1088 



THE EESPIEATORY SYSTEM. 



sternal reflection-line passes into the right diaphragmatic reflection -line. Opposite the 

 sternal attachment of the fourth costal cartilage the reflection-line of the left pleura 

 deviates laterally, and is continued downwards at a variable distance from the right 

 pleura. A small triangular area of pericardium is thus left uncovered by pleura, and 

 therefore in direct contact with the ventral chest-wall. Leaving the sternum, the re- 

 flection-line of the left pleura passes downwards, parallel and close to the left margin 

 of the sternum, dorsal to the fourth intercostal space, the fifth costal cartilage and the 



fifth intercostal 

 space, to the sixth 

 costal cartilage. 

 There it turns later- 

 ally and downwards, 

 and passes into the 

 diaphragmatic re- 

 flection-line of the 

 left side. 



From the back 

 of the sternum the 

 right pleura is re- 

 flected, in the supe- 

 rior part of the 

 chest, on to the re- 

 mains of the thymus, 

 the right innominate 

 vein and the vena 

 cava superior, and, 

 at a lower level 

 directly on to the 

 ventral aspect of the 

 pericardium. The 

 left pleurais reflectec 

 from the back of the 

 manubrium sterni on 

 to the left innomin- 

 ate vein and the 

 aortic arch, and, at a 

 lower level, directly 

 on to the ventral side 

 of the pericardium. 

 The diaphragm- 

 atic line of reflection 

 is that along which 

 the pleura leaves the 

 thoracic wall and is 

 reflected on to the 

 thoracic surface 

 the diaphragm. This 

 reflection takes place 

 along a curved line, 

 which, except as it 

 approaches the ver- 

 tebral column, is 

 placed a short dis- 

 tance above the in- 

 ferior border of the thoracic wall. It differs somewhat on the two sides of the body. 



On the left side the diaphragmatic line of reflection proceeds downwards along the 

 ascending part of the sixth costal cartilage, crosses the ventral end of the sixth intercostal 

 space and the descending part of the cartilage of the seventh rib (Fig. 865). Still c 

 tinuing to pass downwards, it crosses the eighth costal arch at the junction between 

 cartilaginous and bony portions. This is a fairly constant relation on both sides of 

 the body, and it should be noted that a vertical line the mamillary line, drawn 

 downwards from the nipple of the breast, intersects the line of pleural reflection, close tc 

 the point where it presents this relation to the eighth costal arch. Beyond that point 



FIG. 866. DISSECTION OF THE PLEUIIAL SACS FROM BEHIND. 

 The blue lines indicate the outlines and the fissures of the lungs. 



