PLANTS UNDER MECHANICAL STIMULUS, 301 
died only after various indirect signs have begun to appear. 
But in the electric response we have an immediate indication of 
the arrest of vitality, and are thereby enabled to determine 
the death-point, which it is impossible to do by any other 
means. 
Liffects of Anesthetics and Poisons. 
The most important test by which vital phenomena are 
differentiated is the influence on response of narcotics and 
poisons. I have already shown how plants which previously 
gave strong response, did not, after application of an anzsthetic 
or poison, give any response at all. In those cases it was the 
last stage only that could be observed. But it appeared im- 
portant to be able to trace the growing effect of anesthetisation 
or poisoning throughout the process. 
Effect of Chloroform.—The mode of experiment was (1) to 
obtain a series of normal responses to uniform stimuli, applied 
at regular intervals of time, say one minute, the record being 
taken the while on a photographic plate. (2) Without in- 
lerrupting this procedure, the anesthetic agent, chloroform 
vapour, was blown into the closed chamber containing the plant. 
It will be seen how rapidly chloroform produces depression 
of response and how the effect grows with time (fig. 24). 
Fig. 24. 
Before (8), * After (11). 
| 
Effect of chloroform. 
Exactly similar effects were obtained with chloral, also with 
formalin. These were applied in the form of solution on the 
