Fig. 117. Boundaries of Lungs and Pleurae from behind. 



The Median Boundaries of the Pleurae posteriorly, i. e. the lines at which 

 the Costal Pleurae become continuous with the Mediastinal Pleurae, run along the 

 bodies of the Vertebrae. The lower limit, i. e. where the Costal Pleura becomes 

 continuous with the Diaphragmatic Pleura, is very important. From the lower 

 border of the 12th Dorsal Vertebra this line runs horizontally outwards so that 

 not only the lower rib cartilages but also the bony ribs are free. The 12th rib, 

 which varies much in length and may even be absent, is usually bisected b}- 

 this line. 



The difference on the two sides in the Axillary Line has been mentioned 

 in Fig. 1 1 6. 



The Apices of the Pleurae are not visible from behind, because they never 

 pass up as high as the upper surface of the ist Dorsal Vertebra. 



The fissures between the Upper and Lower Lobes are indicated by black 

 lines, beginning behind in the 3rd intercostal space they run obliquely outwards 

 and downwards. 



But on the right side a small fissure arises from the main fissure and 

 divides the upper lobe into two — (the Superior and Middle I^obes). 



