NERVE SUPPLY 249 



veins and join the azygos veins. Thus, only the walls of the 

 larger bronchial tubes are supplied with bronchial blood, and, ac- 

 cording to Schaffer, a few branches at the root of the lung are also 

 distributed to the adjacent pleura. Many of the bronchioles, the 

 terminal bronchioles, and also the alveolar ducts, pulmonary al- 

 veoli, and the pleura all receive their nutrition from the pulmon- 

 ary arteries. Finally it may be said that there are no anastomoses 

 between the pulmonary arteries and veins except among the capil- 

 laries of the alveolar walls. 



LYMPHATICS. The pulmonary lymphatics form .a plexus in 

 the walls of the bronchi and bronchioles, the smaller vessels being 

 found in the mucous membrane, the larger in the outer fibrous 

 coat. Branches from this plexus frequently anastomose with 

 perivascular lymphatic vessels about the branches of the pulmon- 

 ary artery and veins. A close network of lymphatic vessels is also 

 found in the pleura, its efferent vessels passing into the inter- 

 lobular tissue to join those vessels which accompany the veins. 

 The pulmonary lymphatics are supplied with frequent valves and 

 numerous anastomoses. 



The lymphatic vessels of the bronchi are connected with larger 

 lymphatic vessels of the outer fibrous coat and with the lymphatic 

 nodules in the walls of the larger tubes. Many of the larger ves- 

 sels in the outer fibrous coat of the bronchi, and also those which 

 accompany the pulmonary artery, enter those lymphatic glands 

 which are in relation with the bronchial walls at the root of the 

 lungs. The pleural lymphatic plexus and the vessels accompany- 

 ing the pulmonary veins, after pursuing much of their course 

 through the interlobular connective tissue in company with the 

 pulmonary veins, also open into the bronchial lymphatic glands. 

 Much pigment is conveyed through these vessels and is deposited 

 in (a) the interlobular connective tissue, (b) the fibrous tissue 

 about the pulmonary arteries, and most abundantly in (c) the 

 bronchial lymphatic nodules and glands. 



NERVE SUPPLY. The nerves of the lungs are derived from 

 the anterior and posterior pulmonary plexuses of the sympathetic 

 system. They are distributed to the walls of the blood vessels, 

 where they form a delicate plexus with terminal fibrils among the 

 smooth muscle fibres, and to the walls of the bronchial tubes. 

 Small nerve trunks, with which many minute ganglia are con- 

 nected, occur in large numbers in the outer fibrous coat of the 

 bronchi. 



