THE POSITIVE RESPONSE 189 



and the latter 12 seconds, after the application of the 

 stimulus. 



From these experiments it is seen that while under feeble 

 stimulus we obtain only the positive response, on increasing 

 the intensity of stimulus the negative or excitatory response 

 makes its appearance in succession to the positive. Another 

 noteworthy fact is that while an increasing intensity of 

 stimulus enhances in a marked manner the velocity of 

 transmission of the negative or excitatory impulse, it has 



Fig. 103. — Effect of diminishing the distance of point of application of 

 stimulus. Stimulus applied at a distance of 20 mm. gives rise only to 

 positive response (lower record) . Reduction of distance to half gives 

 rise to positive followed by negative response (upper record). Vibra- 

 tion frequency five times in a second. 



little or no effect on the velocity of the positive impulse. 

 Thus in the first experiment of the series, while the trans- 

 mission-period of the negative impulse was shortened 

 from 0/4 seconds to 4*6 seconds by the stimulus increasing 

 from 5 to 8 units, the transmission period of the positive 

 impulse remained unchanged at # 6 second. 



2. Positive response is more easily obtained under a feeble 

 stimulus applied at a distance. — For the demonstration of 

 this, a feeble stimulus is applied on the stem of Mimosa 

 at a distance of 20 mm. from the responding pulvinus. The 

 response is only positive, occurring 1 second after the 



