94 Tait 



lation of the nerve under such conditions causes full and complete tetanus 

 of the muscle. Furthermore, had peripheral stimulation been used here, 

 the conductivity of the aiFected portion of nerve would thereafter have 

 been abolished and the experiment temporarily stopped. The fatigue is 

 in the nerve and in it alone. 



From the improvement in the muscle response after each short rest 

 from stimulation it is evident that the fatigue in each case is short-lived. 

 This corresponds to the fatigue already demonstrated by Frohlich (10) in 

 anaesthetised nerve. Although in the present instance the nerve had been 

 in cold rigor subsequent to the actual freezing process, still similar curves 

 are often obtained during the stage of recovery that follows directly upon 

 freezing and thawing. 



(b) More or Less Lasting Fatigue. 



The tracings seen in the next two figures (figs. 4 and 5) are more interest- 

 ing. They are again from a preparation of which the nerve was frozen, 

 the process of freezing having been accompanied in the case by more or less 

 prolonged tetanus and much subsequent twitching of the muscle. On 

 thawing conductivity remained absent for at least twenty minutes. The 

 nerve was put away to rest in Ringer's solution, and its conductivity 

 examined two and a half hours later at room temperature. 



Rhythmical stimulation (rate 144 per second) of the proximal end of the 

 nerve first produced the effect seen in fig. 4, tracing 4, viz. " fatigue tetani," 

 Almost immediately afterwards the muscle responses were of the form seen 

 in tracing 5, after which peripheral stimulation of the nerve was carried 

 out — tracing 6. The smooth and elevated tetani which follow upon 

 peripheral stimulation show that the muscle is in normal condition and not 

 fatigued. After a rest of about five minutes, stimulation was now applied 

 to the proximal end of the nerve, with the result seen in tracing 7. It can be 

 seen that with each succeeding series of excitations the corresponding muscle 

 responses, which are of the " fatigue tetanus " form throughout, become less 

 and less vigorous, and tend eventually to die away. 



Another rest of about five minutes was given, and series of rhythmical 

 stimulations at a constant intensity of 500 units once more applied to the 

 central end of the nerve, with an exactly similar result to the previous one 

 (see fig. 5, tracing 1), only that this time the muscle responses died away 

 completely in the end. A rest of four minutes was given, and another two 

 tetani inscribed with central stimulation. Seeing that the same process of 

 gradual extinction of the muscle response was evidently going to be 

 repeated, the nerve was then stimulated peripherally so as to make 

 absolutely sure that no fatigue of the muscle had occurred ; the result of 

 this peripheral stimulation, however, is that the nerve now refuses to 

 conduct excitations applied at the central end. As explained in the above- 

 mentioned paper (2), the result of strong peripheral stimulation, when the 

 nerve is already in a fatigued condition due to rhythmical central stimula- 



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