‘ THE PLEURAL MEMBRANES. oa 
parallel and close to the left margin of the sternum behind the fourth intercostal 
space, the fifth costal cartilage and the fifth intercostal space, to the back of the sixth 
costal cartilage. Here it turns outwards and downwards, and passes into the diaphragmatic 
reflection-line of the left side. 
From the back of the sternum the right pleura is reflected in the upper part of the 
chest on to the remains of the thymus, the right innominate vein and the vena cava, and 
below this directly on to the front of the pericardium. The left plewra is reflected from 
the back of the manubrium sterni on to the left innominate vein and the aortic arch, and 
below this directly on 
to the front 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 
upper surface of the 
diaphragm. This 
reflection takes place 
along a curved line, 
which, except behind 
as it approaches the 
vertebral column, is 
placed a short dis- 
tance above the lower 
border of the thoracic 
wall. It differs some- 
what on the two sides 
of the body. 
On the left side 
the diaphragmatic 
line of reflection pro- 
ceeds downwards 
behind the ascending 
part of the sixth 
costal cartilage, 
crosses behind the 
anterior end of the 
sixth intercostal 
space and the de- 
scending part of the 
cartilage of the 
seventh rib (Fig. 
630). Still continu- 
ing to descend, it 
passes behind the 
eighth costal arch at 
the junction between 
its 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 drawn downwards from the nipple (mammillary 
line) intersects the line of pleural reflection close to the point where it presents this 
relation to the eighth costal arch. Beyond this point the line of diaphragmatic 
reflection is carried downwards and outwards across the extremities of the bony portions 
of the ninth and tenth ribs. As it passes under cover of the tenth rib, or it may be as 
it proceeds across the tenth intercostal space, the line of pleural reflection reaches its 
lowest point, and it is important to observe that this point lies in the mid-lateral line (2.€. @ 
vertical line drawn downwards on the side of the chest midway between spine and 
sternum). _ From this it ascends slightly as it curves backwards towards the spine. Thus 
LEFT KIDNEY 
Fic. 631.—DIssecTION OF THE PLEURAL Sacs FROM BEHIND. 
The blue lines indicate the outlines and the fissures of the lungs. 
