INTERFERENCE OF EXCITATIONS 203 



central end of the cut sciatic nerve. Oxygen is withdrawn in the 

 manner already referred to. At the proper stage of oxygen 

 deficiency, rhythmic induction shocks applied to the central end 

 of the nerve, the interval between the individual stimuli of which 

 being longer than the duration of the refractory period, elicit 

 reflex contractions of the muscles of the posterior extremity on 

 the opposite side following each individual stimulus. If, how- 

 ever, in the same stage the central end of the nerve is stimulated 

 with induction shocks at intervals briefer than the duration of 

 the refractory period, a contraction is only observed during the 



Fig. 46. 



Reflex inhibition in the strychninized frog. Lower line indicates seconds, upper line stimuli. 

 When stimulation with single shocks at longer intervals is applied, each single stimu- 

 lus is effective. When faradic stimulation is used, only the first stimulus is operative, 

 and during the further continuance of stimulation inhibition takes place in the spinal 

 cord. 



very beginning, being brought about by the first stimulus, whereas 

 the subsequent stimuli are ineffective, the muscles remaining at 

 rest during their entire application. (Figure 46.) Tiedemann 1 

 at a later date continued these observations and analyzed them 

 more in detail. In all these experiments, therefore, there is an 

 interference of the frequent stimulus, because each succeeding 

 stimulus occurs in the refractory period of the proceeding. In 



1 Tiedemann: "Untersuchungen iiber das absolute Refractarstadium und die 

 Hemmungsvorgange im Riickenmark des Strychninfrosches." Zeitschr. f. allgem. 

 Physiologic Bd. X, 1910. 



