MULTIPLE RESPONSE 



285 



uniform stimuli exhibited periodic fluctuations (p. 106). We 

 may thus have an alternate, periodic, or cyclic fluctuation of 

 excitability exhibited in the responses. In the first of these, 

 the responses are alternately large and small. In the last, 

 we may have either an ascending or descending series, which 

 is periodically repeated. 



Cyclic variation in multiple response. — In multiple 

 responses also we find all these types. And if the seat of 

 origin of the multiple excita- 

 tion be at a distance from the 

 responding leaflet, we have 

 in this fact an added element 

 of variation. For we have 

 now to consider, not simply 

 the periodic variations of ex- 

 citability of the motile organ, 

 but also those of the excita- 

 bility of the intervening tissue, 

 causing periodic changes of 

 conductivity. Hence, in re- 

 cords obtained of multiple 



responses, where the seat of excitation is at a distance, we 

 have a complex combination of variations of amplitude and 

 of period in the pulsations. 



Confining our attention to the period alone, we find that 

 multiple responses may be classified under three headings : 



Fig. 117. Multiple Response in 

 Biophytum 



The rhythm, at first slow, becomes 

 quicker. 



Fig. 118. Multiple Response in Biophytum 

 Quick rhythm becoming slow. 



those in which the successive periods are fairly uniform 

 (fig. 116); those in which the pulsations are at first slow and 

 later become quicker (fig. 117) ; and those which begin with 



