein 



pleura 

 (cut edge) 



vertebral line of reflection is fairly constant, the other two reflection-lines are subject to 

 marked variations in different subjects. Consequently the following description must be 

 regarded as merely giving the average condition. 



The vertebral line of pleural reflection is that along which the costal pleura is 

 continued ventrally from the vertebral column to become the mediastinal pleura. On 

 the right side, above the root of the lung, the pleura passes from the bodies of the 

 vertebrae on to the right 

 side of the trachea ; whilst 

 lower down, and dorsal to 



the pericardium, it passes (Esophagus 



from the vertebral bodies Leftsubcia\ 



on to the oesophagus. On Left common carotid artery *y^Vr^^HBI^M Parietal 



the left side, and above Left superior intercostal vein 



the arch of the aorta, the 

 , pleura along this line of 



reflection is carried from 

 j the vertebral column on 



to the oesophagus and 



thoracic duct ; below that 



level it passes on to the 



thoracic aorta. In the 



superior part of the chest 



the right and left lines 



of reflection are placed 



well apart from each other, 



and about equidistant 



from the median plane. 



As they are traced down- 

 wards they approach more 



closely to each other and 



deviate to the left, so that 



whilst the reflection on the 



right side takes place from 



the ventral aspect of the 



vertebral bodies, on the 



left side it takes place from 



the left aspect of the ver- 

 tebral column. This is \\ ^SKi^ jf / S~~ -/ IBS- -Diaphragm 



due to the position of the 

 ' thoracic aorta. 



The sternal line of 



pleural reflection is that 



along which the costal 

 i pleura leaves the ventral 

 , thoracic wall to become 



the mediastinal pleura. 



The lines differ somewhat 



on the two sides, and in 



both cases show a tend- 

 ency to deviate to the left 



(Fig. 863, p. 1085). In the FlG - 865 - LEFT PLEURAL SAC IN A SUBJECT HARDENED BY FORMALIN 



vicinity of the rr ihrinm INJECTION, opened into by the removal of the costal part of the parietal 



pleura. The lung has also been removed so as to display the media- 



iterni the two pleural sacs stinal pleura. 



are separated from each 



other by an angular interval. The lines of reflection at the superior thoracic aperture or 



inlet correspond to the sterno-clavicular joints. From those points the lines, as they 

 : are traced downwards, converge behind the manubrium, until at last they meet at its 



inferior border. There the two sacs come into contact with each other, and the lines of 

 eflection coincide. Thence they proceed downwards, on the back of the body of 



the sternum, with a slight deviation to the left of the median plane, until a point 



immediately above the level of the sternal attachments of the fourth costal cartilages 

 3 reached, and there the two sacs part company. The line of reflection of the right 



pleura is continued downwards in a straight line to the xiphoid process, where the 



