78 RESPONSE IN THE LIVING AND NON-LIVING 



be desired as to the effect of the reagent, we can 

 obtain it by alternate stimulation of the A and B ends. 

 Both ends will then show the given change. I give 

 below a record of responses given by two ends of leaf- 

 stalk of turnip, stimulated alternately in the manner 

 described. The stalk used was slightly conical, and 

 owing to this difference between the A and B ends the 

 responses given by one end were slightly different from 

 those given by the other, though the stimuli were 



Before After 



FIG. 47. ABOLITION OF BESPONSE AT BOTH A AND B ENDS BY THE ACTION 



OF NaOH 



Stimuli of 30 vibration were applied at intervals of one minute to A and B 

 alternately, Kesponse was completely abolished twenty-four minutes after 

 application of NaOH. 



equal. A few drops of 10 per cent, solution of NaOH 

 was applied to both the ends. It will be seen how 

 quickly this reagent abolished the response of both 

 ends (fig. 47). 



Effect of dose. It is sometimes found that while a 

 reagent acts as a poison when given in large quantities, 

 it may act as a stimulant in small doses. Of the two 

 following records fig. 48 shows the slight stimulating 



