VARIOUS TYPES OF RESPONSE 



79 



was then effective in evoking a feeble response. The most 

 striking fact, however, is that on the completion of recovery 

 the specimen actually exhibited a growing contraction as 

 an after-effect of stimulus. Thus, while at the beginning 

 a growing condition of a-tonicity gave rise to increasing 

 relaxation, afterwards in consequence of stimulation this 

 state of things became reversed, and we have a growing 

 condition of tonic contraction appearing as the after-effect 

 of stimulus. That the tonic condition in fact became 

 improved is shown by the large 

 response evoked as the immediate 

 effect of the usual stimulation. i 



This after-effect of a single 

 stimulus in inducing a second 

 contraction is significant as show- 

 ing the possibility of holding inci- 

 dent stimulus latent for a time, to 

 find expression later. It heralds 

 the phenomenon of Multiple Re- 

 sponse, which we shall consider in 

 a subsequent chapter. 



The curious phenomenon of 

 alternation sometimes observed in 

 a highly excitable specimen has 

 already been noticed (fig. 36). 

 The characteristic peculiarity ob- 

 served there was a large response 

 followed . by a small one, such 

 alternation continuing for a time, 

 successive responses, however, vanished after a time. With 

 plants in a sub-tonic condition the phenomenon of alterna- 

 tion is also found occasionally. The characteristics here 

 exhibited (fig. 40) are in sharp contrast to those seen in 

 fig. 36. Here the first response is small, and the second 



Fig. 39. — Record showing 

 the effect of stimulus 

 modifying tonicity, and 

 producing staircase 

 effect. 



The difference between 



^ When the specimen is extremely sub-tonic the sign of response 

 may even be reversed into abnormal erectile movement. After a period 

 of stimulation, however, the response is converted into normal. 



