in fig. 87 show that there is a complete recovery of the tissue one minute after the application of the stimulus.
Fig. 87. Appearance of fatigue in plant under shortened period of rest.
The molecular condition is exactly the same at the end of the recovery as at the beginning of stimulation; the second and succeeding response-curves therefore are exactly similar to the first, provided sufficient interval in each case has been allowed for complete recovery.
The rhythm was next changed and stimuli of the same intensity as before applied at intervals of half a minute, instead of one. It will he noticed that these responses in the second part appear much feebler than those in the first set, in spite of the equality of stimulus. The original rhythm of one minute was now restored and the succeeding curves at once show restoration of the original amplitude of response.
Increased Response under increasing Stimulus
I will now show that the electric response is not merely a qualitative phenomenon, but that increased intensity of stimulus always gives rise to a definite increase in the amplitude of response.
In order to obtain the simplest type of effects, not complicated by secondary phenomena, it is necessary
