Eight lectures on the signs Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 IV.] DIRECT EFFECTS 67 volt. The positive response is declining, rapidly at first, then more slowly, and as soon as the spot is fairly steady, I compensate and repeat the excitation in the reverse (ingoing) direction, and, as before, you witness a large positive (outgoing) voit •oa 30 mms. FlG. 30.—Frog's skin. Response to direct electrical excitation. The first deflection is by a standard voltage. The next two small deflections are in response to + and - break
Eight lectures on the signs Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 IV.] DIRECT EFFECTS 67 volt. The positive response is declining, rapidly at first, then more slowly, and as soon as the spot is fairly steady, I compensate and repeat the excitation in the reverse (ingoing) direction, and, as before, you witness a large positive (outgoing) voit •oa 30 mms. FlG. 30.—Frog's skin. Response to direct electrical excitation. The first deflection is by a standard voltage. The next two small deflections are in response to + and - break induced shocks with the coil at 1000 units. The last two large deflections are with the coil at 5000. (The principal 'outgoing' effect is preceded by a brief ingoing effect in the case of ingoing excitation.) deflection, which, although in the direction of a polarisation counter-current, is a blaze-current, like the antidrome blaze- current of the eyeball (p. 47). Indeed, these skin effects are precisely similar to the effects you have already seen in the case of the eyeball. The positive response to positive excita- tion is the unequivocal blaze, the positive response to negative excitation is the equivocal blaze. And to complete the proof, I will kill the skin either with a few drops of mercuric chloride solution, or by plunging it into hot water, and now the skin gives no response at all to either direction of excitation. The spot does not stir. If I unshunted the galvanometer we might see the small polarisa- tion effects that occur with any electrolyte. But this is an unessential point, and we will leave the galvanometer as it is
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