. A class book of (elementary) practical physiology : including histology, chemical and experimental physiology. Physiology. BREAK EXTRA CURRENTS. 191 It is well. also. t>> bear in mind that contact- are by no moans of negligible duration, for they vary very much in different forms of instruments. This applies also to ordinary keys. These are the salient features in the action of the Induetorium, but there .ire others, such as the influence of the electromagnet of the interrupter, dfcc, which cannot he considered here. Demonstration of the break extra current as an illustration of one of
. A class book of (elementary) practical physiology : including histology, chemical and experimental physiology. Physiology. BREAK EXTRA CURRENTS. 191 It is well. also. t>> bear in mind that contact- are by no moans of negligible duration, for they vary very much in different forms of instruments. This applies also to ordinary keys. These are the salient features in the action of the Induetorium, but there .ire others, such as the influence of the electromagnet of the interrupter, dfcc, which cannot he considered here. Demonstration of the break extra current as an illustration of one of the induction effects in the P coil (Fig. '27). Remove the S coil from the Induetorium and set up as follows: First set up the Leclanehe cell in circuit with the hand electrodes with a "shorting" key (1). Hold the electrodes against your tongue, and open and close the key—nothing will be felt. The of the current is not sufficient to produce a stimulus through the resistance offered by the skin. Now add to the battery circuit the P coil (slip off the S coil and place it on one side) with shorting key (2), so that the P coil may be at will in- or excluded from the circuit. Keep key (2) closed, and repeat the trial as before, key ^2) excludes the coil from the circuit and the result is the same (effect of *'shorting"). Xext open key (2). then on opening key (Da shock is felt at break. This shock is due to the induction current which is generated in the coil by the fall of potential in the battery circuit. The fall is due to the easier path through key (1), being replaced by a path of greater resistance through the tongue, and consequently a feebler current flows through the P circuit, and this drop generates an induction current in the circuit, and the latter having a higher , is able to pass through the tissues and to act as a stimulus. The effect is largely due to the iron cove of the coil, for if the S coil be sub- stituted the effect mil not be s
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