NEW CLASSES OF GALVANIC CONDUCTORS. 245 



Be this as it may, to prevent any mistake from creeping in, Farther pre- 

 if the contact of the insulated conductor, which terminates cautions « 

 at one extremity in the flame, and at the other at the nerves, 

 produce a contraction during the period of the highest irri- 

 tability, a few moments should be suffered to elapse, the 

 application of the insulated exciter should be repeated from 

 time to time, and very soon the application will produce no 

 effect. The experiment then properly commences. In fact, £ xper i ment . 

 when the insulated exciter has no physiological action, it is 

 sufficient to establish a communication between it and the 

 ground, either by touching it with the finger, or taking it 

 in the hand without the insulating handle, and very strong- 

 contractions will be produced every time the circuit is com- 

 pleted from the flame to the nerves. The influence of the 

 ground may be proved, by completing the circuit with an 

 insulated and an uninsulated arc alternately. If a certain 

 interval be allowed between these comparative applications, 

 those with the insulated arc will never produce any effect, 

 those with the uninsulated will constantly excite contractions. 

 } must observe, however, that this kind of galvanic excite- The irritability 



jment, by the intervention of flame and the mound, requires of the &ub J ect 

 i .,...., 1 must be great. 



a much greater excitabdity in the subject, than the common 



method of completing the circuit immediately from pole to 

 pole; for the muscles are obedient to the latter, long after 

 they have ceased to contract by the application of an un- 

 insulated conductor to the flame. It is to be understood, When placed 

 however, that, if the prepared muscles be placed on the po- u've^Vle^no 

 sitive pole, and the circuit then be completed from the effect is pro- 

 flame to the nerves, no effect will be obtained, whether the duced * 

 arc be insulated or uninsulated; for, as the flame belongs 

 exclusively to the positive pole, it is obvious, that it cannot 

 produce contractions with the pole of its own nature. 



The explanation of this fact appears to me to arise na- The fact ex- 

 turally from what has been said. The flame insulates all P laiaed - 

 negative effect, and consequently cannot complete the gal- 

 vanic circuit. But in the application of the uninsulated arc 

 between the flame and the nerves, it is properly the ground 

 that serves as an intermediate chain, and the mind may dis- 

 tinguish three different effects at the same instant of time. 

 The first is that of charging the negative pole to a maximum 



at 



