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 inmuscles. 
Lita dt 
“In muscle with normal 
Boe Yeu e 
RUCRUUINUY 
circulation and nutrition 
there is always an inter- 

val between each pair of (a) ) ©) 
F : . 2 Fic. 20.—Recorp sHowinc DIMINUTION oF 
stimult, in which the RESPONSE WHEN SuFFIcIeNT TIME Is NoT 
° > . ALLOWED FoR Fut Recovery 
height of twitch does not iets. sist ee 
In (a) stimuli were applied at intervals of one 
diminish even after pro- minute; in (0) the intervals were reduced to 
half a minute; this caused a diminution of 
tracted excitation and response. In (c) the original rhythm is re- 
v 4 / 49 L 
stored, and the response is found to be en- 
no fatigue appears.’ | Bees haha sv ya 
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 
" Biedermann, Electro-physiology, p. 86. 
