212 THE POCKET ANATOMY 



The right bronchus, about i inch long, is shorter, more 

 vertical in direction, and of larger calibre than the left. 

 It passes from the trachea downwards and to the right on a 

 level with the 5th dorsal vertebra to the root of the corre- 

 sponding lung, lying at first above and then behind the right 

 pulmonary artery. The superior vena cava and right phrenic 

 nerve lie in front, and the venaazygos major arches forwards 

 above it. 



The left bronchus is nearly 2 inches long, and passes down- 

 wards and forwards under the arch of the aorta to the root of 

 the left lung, joining it at the level of the upper border of 6th 

 dorsal vertebra. Behind it are the oesophagus, thoracic duct, 

 and descending aorta. It lies at first behind, and then below, 

 the left pulmonary artery. 



THE LUNGS AND THE PLEURAE. 



The lungs, two in number, occupy the whole of the thorax 

 except the mediastina (vide pp. 201 and 202), which separate 

 them from each other. They are conical in shape, and are 

 covered with pleura. Each lung is free except at the median 

 part or root, where it is attached to the bloodvessels and 

 bronchi. 



The pleurae are two serous sacs enclosing and investing the 

 lungs. Each pleura consists of a visceral and parietal layer. 

 The visceral portion covers the lung, and the parietal layer lines 

 the inner surface of the chest walls, the upper surface of the 

 diaphragm, and the sides of the pericardium. The visceral 

 layer of each pleura becomes continuous with the parietal 

 layer in front and behind the root of the lung ; and below 

 the root a fold, the ligamentum latum pulmonis, extends down- 

 wards along the inner surface of the lung to the diaphragm. 

 The mediastina are formed by the visceral layers of each side 

 approaching one another towards the median line. 



The limits of the parietal pleurae are as follows: each 

 extends upwards into the neck, forming a dome-like process 

 over the apex of the lung about 2 inches above the anterior 

 end of the first rib ; from this each pleura passes down- 

 wards and forwards to the posterior aspect of the sterno- 

 clavicular joint and meets its fellow in the mid-line at the 

 manubrio-gladiolar articulation ; they pass down together to 

 level of 4th costal cartilages, where right pleura passes verti- 

 cally to level of yth right costal cartilage in mid-line ; then 

 outwards, crossing gth rib in mid-axillary line ; then down- 

 wards and backwards along nth rib to reach spine at neck of 



