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compound. In the last case, however, while intensity is 

 needed to overcome chemical attraction, quantity is required 

 to regulate the amount decomposed. 



In using the primary coil machine, it is supposed that when 

 the human body is made a part of the circuit, the current from 

 the battery, together with the induced current obtained on 

 breaking contact, passes through the body, and that the cross 

 current on making contact is cut off; likewise, that as the 

 number of batteries is increased the quantity of electricity 

 passed is augmented. To both of these opinions he dissented. 

 That this apparatus is advantageous he admitted, but he de- 

 nied its effecting the passage of the battery current through 

 the body. Its advantage solely consisted in the fact that the 

 cross current arising on making contact, is conveyed across 

 the spring back to the battery, the two collateral currents 

 passing through the patient in one direction whenever con- 

 tact is broken, the shocks depending upon the induced in- 

 tensity current. When, for example, the handles of a simple 

 primary coil are grasped, and contact made with the continua- 

 tion of the wire, an induced current is felt in breaking con- 

 tact ; but if the body be included in the circuit, between the 

 battery and the coil, by holding one hand attached to the coil, 

 and with the other making contact, no secondary current is 

 induced, because the battery circuit is not completed by the 

 body so as to allow the current to pass and produce its induc- 

 tive effects. Neither does decomposition of Iodide of Potas- 

 sium — a salt very easily decomposed — take place if the body 

 is included in the circuit, the quantity of electricity being too 

 small to effect electrolysis ; nevertheless the intensity is suffi- 

 cient to effect decomposition were quantity present, for power- 

 ful shocks are felt on making and breaking contact in the 

 usual way. Besides these proofs, he had failed to detect any 

 indication of the passage of the current by the galvanometer, 

 excepting when he employed a very large coil and batteries, 

 exposing an active surface of about one hundred and twelve 



