Eight lectures on the signs Eight lectures on the signs of life from their electrical aspect eightlectureson00wall Year: 1903 68 THE SIGNS OF LIFE [i for our further experiments, , with its scale to take in a range of about volt. § 42. Summation.—The positive response of the skin is ordi- narily of considerable duration ; in general, the stronger the stimulus, the longer the response ; five minutes has been a very ordinary duration in these experiments. If, then, a second stimulus is applied at the end of one or two minutes, before the first response has fully subsided, we shall obta
Eight lectures on the signs Eight lectures on the signs of life from their electrical aspect eightlectureson00wall Year: 1903 68 THE SIGNS OF LIFE [i for our further experiments, , with its scale to take in a range of about volt. § 42. Summation.—The positive response of the skin is ordi- narily of considerable duration ; in general, the stronger the stimulus, the longer the response ; five minutes has been a very ordinary duration in these experiments. If, then, a second stimulus is applied at the end of one or two minutes, before the first response has fully subsided, we shall obtain a second response superposed on the first, and so on for a third and fourth and n*^ response, which give a summation of effects by successive deflection remainders. Here is a record that will make this point clear. vobt 30 mins. Fig. 31.—Frog's skin. Summating effect of excitation at intervals of 2 mins. (The first response is to a weaker excitation.) With stimuli at shorter intervals, the summation is steeper, and the individual effects of which it is composed may be indistinguishable. There is a fusion of deflections analogous with the tetanic fusion of muscular contractions with which we are all familiar. By reason of this summation, and of the fact that both directions of induction shock arouse response in one and the same (positive) direction, the rapidly alternating currents of an induction coil as ordinarily used for tetanisation give rise to a much larger (positive) response than does a single
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