Summary
The fine structure and electrophysiological properties of the cerebrovisceral connective of a fresh-water mussel, Cristaria plicata, were studied. All axons in the connective, whose diameters range from 0.05 to 6.0 μ, are unmyelinated and they are not ensheathed by satellite cells like Schwann cells. The satellite cells are scattered in large numbers among the axons and have extensive arborizations but they do not subdivide the connective into fascicles. Therefore, most of the axons are flanked on all sides by other axons and separated from each other only by a small gap about 100–250 Å wide. The cytoplasm of a satellite cell contains osmiophilic granules and fibrils. Some axons contain small granules which resemble neurosecretion granules.
The action current of the connective showed three elevations. The conduction velocities were 300–400 mm/sec, 60–80 mm/sec and 30–40 mm/sec respectively. There was no evidence indicating the existence of a suprathreshold interaction among the axons.
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The author wishes to appreciate the encouragement and advice of Professor Junnosuke Nakai (Anatomical Department of the University of Tokyo) and Associate Professor Atsushi Ichikawa (Anatomical Department of the University of Tohoku). Sincere thanks are expressed to Professor J. C. Sinclair (Anatomical Department of the University of Texas)for his kindness in correcting the manuscript. Thanks are also due to Dr. Shigehiro Nakajima (Physiological Department of the University of Tokyo) for his collaboration in respect of the electrophysiological aspect of this study.
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Nakajima, Y. Electron microscope observations on the nerve fibers of Cristaria plicata . Zeitschrift für Zellforschung 54, 262–274 (1961). https://doi.org/10.1007/BF00338707
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DOI: https://doi.org/10.1007/BF00338707