THE PLEURA. 



1859 



FIG. 1583. 



is continued outward, both before and behind, to become the costal pleura, and is 

 continuous above with the cervical pleura which lines the dome in the concavity of 

 the first rib. It passes below into the diaphragmatic pleura which invests the upper 

 surface of the diaphragm. Laterally, and still more behind, it follows for a certain 

 distance the vertical fibres of the diaphragm, and then is reflected onto the thoracic 

 wall so as to line a potential cavity between the two layers which, except for some 

 little serous fluid, are here in apposition. Villous projections occur along the borders 

 of the lungs, especially at the inferior border, where they form a dense, but very 

 minute fringe, not over i mm. broad. 



Relations of the Pleurae to the Surface. In some places the lungs and 

 the pleurae are always in the same relation ; in others the pleurae extend a certain 

 distance beyond the lungs, which fill them in complete inspiration so that their out- 

 lines correspond ; in other places the 

 pleurae extend so much beyond the lungs 

 that even in the most extreme inspira- 

 tion the latter do not reach the limits of 

 the former. At the apices the relations 

 of the lungs and pleurae are constantly 

 the same, both being in contact. All 

 that has been said of the relation of one 

 to the body-walls is true of the other. 

 Behind the first piece of the sternum the 

 relations are nearly the same, but below 

 this level a space exists in the pleurae 

 into which the lungs enter during deep 

 inspiration. This is notably the case at 

 the left half of the body of the sternum. 

 The pleurae present inferiorly at the sides 

 and behind a merely potential cavity 

 between the diaphragm and the chest- 

 walls, to the bottom of which (probably 

 at the sides and certainly behind) the 

 lungs can never descend. The pleurae, 

 however, never approach closely the 

 lower border of the chest at the sides, 

 for the diaphragm arising from the inner 

 surface of the frame of the thorax takes 

 up a certain amount of space, and above 

 it the connective tissue fills the cleft so 

 that the pleurae do not descend to within 

 3 cm. of the lower border. In the sub- 

 ject used by Hasse the space in the ax- 

 illary line below the reflection of the 

 pleurae to the origin of the diaphragm 

 (the lower border of the chest) was 5.5 cm. on the right and 4 cm. on the left. 



The outlines of the pleurae are as follows. Beginning at the apex, about 3 

 cm. vertically above the cartilage of the first ribs, the anterior borders descend 

 behind the sterno-clavicular joints to meet at the median line at the level of the 

 second cartilage. They then descend together, or nearly so, behind the left half of the 

 body of the sternum. Half-way down the body of the sternum the left pleura tends 

 to diverge to the left, passing from behind the sternum usually at about the junction 

 with the sixth cartilage. The right pleura descends more nearly in a straight line and 

 turns suddenly outward at the level of the seventh cartilage. Laterally the pleurae run 

 pretty close to the cartilages of the sixth rib on the left and the seventh on the right, 

 but both cross the eighth rib at or near the junction of bone and cartilage. In the axillary 

 line, or a little behind it, the pleura crosses the tenth rib at about the same place on 

 both sides, and usually ends posteriorly opposite the lower part of the twelfth thoracic 

 vertebra, the right one being often the lower (Tanja). While such is the general 

 outline, there are considerable and important variations both anteriorly and pos- 



Semidiagramniatic reconstruction, showing relations of 

 left pleural sac (blue) and lung (red) to thoracic wall ; 

 lateral aspect. 



