. The dynamics of living matter . lOO DYNAMICS OF LIVING MATTER ing or a much weaker one occurs when a spark is produced. The same effect can be produced when a Rumkorff induction apparatus is used in place of a Toepler-Hokz machine. The explanation of the experiment is as follows: let us assume that at a given moment the electrode a (Fig. i6) be charged positively and h negatively; in this case the nerve will possess at c a negative, at d a positive charge. As soon as the spark passes, the charges in the nerve will disappear also; a current will go lengthwise through the nerve, and a twitchin
. The dynamics of living matter . lOO DYNAMICS OF LIVING MATTER ing or a much weaker one occurs when a spark is produced. The same effect can be produced when a Rumkorff induction apparatus is used in place of a Toepler-Hokz machine. The explanation of the experiment is as follows: let us assume that at a given moment the electrode a (Fig. i6) be charged positively and h negatively; in this case the nerve will possess at c a negative, at d a positive charge. As soon as the spark passes, the charges in the nerve will disappear also; a current will go lengthwise through the nerve, and a twitching will result. If, however, the nerve is placed at right angles to the spark discharge and symmetrical in regard to the two electrodes (Fig. 17), the current must go crosswise through the nerve, and no effect or only a minimal effect ensues. In this experi- ment no electrical charges are withdrawn from the ions, and the only effect of the current exists in a change in the concentration of the ions at various places in the nerve. Since, however, in this case of stimula- tion of the nerve by induction, the effect is the same as in the case of a direct application of the electrodes to the nerve, we must draw the con- clusion that in the latter case also the change of concentration is suffi- cient for the physiological effect, and that the withdrawal of the charge from the ion cannot be the cause. Nernst has tested the idea that the electrical current only stimu- lates the nerve by bringing about changes in the concentration of ions at various places in the nerves.* It had been known for some time that the interrupted current is an excellent medium for stimulating nerves or muscles, and it was also generally known or accepted that alternating currents produce only weak effects when the number of alternations becomes very high. Quantitive determinations had also shown that the minimum intensity of an alternating current which is required to bring about tetanus, increases with the nu
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