Abstract
All analysis of the vagus nerves of the cat and turtle (Hein-becker 1 ) demonstrated 3 distinguishable potential complexes. The first had physiological properties characteristic of somatic nerve fibers, the other 2 had properties of a much slower order, properties which our subsequent investigations have associated with autonomic motor functions. A correlation between potential form and nerve fiber type as revealed in osmicated cross sections of nerve indicates that the first potential complex is derived from larger myelinated fibers, the second from small thinly myelinated fibers and the third from non-myelinated fibers.
Experiments have been performed on the cat in which stimulating and recording electrodes were placed on the central portion of one cervical vagus nerve in an animal in which both nerves were cut. The potential record of the nerve was observed coincidentally with the physiological effects in the animal resulting from electrical stimulation. The afferent fibers whose activity is responsible for respiratory and vascular reflex effects are found to fall in the group giving rise to the first potential complex. No further effects are elicited by stimuli strong enough to excite the fibers giving rise to the second and third potential complexes.
The vagus nerve above the nodose ganglion was sectioned in cats and after sufficient time for degeneration the vagus nerve trunk in the neck was studied functionally. In such preparations adequate stimuli failed to cause slowing of the heart rate, but normal results from the fibers responsible for certain motor effects in the lungs and duodenum were still obtained.
Section of vagus roots at their exit from the brain stem after sufficient time for degeneration had a similar effect, indicating that the fibers responsible for slowing of the heart rate have their cells of origin within the central nervous system.
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