PLANT RESPONSE 39 



in fig. 20, a. It will be seen from that curve that one 

 minute after the application of stimulus there is a 

 complete recovery of the tissue ; the molecular con- 

 dition is exactly the same at the end of recovery as 

 in the beginning of stimulation. The second and suc- 

 ceeding response-curves therefore are exactly similar 

 to the first, provided a sufficient interval has been 

 allowed in each case for complete recovery. There is, in 

 such a case, no diminution in intensity of response, 

 that is to say, no 

 fatigue. 



We have an exactly 

 parallel case in muscles. 

 6 In muscle with normal 

 circulation and nutrition 

 there is always an inter- 

 val between each pair of 



,. 7 . . i-L j/ FlG - 20. RECORD SHOWING DIMINUTION OF 



Stimuli, in W/llC/l t/ie RESPONSE WHEN SUFFICIENT TIME is NOT 

 i i. f> . 77 , ALLOWED FOR FULL RECOVERY 



heiqrit of twitch does not , 



In (a) stimuli were applied at intervals of one 



diminish even after pro- minute; in (&) the intervals were reduced to 

 * i half a minute ; this caused a diminution of 



trnrfpfi PVMfnt'in'n n*n/1 response. In (c) the original rhythm is re- 

 TiaCiea eXCltatlOn, ana sto ed , and theVesponseis found to be en- 



no fatigue appears: l 



Apparent fatigue when stimulation frequency in- 

 creased. If the rhythm of stimulation frequency be 

 now changed, and made quicker, certain remarkable 

 modifications will appear in the response-curves. In 

 fig. 20, the first part shows the responses at one minute 

 interval, by which time the individual recovery was 

 complete. 



The rhythm was now changed to intervals of half 



1 Biedermann, Electro-physiology, p, 86. 



(c) 



