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Rh electric response. In some there is a rapid fatigue, whereas in others there is little fatigue. A more detailed account of these responses and their modifications by anæsthetics, poisons, and other agencies will be found in a subsequent paper.

Nothing has yet been said of the advantage of the electrical over the mechanical method of obtaining response. As has been said before, the mechanical method is limited in its application. A nerve, for example, does not undergo any visible change of form when excited, and its response cannot therefore be detected by this method. But by the electrical method we are able to detect, not only the response of muscles, but also of all forms of living tissue.

The intensity of electrical response is also a measure of physiological activity. When this is diminished by anæsthetics, the electrical responses also become correspondingly diminished. And when the living tissue is in any way killed, the electrical response disappears altogether.

Thus, electrical response is regarded as the criterion between the living and non-living. Where it is, life is said to be; where it is not found, we are in presence of death, or else of that which has never lived: for in this respect there is a great gulf fixed between the organic living and the inorganic or non-living. The phenomena of the inorganic are supposed to be dominated merely by physical forces, while on the other side of the chasm, in the domain of the living, inscrutable vital phenomena, of which electric response is the sign-manual, suddenly come into action.