CHAPTER X 



INFLUENCE OF INTENSITY OF STIMULUS, FATIGUE, AND 

 TEMPERATURE ON THE LATENT PERIOD 



Diffuse stimulation under alternating shock — Effect of intensity of 

 stimulus on Latent Period — Influence of optimum condition — Effect 

 of fatigue — Effect of temperature, 



I WILL now describe different experiments carried out 

 for the purpose of observing the effect of varying external 

 conditions — such as the intensity of stimulus, fatigue, and 

 temperature — on the latent period. The mode of pro- 

 cedure adopted was first to take a record giving the latent 

 period under standard conditions, and then to make further 

 records under conditions similar in all respects to the first, 

 except in regard to the one special factor whose influence 

 was to be determined. 



As some of the experiments in question necessitated 

 a long period of observation, lasting sometimes over an 

 hour, it became necessary to eliminate one source of possible 

 uncertainty — namely, the effect of electrolytic contact on 

 the pulvinus. It has been shown that there is no variation 

 of excitability induced in the pulvinus where the contact 

 is made with glycerin. It would, however, be preferable 

 to effect direct stimulation without placing either of the 

 electrodes on the pulvinus. In connection with this it was 

 found that if one of the two electrodes were placed on the 

 petiole slightly to the right of the pulvinus, and the other 

 on the stem immediately below it, and a few rapidly alter- 

 nating shocks passed through, excitation was simultaneous 

 throughout the interposed tract. 



This may be demonstrated in a striking manner by 



