1094 



SPLANCHNOLOGY 



tity as age advances, and is more abundant in males than in females. As a rule, 

 the posterior border of the lung is darker than the anterior. 



The right lung usually weighs about 625 gm., the left 567 gm., but much varia- 

 tion is met with according to the amount of blood or serous fluid they may contain. 

 The lungs are heavier in the male than in the female, their proportion to the body 

 being, in the former, as 1 to 37, in the latter as 1 to 43. 



Each lung is conical in shape, and presents for examination an apex, a base, 

 three borders, and two surfaces. 



The apex (apex pulmonis) is rounded, and extends into the root of the neck, 

 reaching from 2.5 to 4 cm. above the level of the sternal end of the first rib. A 

 sulcus produced by the subclavian artery as it curves in front of the pleura runs 

 upward and lateralward immediately below the apex. 



The base (basis pulmonis) is broad, concave, and rests upon the convex surface 

 of the diaphragm, which separates the right lung from the right lobe of the liver, 

 and the left lung from the left lobe of the liver, the stomach, and the spleen. Since 

 the diaphragm extends higher on the right than on the left side, the concavity 

 on the base of the right lung is deeper than that on the left. Laterally and behind, 

 the base is bounded by a thin, sharp margin which projects for some distance 

 into the phrenicocostal sinus of the pleura, between the lower ribs and the costal ( 

 attachment of the diaphragm. The base of the lung descends during inspiration 

 and ascends during expiration. 



ENTRANCE OF 



VENA AZVGOS 



BRANCH OF PUL- 

 MONARY ARTERY 



FIG. 971. Pulmonary vessels, seen in a dorsal view of the heart and lungs. The lungs have been pulled away 

 from the median line, and a part of the right lung has been cut away to display the air-ducts and bloodvessels. 

 (Testut.) 



Surfaces. The costal surface (fades costaiis; external or thoracic surface) is 

 smooth, convex, of considerable extent, and corresponds to the form of the cavity 

 of the chest, being deeper behind than in front. It is in contact with the costal 

 pleura, and presents, in specimens which have been hardened in situ, slight grooves 

 corresponding with the overlying ribs. 



