Page:Collected Physical Papers.djvu/335

Rh steam, with consequent rise of temperature, there was a transitory augmentation of excitability. But this quickly disappeared, and in five minutes the response disappeared with the death of the plant (fig. 90).

The most important test by which vital phenomena are differentiated is the influence of narcotics and poisons on response. I have already shown how plants which previously gave strong response, did not, after application of an anæsthetic or poison, give any response at all. In those cases it was the last stage only that could be observed. But it appeared important to be able to trace the growing effect of anæsthetisation 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 interrupting this procedure, the anæsthetic agent, chloroform vapour, was