94 



COMPARATIVE ELECTRO-PHYSIOLOGY 



seen in fig. 63, where the first set of these responses, A, is for 

 an intensity of mechanical stimulation of 45 vibration, and 

 the second set, B, of augmented amplitude, for an intensity 

 of 90 vibration. On reverting, in c, to the first stimulus- 

 intensity of 45, the re- 

 sponses are seen to undergo 

 a great diminution, as com- 

 pared with the first set, A. 

 This change is due to the 

 over-strain of the previous 

 excessive stimulation. But 

 we should expect that the 

 effect of such over-strain 

 would disappear with time, 

 and the responses regain 

 their former height, after a 

 FIG. 62. Photographic Record showing period of rest. In order to 



in Tin W 



Fatigue in Tin Wire which had been 

 continuously stimulated for several 

 Days 



verify this, therefore, I re- 

 newed stimulation (at the 

 intensity of 45) fifteen 



minutes after C. It will be seen from the record D how far 



fatigue had been removed in this interval. 



45 



45 



FIG. 63. Effect of Over-strain in producing Fatigue 



Successive stimuli applied at intervals of one minute. The intensity ot 

 stimulus in c is the same as that of A, but response is feebler owing to 

 previous over-stimulation. Fatigue is to a great extent removed after 

 fifteen minutes' rest, and the responses in D are stronger than those in 

 c. The vertical line between arrows represents -05 volt. (Turnip 

 leaf-stalk.) 



One peculiarity that will be noticed in these curves is 

 that, owing to the presence of comparatively little strain, the 

 first response of each set is relatively large. The succeeding 





