CHAPTER XXXV 



EFFECT OF DIFFUSE STIMULATION ON AUTONOMOUS 



TORSION 



The effects of different modes of diffuse stimulation on auto- 

 nomous torsion will be specially studied in this chapter. 

 I begin with the effect of electric stimulation. 



Response to Electric Stimulation 



The great advantage of the electric mode of stimulation 

 is that (i) it causes no mechanical disturbance in the record, 

 and that (2) the intensity can be increased from minimal 

 to maximal by the gradual approach of the secondary to 

 the primary coil. The two electrodes from the secondary 

 coil are applied one above and the other lower down on the 

 stem, so that the induction current passes along the length 

 of the organ. Since the effect of stimulus is additive, the 

 effectiveness of stimulation depends on the product of 

 intensity and duration. A minimal stimulus may thus 

 become maximal by prolonging the duration of application. 



As in other responding organs, a certain period elapses 

 between the reception of stimulus, and the response, which 

 continues for a time even after the cessation of stimulation. 



Effect of Strong Stimulation 



Experiment 214. — I will first describe the effect of 

 electric stimulation applied for 2 minutes on a vigorous 

 specimen of Thunbergia. The normal rate was 28 mm. per 

 minute. In response to stimulation the normal rate in the 

 positive direction was diminished, culminating in reversal 

 of direction to negative 3 minutes after the application 



