Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 III.] BLAZE-CURRENTS 47 such; I characterise it, in distinction from the next variety of current that you will witness, as equivocal or antidrome. The current is subsiding, rapidly at first, now more gradually, and more and more so as the spot approaches its zero position, some- times, indeed, we may witness a permanent positive deflection, a current-remainder reminding one of the contraction-remainder of muscle. I will now test the eyeball by an induction current in the VoLb J_ mms. IO /? -
Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 III.] BLAZE-CURRENTS 47 such; I characterise it, in distinction from the next variety of current that you will witness, as equivocal or antidrome. The current is subsiding, rapidly at first, now more gradually, and more and more so as the spot approaches its zero position, some- times, indeed, we may witness a permanent positive deflection, a current-remainder reminding one of the contraction-remainder of muscle. I will now test the eyeball by an induction current in the VoLb J_ mms. IO /? - zooo o mins. 10 20 FlG. 21.—Normal blaze-currents of a frog's eyeball in response to excitation by a single break induction current in the negative or antidrome direction (B - 2000), and in the positive or homodrome direction (B + aooo). positive direction ; so I adjust the compensation and turn a reverser in the induction circuit, send a break induction shock through the eyeball in the positive direction, and unplug the galvanometer. The spot flies off to your right as before. That also has been a blaze-current, of positive direction in response to an induction shock of positive direction ; it is evidently not a polarisation current; I characterise it in distinction from the first variety as unequivocal or homodrome. This, in my opinion, is a cardinal experiment, and when it was deciphered, became sign-post as well as hinge of further and more general investigation. But let us complete the experiment. The eyeball—upon which you saw a moment ago that two very large responses in one and the same direction followed excitation by single break shocks first in one and then in the opposite direction—has been plunged into hot water, , killed and replaced between the electrodes. I repeat the test of a right and left induction shock and no movement whatever of the galvanometer spot is to be detected. The dead eyeball gives no blaze-current.
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