1094 



THE EESPIEATOEY SYSTEM. 



costal sinus, but even after the deepest breath it never reaches the extreme lower 

 limit of this recess. 



The diaphragmatic surfaces of the lungs establish important relations with certain of 

 the viscera which occupy the costal zone of the abdominal cavity, the diaphragm alone 

 intervening. Thus the diaphragmatic surface of the right lung rests upon the right 

 lobe of the liver ; whilst that of the left lung is in relation to the left lobe of the 

 liver, the fundus of the stomach, the spleen, and in some cases to the left colic flexure. 



The costal surface is extensive and convex. It is accurately adapted to that 

 part of the wall of the pleural cavity which is formed by the costal arches and 

 the intervening intercostal muscles, and it presents markings corresponding to 

 these. Thus the imprint of the ribs appear as shallow oblique grooves, while the 



intercostal spaces show 

 as elongated intervening 

 bulgings. 



The mediastinal sur- 

 face presents a smaller 



*ppB r rrar,np,ai area 

 Groove for first rib 



Groove for right subclavian artery 



Groove for inferior end of. 

 internal jugular vein J 



O3sophageal area 

 Tracheal area 



Groove for superior . 

 vena cava.* 



Groove for 

 ascending aorta 



Groove for 

 azygos vein 



Depression 



for right 



atrium 



area than the costal sur-. 

 face. It is applied to 

 the mediastinal septum, 

 and presents markings in 

 accordance with the in- 

 equalities upon this (Figs. 

 870 and 871). Thus it is 

 deeply hollowed out in 

 adaptation to the peri- 

 cardium upon which it 

 fits. This pericardial 

 concavity comprises the 

 greater part of the medi- 

 astinal surface, and owing 

 to the greater projection 

 of the heart to the left 

 side, it is much deeper 

 and more extensive in 

 the left lung than in 

 the right lung. Above 

 and dorsal to the peri- 

 cardial hollow is the hilum 

 of the lung. This is a 

 wedge - shaped depressed 

 FIG. 871. THE MEDIAL SURFACE OF A RIGHT LUNG HARDENED /,v SITU, area, within which the 



blood-vessels, nerves, and 



lymph vessels, together with the bronchus, enter and leave the organ. Amidst 

 these structures there are also some bronchial glands. The hilum is surrounded by 

 the reflection of the pleura from the surface of the lung on to the pulmonary 

 root. Dorsal to the hilum and pericardial area there is on each lung a narrow 

 strip of the mediastinal surface of the lung which is in relation to the lateral wall 

 of the dorsal mediastinum. On the right lung this part of the surface is depressed, 

 and corresponds to the oesophagus ; on the left lung it presents a broad longitudinal 

 groove, which is produced by the contact of the lung with the thoracic aorta, and 

 also, close to the base, a small flattened area ventral to this which is applied 

 the oBSophagus where it pierces the diaphragm. 



The portion of the mediastinal surface of the lung which lies above the hili 

 and pericardial hollow is applied to the lateral aspect of the superior mediastinui 

 and the markings are accordingly somewhat different on the two sides. On the 1 

 lung a broad deep groove, produced by the aortic arch, curves dorsally above 1 

 hilum, ajid becomes continuous with the aortic groove on the dorsal part of 

 mediastinal surface. From the groove for the aortic arch a narrower, deeper, anc 



