THE MAMMALIAN lung is innervated abundantly by autonomic nerves that enter the hilus for distribution in the peribronchiolar tissues into the terminal segments of the air passages.1-3 Many of these hilar nerves have thick and thin myelinated axons, clusters of ganglion cells and unmyelinated fibers. These and other characteristics identify them as vagal. Hilar nerves, less frequent and more fibrillar, have thin and a few thick myelinated axons, unmyelinated fibers and by their structure are recognized as sympathetic. The mammalian lungs have many afferent receptors.4-7 These terminals of myelinated axons, mainly but not exclusively vagal, are recorded as (1) fiber ramifications among the lining epithelial cells of the bronchioles, (2) encapsulated or unencapsulated sessile and pedunculated receptors in the subepithelial tissues of the bronchioles, the alveolar ducts and the alveolar sacs, (3) curved segments of thick sinuous fibers with fibrils and their branches in the walls of