The effect of frequency of stimulation on the heat production of frog's nerve

Abstract

The effect of frequency of stimulation on the heat production of nerve has been discovered already in several places, ( a ) by General, Hill, and Zotterman (1927), ( b ) by Hill (1932), both for frog's medullated nerve, and ( c ) by Bersina and Feng (1932) for Crab's non-medullated nerve. The matter is not so simple as has appeared hitherto: the heat per second, or per impulse, depends not only on the frequency but also on the duration of the stimulus. Referring, for example, to fig. 4 in the preceding paper, it is evident that the relation there shown between the rate of heat production during steady stimulation and the number of shocks per second is quite different from that given last year (Hill, 1932, fig. 5, p. 127) for a short stimulus. In the former, half the maximum rate is reached at 26 shocks/sec., in the latter at 80 shocks/sec.; the frequency scales, therefore, are in the ratio of about 1 to 3. Fig. 1 shows the results of an experiment in which the effect of frequency on the heat per impulse was determined ( a ) for a 16-sec. stimulus and ( b ) for continual stimulation until a steady state was reached. In order to keep the figure within responsible dimensions the frequency is given on a logarithmic scale. In ( a ) the heat per impulse has fallen to one-half at a frequency of 140/sec., in ( b ) at a frequency scales again are in the ratio of about 1 to 3. In respect at least of those properties which results in heat production the time scale of nerve is diminished about three times by steady stimulation.