THE PLEURA. 



603 



FIG. 195. 



form of each pleura is conical, the apex being above, 

 and their relative situation has been compared to that 

 of two bladders placed side by side, so as to leave a space 

 between them. So with the two pleura, they are situated 

 upon either side of the chest, and approach each other 

 along the median line, having a space between them called 

 the mediastinum. This space is divided into an anterior, 

 middle and posterior, and according to some, also a superior 

 mediastinum, 

 each of which 

 contains dif- 

 ferent organs. 

 By commen- 

 cing on the 

 posterior sur- 

 face of the 

 sternum with 

 either the 

 right or left 

 pleura, we 

 trace this 

 membrane to 

 the front of 



the pericardium, thence back to the anterior root of the 

 lungs. From the root it is reflected over the anterior sur- 

 face of the lungs, and traced round upon the posterior sur- 

 face to the back part of the root, whence it is reflected 

 to the posterior pericardium, and back to the sides of the 

 vertebrae. From this latter point the pleura stretches 

 all along the spine, ascending as high as the sixth or 

 seventh cervical vertebra, and as low as the diaphragm, 



Fie. 195 represents the Pleura and its reflections from a transverse section 

 of the chest, a Right lung, b Left lung, c Root of lungs, showing the rela- 

 tion of its vessels. 22 Pulmonary vein. 1 Pulmonary artery. 2 Bronchial 

 tube, d d Reflection of pleura from root of the lung, t Cavity of pleura. 

 / Anterior mediastinum, g Middle mediastinum, containing the heart, h 

 fcavity of the pericardium-, i i Direction of the phrenic nerves, j Aorta, k 

 Vena-azygos. I Thoracic duct, m (Esophagus, w Sympathetic nerve, j k I 

 are in the posterior mediastinum. 



