THE APPLICATION OF QUANTITATIVE STIMULUS 43 



former, the intensity of stimulation was seen to depend on 

 the amplitude of vibration. In the latter, stimulus intensity 

 was determined by that of the thermal variation, which again 

 was regulated by the intensity and duration of the electrical 

 heating-current. It was also seen to be important that the 



FIG. 32. Genesis of Tetanus in Muscle 



Record to left shows incomplete tetanus, with moderate frequency of 

 stimulation. Record to right shows tetanus more complete, with 

 greater frequency of stimulation (Brodie). 



excitation of one contact should be prevented from reaching 

 the other, and this was provided against in two different 

 ways. In the first of these, a physical block was interposed 

 between the two contacts. In the second, the distal contact 

 was made with the non-conducting tissue of a lateral leaf. 



(b) 



FIG. 33. Photographic Record 

 of Genesis of Tetanus in 

 Mechanical Response of 

 Plants (Style of Datura alba} 



FIG. 34. Fusion of Effect or 

 Rapidly Succeeding Stimuli 



(a) in muscle ; (/>) in carrot. 



When these precautions were observed, it was found that 

 uniform stimuli induced uniform response. Stimuli which 

 were singly ineffective, were found on repetition to become 

 effective. A tetanic effect was obtained bv the rapid super- 

 position of stimuli. 



