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Scientific Proceedings (129) 



fatigue. It appeared at first that stimulation every third second 

 was the critical "interval" but later experience showed that this 

 only holds good for winter frogs. With fresh spring and sum- 

 mer frogs fatigue was avoided in good experiments with stimuli 

 every second second, sometimes even every second. Even when 

 fatigue occurred, if a pause of about twenty minutes was given 

 in a second series of the same stimuli, fatigue did not result. 

 That the observed difference was due primarily to temperature 

 was shown experimentally by placing the frog in a box in which 

 temperature variations ranging between 15 and 35 degrees were 

 obtained. The state of the summer and winter frog could be 

 reproduced in one and the same animal. 



Cutting the posterior roots caused fatigue to be delayed on 

 the operated side. Microscopic examinations showed no altera- 

 tions. Acetylcholin produced the same delay as cutting the 

 posterior roots. An explanation is given, based on the similar- 

 ity to paralytic secretion after cutting parasympathetic nerves. 



Investigations on the action-current of muscles under the new 

 experimental conditions are being carried out with the help of 

 the highly sensitive American-Swiss-Einthoven-Fahr-Stoppani 

 String Galvanometer. 



The most recent investigations of the biochemical behavior 

 of the muscles working under the new conditions have shown 

 that formation of lactic acid is about ten times less than with 

 the older methods of studying fatigue. 



