202 



IRRITABILITY 



the conditions necessary for the genesis of inhibition are realized 

 in the existence of the refractory period, and that I had already 

 produced inhibition by prolonging the refractory period, by 

 oxygen withdrawal, in the strychninized frog. If we take a 

 strychninized frog in which the refractory period has been some- 

 what prolonged by oxygen withdrawal, so that the reaction is 

 simply a short reflex contraction, and rhythmically stimulate the 

 skin, a reaction is only obtained with the first few stimuli, which 



Fig. 45. 



Lower line indicates stimuli. 



reactions rapidly decrease until a stage is reached wherein the 

 succeeding stimuli are completely inoperative. (Figure 45.)^ 

 This inhibition is demonstrated even more clearly by the following 

 experiment. Contractions of the triceps muscle of a strychninized 

 frog are recorded which reflexly follow from stimulation of the 



1 Max Verworn: **Zur Kenntniss der physiologischen Wirkungen des Strychnins.'* 

 Arch. f. Anat. u. Physiol, physiolog. Abth. 1900. The same: "ErmGdung, Erschopfung 

 und Erbolung." Ibidem Suppl. 1900. 



