928 THE RESPIRATORY SYSTEM. 
The cervical eul de sae of pleura is strengthened and held in place by an aponeurotic 
expansion, first described by Sibson, which is spread over it, and is attached to the inner 
concave margin of the first rib. This fascia is derived from a small muscular slip which 
takes origin from 
the transverse pro- 
cess of the seventh 
cervical vertebra. 
Right vagus nerve. Trachea (Esophagus Left subclavian artery 
: ~ Suleus subclavius 
Right subclavian 
artery 4 
/ Left vagus nerve 
Right 7% 
Left common dl h e cost al 
oe: carotidartery pleura is the 
seat Ae i » | pi My Minne, strongest and 
W/ ) thickest part of 
Zs the parietal 
pleura. It lines 
the deep surface 
of the costal 
arches and of the 
intervening in- 
tercostal muscles. 
Infrontitreaches 
the back of the 
sternum, whilst 
behind )1t)a8 
sarried forwards 
on the bodies of 
the vertebrae. It 
is easily detached 
from the parts 
which it covers, 
except asit passes 
from the heads 
of the ribs on to 
the vertebral 
column. Here it 
is somewhat 
tightly bound 
down. 
The diaphragm- 
atic pleura covers 
the portion of 
the upper surface 
of the diaphragm 
which hes to the 
outer side of the 
base of the peri- 
Fic. 628.—DissEcTion OF A SUBJECT HARDENED BY FORMALIN-INJECTION, to show the cardium, but it 
relations of the two pleural sacs as viewed from the front. The anterior and does not dipdown 
diaphragmatic lines of pleural reflection are exhibited by black dotted lines, whilst 
the outlines of the Iungs and their fissures are indicated by the blue lines. 
we walle 
to the bottom of 
the narrow in- 
terval between the thoracic wall and the diaphragm. In other words, a strip of the 
upper surface of the diaphragm adjoining its costal attachment is left uncovered, 
The mediastinal pleura extends backwards from the posterior surface of the 
anterior thoracic wall to the vertebral column, and it clothes the side of the 
mediastinum or partition intervening between the two pleural cavities. It 1s 
continuous with the pleura costalis of its own side, both in front and behind, along 
two lines which are respectively termed the anterior and posterior lines of pleural 
reflection; whilst below it becomes continuous with the diaphragmatic pleura of 
its own side at the base of the pericardium. 
Above the level of the root of the ling the mediastinal pleura passes directly 
backwards from the sternum to the vertebral column. In this region the J/eft 
