Abstract
1. When the linearly slowly rising current was applied to the lateral-line endorgan of a Japanese eel (Anguilla japonica), the repetitive responses were obtained from an isolated single lateral-line nerve fiber.
2. In order to examine precisely the relation between the nerve discharges and the stimulating current, a simultaneous recording of these two were made. For this purpose special vacuum tube circuits were designed.
3. The discharge pattern of each nerve fiber encountered differed according to the fiber size.
4. For thin fibers, most of which showed pronounced spontaneous discharges, spike frequencies increased fluctuatingly with the current-increase and they were related to the slopes of rising currents. The increase of the spike frequency, in general, seems to be related directly to the slope, though there was only an irregular relation at a very low voltage.
5. In the cases of thick fibers which show generally no spontaneous discharges, the discharge pattern was of a markedly different kind from that of the thin fiber. Each of these has a certain fixed threshold-voltage to fire, no matter how the gradients of the stimulating currents are. As a matter of fact the discharge frequencies are related not only with the stimulating voltage itself but also with the gradient, namely its change, and such a relation becomes more regular, when the voltage gradient becomes larger. Moreover, this relation between the spike frequency and the voltage in a logarithmic scale is almost linear and the slope of this regression line seems to be concerned in the current gradient, too.
6. The possible maximum frequency to be reached is different for each fiber, the thick fiber having a much higher one, over a hundred, than the thin fiber.
7. For plateau frequencies the thin fiber show a slow adaptation and the discharges continues long, decreasing fluctuatingly, while the thick fiber adapts abruptly. There is always more or less a silent period at the beginning of the plateau phase. At the small slope of the S. C. the mean spike frequencies for the first 1 don't show, a marked difference according to the plateau voltage but when the slope becomes large, they are related linearly with the end-voltage in a semilog. scale. The linear relation in the case of D. C. stimulation may be thought as its limiting case.
8. The place stimulated by a slowly rising current is not exactly known, but the author believes that it may be the nonmyelinated part of the terminal arborisation of the nerve fiber.
9. Histological studies of the nerve endings at the endorgan were performed. It was ascertained that the thick fiber with a myelinated sheath could be traced to the neighbourhood of the sensory cells at the central parts of the receptor, and the terminal nonmyelinated part branched like a tuft and thronged around the sensory cell, while thin fibers lost their sheaths far from the sensory cell and innervated those of the peripheral parts of the endorgan, forming a knob at its extreme end.
10. The authors believe that the validity of the hypothesis previously stated have been ascertained experimentally more.
