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But the modification of which I have spoken does not stop short of mere abolition of responsive power, but sometimes proceeds further, and actually reverses the sign of response—the excited wire becoming cuproid.

But even in such cases long-continued stimulation transfonms the abnormal negative to the normal positive. I give below photographic records which exhibit this. In fig. 78, α, the transformation took place during continued vibration. To detect the point of transformation, I experimented with a platinum cell which exhibited the abnormal effect, and took a long series of records of responses to uniform stimulation acting at

intervals of a minute. In the record (fig. 78, β) I have been able to catch the point or rather points of transition.

Abnormal response of animal nerve.—It is interesting to note that similar abnormal response 18 also exhibited