14 CHANGES OF EXCITABILITY IN NERVES 



of the same nature as those which occurred at the anode at 

 closure.' 



In a provisional communication on his investigation, which, so 

 far as I know, was not published, Griinhagen ] very briefly made 

 known the results he had obtained relative to the duration of 

 the changes in excitability produced by a constant current. In 

 this research he employed tetanus and its changes on closing and 

 opening the current. He applied the test-stimulus between the 

 polarising current and the muscle, and found that the tetanus 

 in anelectrotonus fell off and in katelectrotonus increased, in such 

 a way that in the first case the changes of excitability were longer 

 in fully pronouncing themselves than in the latter. On the other 

 hand, he could make out no change of excitability at the negative 

 pole consequent on opening. An increase of excitability at the 

 anode during the first moments after opening of the current, 

 such as Wundt had observed, Griinhagen could not establish. 

 Finally, he found an immeasurably short duration of increase in 

 excitability at the kathode after interruption of the current. On 

 these disagreements with Wundt's result we can lay no stress 

 to the disadvantage of the latter, since the author has neither 

 here nor since given a full statement of his experiments. The 

 chief fact is that Griinhagen has confirmed Pfliiger's laws in the 

 most essential points. 



The researches then which have been instituted since the ap- 

 pearance of Pfliiger's work, to determine the changes of excitability 

 in a fresh nerve elicited by a constant current, have, in essentials, 

 confirmed Pfliiger's results, and have, further, supplemented them 

 with new investigations on the changes of excitability occurring 

 directly after closure and opening of the current (Wundt, Griin- 

 hagen). The theoretical difference between Pfliiger and Hermann 

 is however still undecided ; and the experiments instituted by the 

 latter on the inhibitory influence of the negative pole with 

 powerful currents constitute for the present very weighty ob- 

 jections to Pfliiger's theoretical view. 



Under such circumstances, and as hitherto no investigation of 

 the changes of excitability has been instituted with purely me- 

 chanical stimuli, I considered that there were sufficient reasons 

 for taking up the enquiry once more from this point of departure, 

 the more so that the mechanical method of stimulation, with 



J Griinhagen, Archiv ftir die geeammte Physiologic, iv, 1871, pp. 547-55- 



