But we may, sometimes at least, by the timely application of a suitable antidote, revive the dying response, as I do now. See how the lethargy of immobility passes away; the electric throb grows stronger and stronger, and the response in the piece of metal becomes normal once more.
There remains the very curious phenomenon, known not only to students of physiological response but also in medical practice, that of the opposite effects produced by the same drug when given in large or in small doses. Here too we have the same phenomenon reproduced in an extraordinary manner in inorganic response. The same agent which becomes a poison in large quantities thus acts as a stimulant when applied in small doses.
I have shown you this evening autographic records of responses of the living and non-living. How similar are the writings! So similar indeed that you cannot tell one from the other apart. We have watched the responsive pulses wax and wane in the one as in the other. We have seen response sinking under fatigue, becoming exalted under stimulants, and being "killed" by poisons, in the non-living as in the living.
Amongst such phenomena, how can we draw a line of demarcation, and say, "here the physical process ends, and there the physiological begins"? No such barriers exist.
Do not the two sets of records tell us of some property of matter common and persistent? Do they not show us that the responsive processes, seen in life, have been foreshadowed in non-life?—that the physiological is, after all, but an expression of the physico-chemical, and that there is no abrupt break, but a continuity?
