Nerve terminations in the lung of the rabbit

The innervation of the mammalian lung appears to be little understood by either anatomists or physiologists. The average text-book description states that the lungs receive their nerve supply from the sympathetic system by way of the pulmonary plexuses, and that the vagus nerve also contributes fibers. Usually references, more or less vague, are made to motor terminations in the bronchial musculature and in that of the pulmonary artery, and also to sensory terminations in the parenchyma of the lung. Physiologists have evidence for the presence of both sensory and motor fibers in the bronchi and their branches, but concerning the vasomotor control of the pulmonary circulation they have obtained discordant results. It was with the hope of throwing further light on this subject that the present investigation was undertaken at the suggestion of Dr. W. S. Miller, to whom the writer is greatly indebted for assistance with difficult points of the anatomy of the lung. The general problem undertaken has to do with the distribution and arrangement, as well as the source, of the nerve fibers which enter the lung, in addition to the types of nerve terminations and the position of the latter within the organ. A description of the fibers, their origin and the relation of the intrapulmonary ganglia is reserved for a subsequent report, and these points will be touched upon at present only to the extent necessary to make clear the relations of the various sensory and motor terminations which are described.