THE LUNG 319 



numbers at the periphery of the primary and secondary lobules (Miller, 

 Anat. Rec., 5, 3, 1911). 



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 fibers, and to the walls of the 

 bronchial tubes. Small nerve trunks, with which many minute ganglia 

 are connected, occur in large numbers in the outer fibrous coat of the 

 bronchi. 



From these nerve trunks and ganglia fibrils are distributed to the 

 bronchial mucous membrane, in which they supply the muscularis 

 mucosae, and form a terminal plexus beneath the epithelial coat. These 

 fibers have been traced to the respiratory bronchioles, where they are 

 said to form a delicate plexus within' the lobule in the interalveolar walls 

 (Wolff, Arch. f. Anat., 1902). Sensory fibrils are supplied by the vagus 

 nerve. The vagus contributes to the bronchi and their subdivisions also 

 motor fibers, for the most part probably indirectly through the sym- 

 pathetic ganglia. 



