THE LUNGS. 



FIG. 



Groove for 

 subclavian artery 



Groove for 

 innominate vein 



Superior 

 lobe 



Inferior lo 



Left lung, hardened in situ ; antero-lateral aspect. 



heart. As this concavity ends in front, the anterior and 'inferior borders enclose a 

 prolongation of the lung tfowards the median line, known as the lingula. The pos- 

 terior border is variously described. 

 Often the term is applied to the thick 

 mass of lung that fills the region of the 

 thorax along the sides of the vertebrae 

 and the part of the ribs running back- 

 ward. Properly, it is a ridge starting on 

 the inner side of the apex, growing sharp 

 as it descends, but becoming vague and 

 effaced at the lower end. The position 

 of this line is not the same on both sides, 

 nor is it probably always dependent on 

 the same causes. On the left it is more 

 regular, beginning as the posterior bor- 

 der of the groove for the subclavian ar- 

 tery, and continuing as that of the aortic 

 impression until it is lost near the lower 

 border of the lung. Sometimes the be- 

 ginning has no relation to. the subclavian 

 groove, but appears posterior to it, the 

 lung-tissue forming a ridge which enters 

 a little into the space between the front 

 of the spine and the oesophagus, which 

 is here deflected to the left. The line 

 behind the aortic groove lies on the side 

 of the vertebrae, and consequently is the 

 farther back the more the aorta is on the 



side of the column. On the right the posterior border is farther forward, being 

 about opposite the anterior surface of the spine. It may begin as the posterior bor- 

 der of the subclavian groove, or more posteriorly, and continues as a ridge tending 

 to insinuate itself between the spine and the contents of the posterior mediastinum. 

 From just above the root of the lung it is for a short distance continued as the back 

 of the groove for the major 

 azygos vein, below which FIG. 1567. 



it tends to pass between the ^BB^- ^Groove for left subclavian 



oesophagus and the pericar- 

 dium, and finally disappears 

 a little above the lower 

 border. 



The Lobes and Fis- 

 sures. The lungs are di- 

 vided into lobes by deep 

 fissures. The chief fissure 

 starts on the inner aspect of 

 the lung, behind the upper 

 part of the hilum, and as- 

 cends to the posterior sur- 

 face, which it may reach 

 at the same level on both 

 sides, or, as is perhaps more 

 frequent, the right fissure 

 may be one intercostal 

 space lower. The fissure 

 then descends obliquely 

 along the outer aspect of 

 the lung, and reaches the 

 inferior border, where it ends somewhat sooner on the right side than on the left. 

 In the right lung this occurs at the front of the lateral aspect, while it is likely to 



rtery 



Groove for left 



non carotid 

 tery 



.perior pulmo- 

 nary vein 



Lingula 



Diaphragmatic 

 surface 



Preceding lung; median aspect. 



