204 IRRITABILITY 



consequence there is a strong reduction of irritability and re- 

 action is absent. That is, the centers during application of the 

 frequent current are inhibited. If cessation of stimulation by 

 frequent shocks takes place, stimulation by slowly succeeding 

 individual shocks becomes effective again in a few seconds. This 

 is the simplest example of the process of inhibition and by it I 

 was led to seek in the refractory period the key of the mechan- 

 isms of the process of inhibition. This principle once recognized, 

 further material for the more detailed working out and extension 

 of the theory was gathered from the experiences already gained 

 during the course of the preceding years in the researches on 

 fatigue and the refractory period in the nerve. Here it became 

 apparent that the processes resembling inhibition discovered by 

 Schiff in the nerve preparation and which were studied anew at 

 a later date by Wedenski, F. B. Hofmann and Amaja and in part 

 attributed by Hofmann to fatigue of the nerve endings, by 

 Frohlich to fatigue of the nerve itself, were in principle of the 

 same nature as the central inhibitions themselves. Frohlich,'^ by 

 his analysis of the observations of Richet, Luchsinger, Fick, 

 Biedermann and Piotrowski on inhibition in the claw of the crab, 

 then showed that inhibition can be influenced by the alteration of 

 the intensity of the stimulus as well as its frequency. In a series 

 of experimental researches he could then demonstrate that the 

 widely extended antagonistic inhibitions and other special pro- 

 cesses of inhibitions in the centers could on the basis of the same 

 principle be physiologically explained. Here the supposition was 

 confirmed that the development of a relative refractory period 

 plays a very important role in the inhibition of the nervous cen- 

 ters. Thus, the relations of the processes of inhibition to the 

 refractory period, once established, their entire field, up to then 



1 Fr. W. Frohlich: "Die Analyse der an der Krebsschere auftretenden Hemmun- 

 gen." Zeitschr. f. allgem. Physiologie Bd. VII, 1907. The same: "Der Mechanismus 

 der nervosen Hemmungsvorgange." Medizin. naturwiss. Arch. Bd. I, 1907. The 

 same: "Beitrage zur Analyse der Reflexfunction des Riickenmarks mit besonderer 

 Beriicksichtigung von Tonus, Bahnung und Hemmung." Zeitschr. f. allgem. 

 Physiologie Bd. IX, 1909. The same: "Experimentelle Studien am Nervensystem der 

 Mollusken 12. Summation und scheinbane Bahnung, Tonus, Hemmung und 

 Rhythmus am Nervensystem von Aplysia limacina." Zeitschr. f. allgem. Physiol. Bd. 

 XI, 1910. 



