General physiology of muscles and nerves . f some conductingsubstance, such as copper,and its circumference is cutinto teeth like that of theratchet-wheel of a copper wire rests onthis circumference. Theaxis of the wheel and the 7 , 1 ..1 Ilt;- 11. Electric Wheel. Wire 0 are connected with the conducting wires by means of the screws d and /.When the click rests on one tooth of the circumferenceof the wheel, the current is enabled to pass throughthe wheel, and thus also thi-ough coil A ; it is, how-ever, interrupted during the interval which interveneswhile the click springs from one
General physiology of muscles and nerves . f some conductingsubstance, such as copper,and its circumference is cutinto teeth like that of theratchet-wheel of a copper wire rests onthis circumference. Theaxis of the wheel and the 7 , 1 ..1 Ilt;- 11. Electric Wheel. Wire 0 are connected with the conducting wires by means of the screws d and /.When the click rests on one tooth of the circumferenceof the wheel, the current is enabled to pass throughthe wheel, and thus also thi-ough coil A ; it is, how-ever, interrupted during the interval which interveneswhile the click springs from one tooth to the , by turning the wheel on its axis the currentin coil A is alternately closed and opened. Conse-quently, inductive currents constantly occur in theadjacent coil B, and these pass in rapid successionthrough the muscle. Each of these currents irritatesthe muscle; and since they occur in such quick suc-cession, the muscle has no time to relax in the inter^?a]s,but continues permanently contracted. Enduring con-3. 34 PHYSIOLOGY OF MUSCLES AND NERVES. traction of this sort is called tetanus of the muscle todistinguish it from a series of distinct pulsations. Another method of frequently and repeatedly clo-sing and opening the current is by means of a self-acting apparatus which is put in motion by the currentitself. This, which is called Wagners hammer, is re-presented in fig. 12. The current of the chain is con-ducted through the columnrepresented on the right tothe German silver spring o small platinmn plate c issoldered on to the latter, andis pressed against the pointabove it by the elastic forceof the spring. The currentpasses from this to the coilsof a small electro-magnet,and, after passing throughthis, back to the chainthrough the clamp connected with it on the left. Anarmature of soft iron, «, fastened on to the springo o, is suspended over the poles of the iron being attracted by the electro-magnet, thesmall plate c is f
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