ELECTRIC RESPONSE 5 
say, I desired to know, with regard to plants, what was 
the relation between intensity of stimulus and the cor- 
responding response; what were the effects of super- 
position of stimuli; whether fatigue was present, and 
in what manner it influenced response ; what were 
the effects of extremes of temperature on the response ; 
and, lastly, if chemical reagents could exercise any in- 
fluence in the modification of plant response, as stimu- 
lating, anesthetic, and poisonous drugs have been found 
to do with nerve and muscle. 
If it could be proved that the electric response 
served as a faithful index of the physiological activity 
of plants, it would then be possible successfully to 
attack many problems in plant physiology, the solution 
of which at present offers many experimental difficul- 
ties. 
With animal tissues, experiments have to be carried 
on under many great and unavoidable difficulties. The 
isolated tissue, for example, is subject to unknown 
changes inseparable from the rapid approach of death. 
Plants, however, offer a great advantage in this respect, 
for they maintain their vitality unimpaired during a 
very great leneth of time. 
In animal tissues, again, the vital conditions them- 
selves are highly complex. Those essential factors 
which ,modify response can, therefore, be better deter- 
mined under the simpler conditions which obtain in 
vegetable life. 
In the succeeding chapters it will be shown that the 
response phenomena are exhibited not only by plants 
but by inorganic substances as well, and that the 
