ORGANS OF VOICE AND RESPIRATION 213 



rath rib. Behind, it passes upwards on right side of bodies of 

 vertebras to apex. At level of 4th costal cartilage the left pleura 

 arches outwards, leaving uncovered part of anterior surface 

 of pericardium, and lying about f inch from the margin of 

 sternum, to reach yth left costal cartilage, below which it 

 follows same line as on right, but is placed at a slightly lower 

 level. 



THE LUNGS. 



Each lung is cone-shaped, with the base downwards. 



The apex projects upwards into the root of the neck behind 

 the clavicle and anterior scalene muscle. Above the first 

 rib, the first part of the subclavian artery lies in front, being 

 separated from it by the pleura. 



The base is concave, resting upon the diaphragm, and 

 following the attachment of the midriff is placed lower ex- 

 ternally and posteriorly than anteriorly. 



The outer surface is convex, and corresponds to the chest 

 wall. 



The inner surface is concave, corresponding in part to the 

 convex outer surface of the pericardium. It presents about 

 its middle, and towards the posterior part, a slit, the hilum 

 pulmonis, where the bronchi and vessels pass in to form the 

 root. 



The anterior margin is thin, and overlaps the pericardium, 

 and presents on the left side a notch for the apex of the 

 heart. 



The posterior margin is rounded, and occupies the groove by 

 the side of the vertebrae. 



Fissures and Lobes. The left lung is smaller and narrower 

 than the right, and is divided into an upper and lower lobe 

 by a fissure, which passes upwards and backwards from the 

 anterior border nearly to the root. The right lung is larger 

 and shorter than the left, and is divided into three lobes, 

 upper, middle, and lower, by two fissures. One fissure passes 

 obliquely from the outer surface upwards and inwards nearly 

 to the root, and the second passes horizontally from the 

 middle of the first, forwards to the anterior margin, cutting 

 off a middle triangular lobe. 



Each root consists of the corresponding bronchus, a branch 

 of the pulmonary artery, two pulmonary veins, nutritive 

 bronchial vessels, anterior and posterior pulmonary plexuses, 

 lymphatic vessels and glands, all held together by areolar 

 tissue, and covered by the pleura. 



