THE LUNGS. 937 
the right lung the hilus is also circumscribed above by a curved groove, but this 
is narrow and more distinctly curved than the aortic groove on the left side. — It 
lodges the vena azygos major as it turns forwards to join the superior vena cava. 
From the anterior end of the azygos sulcus a wide shallow groove extends upwards 
to the lower part of the front of the apex pulmonis. This is produced by the 
apposition of the lung with the vena cava superior and the right innominate vein. 
Close to the summit of the apex there is also, on its inner aspect, a sulcus for the 
upper end of the innominate artery. 
In addition to the hilus, it must now be evident that the inner surface of each 
lung presents three areas which correspond respectively with (1) the middle 
mediastinum (7.e. the pericardial hollow) ; (2) the posterior mediastinum ; and (3) the 
superior mediastinum ; and that in each of these districts impressions correspond- 
ing to structures contained within these portions of the interpleural space may be 
noticed. 
The posterior border of the lung is thick, long, and rounded. It forms the most 
bulky part of the organ, and oceupies the deep hollowin the thoracic cavity which 
is placed on either side of the spine. Indeed the term “ border” is somewhat in- 
appropriate, as it forms in reality a somewhat extensive surface deeply impressed 
by the ribs, and not in any way marked off from the outer surface of the 
lung. - 
The anterior border of the lung is short and exceedingly thin and sharp. It 
begins abruptly above, immediately below the groove on the apex for the innomi- 
nate vein, and extends down to the base, where it becomes continuous with the 
sharp basal border. The 
thin anterior part of the 
lung is carried forwards ALO LE adit 
and inwards in front of Scalenus medius_ Vis eee ains 
the pericardium into the Brachial nerves. _ E i cee EET 
narrow pleural recess _Subclavius—_ \\ _ -Supra-spinatus 
behind the sternum and cee oe 
_Subscapularis 
Spine of 
costal cartilages (sinus  Subclavian 
5 . : vein aaSGS ls 
costo-mediastinalis). ; itis 
The anterior border of Rib i. Se 
the right lung fills up 
this recess completely, Pectoralis_ 
and in the upper part of es 
the chest 1s only separ- 
ated from the correspond- 
ing border of the left 
lung by the two layers 
of mediastinal pleure 
which are reflected back- 
wards from the sternum 
to the pericardium. The 
anterior border of the 
left lung, in its lower 
part, shows a marked 
deficiency or notch (in- 
cisura cardiaca) corre- 
sponding to the apex of 
the heart, and where this 
exists the lung margin 
leaves a considerable por- 
tion of the pericardium 
uncovered, and fails to 
completely fill up the 
costo-mediastinal sinus of the pleural cavity. During respiration the anterior 
margin of the left lung at the incisura cardiaca advances and retreats to a small 
extent in this pleural sinus in front of the pericardium. 
| __ Fissure of 
the lung 
Root of 
lung 
\/7 TV of pleura 
Pre. 6305 
SAGITTAL SECTION THROUGH THE LEFT SHOULDER, 
LuNG, AND APEX OF THE Heart. 
