26 RESPONSE IN THE LIVING AND NON-LIVING 
another point has to be borne in mind. In all cases of 
stimulation of living tissue it is found that the effective- 
ness of a stimulus to arouse response depends on the 
rapidity of the onset of the disturbance. It is thus 
found that the stimulus of the ‘ break’ induction shock, 
on a muscle for example, is more effective, by reason 
of its greater rapidity, than the 
‘make’ shock. So also with the 
torsional vibrations of plants, I find 
response depending on the quickness 
with which the vibration is effected. 
a 6 ¢ d— J give below records of successive 
=> 
Fic. 13.—Ineuvence Stimuli, given by vibrations through 
oF SUDDENNESS ON the same amplitude, but delivered 
THE EFFICIENCY OF 
STIMULUS with increasing rapidity (fig. 13). 
The curves a, b, c,d, are é 3 z - 
responses to vibra- Thus if we wish to maintain the 
tions of the same 
amplitude, 80°. In effective intensity of stimulus con- 
a the vibration was 
very slow; in b it gtant we must meet two conditions: 
was less slow; it was : ve a 
rapid in c,and very (J) The amplitude of vibration must 
rapid in d. a 
be kept the same. This is done by 
means of the graduated circle. (2) The vibration period 
must be kept the same. With a little practice, this 
\ 
requirement is easily fulfilled. 
The uniformity of stimulation which is thus attained 
solves the great difficulty of obtaining reliable quan- 
titative values, by whose means alone can rigorous 
demonstration of the phenomena we are studying 
become possible. 
