334 



Dr. K. Sassa. Observations on Reflex 



height' and course. A definite relationship exists between the intensity at 



different frequency-rates and the 

 extent of the reflex reaction obtained. 



Two methods were adopted of 

 examining this point. In both, 

 several series of reflex responses 

 were recorded. In the first, the 

 frequency was fixed for each series, 

 and the intensity varied within it. 

 In the second, the intensity was 

 fixed for each series, and the rate of 

 stimulation varied. 



(1) Frequence/ Fixed, Intensity 

 Varied. — With low rates (under 

 thirty per second), the reflex re- 

 action increases with the intensity 

 of stimulation, at first quickly and 

 then more slowly. Sometimes an 

 intensity is reached, after which no 

 further increase of contraction can 

 be elicited by further increase in 

 the intensity of stimulation. At 

 higher frequency-rates (more than 

 sixty per second), the reflex con- 

 traction increases rapidly with the 

 strength of stimulation to a maxi- 

 mum, and from this point decreases 

 with each increment of stimulation. 

 An optimal intensity of stimulation 

 therefore exists at this frequency- 

 rate. Between these two extremes 

 there is a critical value of the 

 frequency-rate, at which the height 

 of contraction remains almost con- 

 stant after quickly attaining its 

 maximum, in spite of steady increase 

 of intensity of stimulation. In other 

 words, the strength of the reflex 

 reaction under this optimal rate of 

 frequency is independent, within wide limits, of the strength of the stimulation 



