Abstract
In the toad carotid nerve the fiber components and their physiological role were studied. In addition the fiber composition was examined by light and electron microscopy. The carotid nerve consisted of 4 groups of fibers originated from the vagus group and the sympathetic: 1) slowly conducted fibers taking origin in V1-root, 2) rapidly conducted fibers from V2-root, 3) slowly conducted fibers derived from V2-root, and 4) sympathetic fibers. Fibers of V1-root origin were chemosensory. They conveyed impulses at the rate of about 0.3m/sec, suggesting that they were non-medullated. Rapidly conducted fibers derived from V2-root transferred baro-sensory impulses at the rate between 1m/see and 7m/sec, suggesting that they were medullated. They were rapid adapting and some of them made synapses in the jugular ganglion. In respect to slow V2-root fibers it was supposed that they were non-medullated and efferent nerve fibers to the chemoreceptor cell. Sympathetic fibers were derived from SIII-SV, mainly from SIV On their function it was discussed that they may be vasoconstrictors to the vasculature of the carotid labyrinth in the major part and partly inhibitory fibers to the chemoreceptor cell. On the anatomical observation the carotid nerve consisted of many non-medullated fibers and a small number of medullated fibers in diameter of 2-4μ.
