Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 170 PHYSIOLOGY We find experimentally that this indijfferent point is nearer the anode when the polarising current is weak, and gets nearer to the kathode as the current is strengtliened, so that with very strong currents nearly the whole intrapolar Fir,. 78. Diagram to show the variations of irritability in a nerve during the passage of polarising currents of different strengths. The degree of change is represented by the distance of the curves from the base line ; the part of the curve belo
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 170 PHYSIOLOGY We find experimentally that this indijfferent point is nearer the anode when the polarising current is weak, and gets nearer to the kathode as the current is strengtliened, so that with very strong currents nearly the whole intrapolar Fir,. 78. Diagram to show the variations of irritability in a nerve during the passage of polarising currents of different strengths. The degree of change is represented by the distance of the curves from the base line ; the part of the curve below the line signifying den-ease, that above the line increase of irritability. A, anode; B, kathode; 7/1, effect of weak current; ?/.„ medium current; y.^, strong current. It will be noticed that the indifferent point, ,r, where the curve crosses the horizontal line, approaches nearer and nearer the kathode as the current is increased in strength (from Foster, after Pfiiiger). length is in a condition of anelectrotonus (Fig. 78). When a strong polarising current is used, the depression of irritahility at the anode is so marked that no impulse can pass this region. Thus if we send a very strong ascending current Fig. 79. ascendinq current kath. an. make excitation blocked at anode. kath. break excitation at anode blocked at kathode. Diagram to show the blocking effect of a strong constant current passed through the nerve of a nerve-muscle preparation. through the nerve, there is no contraction at make. This is owing to the fact that the impulse started at the kathode on make of the current cannot reach the muscle, its passage down the nerve heing hlocked in the region of the anode (Fig. 79, A).
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