1198 THE ORGANS OF VOICE AND RESPIRATION 



chial artery usually arises from the first right aortic intercostal, but sometimes from the superior 

 left bronchial artery, or from the aorta. In the root of the lung they are posterior to the bron- 

 chus, they accompany the bronchial tubes, supply the bronchial tubes and surrounding inter- 

 lobular tissue, and give branches to the walls of the larger pulmonary vessels, the oesophagus, 

 pericardium, and bronchial lymph nodes. Those supplying the bronchial tubes form a capil- 

 lary plexus in the muscular coat, from which branches are given off to form a second plexus in 

 the mucous coat. This plexus anastomoses with branches of the pulmonary artery, and empties 

 into the pulmonary vein. Others are distributed in the interlobular areolar tissue, and terminate 

 partly in the deep, partly in the superficial, bronchial veins.. Lastly, some ramify upon the 

 surface of the lung beneath the pleura, where they form a capillary network. There may be 

 but one bronchial artery; there may be three or four. 



The bronchial veins are not found in the walls of the very small bronchi. The small bronchial 

 veins run along by the front and back of the medium sized and larger tubes, and form two trunks 

 at the root of each lung. These vessels terminate on the right side in the vena azygos major, 

 and on the left side in the superior intercostal or left upper azygos vein. Tracheal and posterior 

 mediastinal veins open into the bronchial veins. The venous blood from the smaller tubes 

 passes to the pulmonary veins. 



INTERLOBULAR 

 BRONCHUS 



ALVEOL 

 DUCT 



BRONCHIOLE 



RESPIRATORY 

 BRONCHIOLE 



FIG. 911. A pulmonary lobule. (Poirier FIG. 912. The terminal bronchial tubes. The respiratory 



and Charpy.) bronchiole and alveoli. (Poirier and Charpy.) 



The lymphatics begin in networks about the lobules and form networks about the bronchi 

 and beneath the bronchial mucous membrane. The superficial collecting trunks arise about 

 the lobules and beneath the pleura. According to Sappey, the superficial trunks from the upper 

 lobe begin on the costal surface; one set passes around the anterior border, another set around 

 the posterior border, and a third into the incisura interlobaris. The same observer says that 

 the superficial trunks from the middle lobe unite with the trunks from the upper and lower lobes; 

 and the superficial trunks from the lower lobe, like those of the upper lobe, are in three sets. 

 One set passes around the posterior margin, one around the anterior margin, and one into the 

 interlobar fissure. All of the superficial trunks convey lymph to the nodes of the hilum. Some 

 of the deep collecting trunks begin by the side of the small bronchi; others course along by the 

 pulmonary veins or pulmonary arteries. All of them pass to the nodes of the hilum. The 

 nodes of the hilum are in communication with the peritracheobronchial nodes. 



Nerves. The lungs are supplied from the anterior and posterior pulmonary plexuses, formed 

 chiefly by branches from the sympathetic and vagus. The filaments from these plexuses accom- 

 pany the bronchial tubes, and are lost upon them. Small ganglia are found upon these nerves. 



Surface Form. The apex of the lung is situated in the neck, behind the interval between the 

 two heads of origin of the Sternomastoid muscle. The height to which it rises above the clavicle 

 varies very considerably, but is generally about one inch. It may, however, extend as much as 

 an inch and a half or an inch and three-quarters, or, on the other hand, it may scarcely project 

 above the level of this bone. In order to mark out the anterior margin of the lung, a line is 

 to be drawn from the apex point, one inch above the level of the clavicle, and rather nearer the 



