. Comparative physiology. Physiology, Comparative; Physiology, Comparative. 136 COMPARATIVE PHYSIOLOGY the first, if adequate to set up a nervous impulse, for a measur- able interval after the refractory phase leaves the point of excitation in a more excitable state, so that with an appropriate period intervening between the two stimuli a second one of subminimal intensity may become an effective agent of excitation. The time-relations in the case of the frog's sciatic gastrocnemius preparation are represented by Adrian and Keith Lucas, as in Fig. 34. Their possible bearing on the phenomena of
. Comparative physiology. Physiology, Comparative; Physiology, Comparative. 136 COMPARATIVE PHYSIOLOGY the first, if adequate to set up a nervous impulse, for a measur- able interval after the refractory phase leaves the point of excitation in a more excitable state, so that with an appropriate period intervening between the two stimuli a second one of subminimal intensity may become an effective agent of excitation. The time-relations in the case of the frog's sciatic gastrocnemius preparation are represented by Adrian and Keith Lucas, as in Fig. 34. Their possible bearing on the phenomena of inhibition and summation in the central nervous system will be dealt with later. We must first consider the. •01 -02 Time since previous stimulus {seconds) Fig. 34.—Excitability to second stimulus in the sciatic gastrocnemius preparation of the frog (Adrian and Keith Lucas). light they throw on the nature of the local change which precedes the propagated disturbance in nerve. To account for both the refractory period and the supernormal phase we may picture this change as a phenomenon of disintegration ; if excitation involves dissolution of some constituent in the neighbourhood of the electrode, we should expect no further stimulus to have any effect so long as the latter state persists ; and if the disintegrative process is reversible, it is possible to conceive why this period should be followed by one in which, restoration being incomplete, a less potent stimulus is required to reverse the process. Further light is shed on the problem by taking into account. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hogben, Lancelot Thomas, 1895-. New York, The Macmillan Company
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