21 



of the molecules of the nerves are changed by the dif- 

 ference in the direction of the force, if not, the effects 

 would he the same in both directions, as on a tele- 

 graphic wire, when a message is sent from either tei'min- 

 ation. This difference of effect based upon change of 

 direction is seen in the nervous excitations of sensation 

 and volition. 



To understand what follows, it is therefore necessary 

 to remember that (^ci) what is called "voltaic alterna- 

 tives," is a remarka1)le phenomenon, which is exjierienced 

 when a direct and an inverse current is alternately sent 

 through a section of nerve, it loses and gains its natu- 

 ral electricity, synclironous with the intermissions, and 

 in the same degree as the loss and recovery of it, 

 with irritability. (/*) The influence sent through a 

 nerve causes the muscle in which it ramifies, to contract 

 when the galvanic circuit is closed, and not when it is 

 opened. {(•) A continuous action of magnetism will 

 at last produce paralysis of the part affected — or in 

 other words its ii'ritability is lost, and in this depriva- 

 tion it can no longer receive nor transmit impressions. 

 Did time permit, it could be shown that in these 

 changes we see phenomena that make it possible to ar- 

 rive at rational conclusions in respect to the sudden 

 invasion of such attacks as those of pai'alysis, epilepsy, 

 St. Vitus' dance, hysteria, and allied nervous disorders. 

 To illustrate the nerve influence by what we know in 

 electricity, take two wires and place them parallel to 

 one another, without touching ; send a current through 

 one, and a flash of electricity will instantaneously pass 

 through the other, syncjironous with that in connection 

 with the battery. This wave passes away and is not 

 repeated except the connection is l)roken, when the 

 same results are ol)tained. These intermittent impulses, 

 on connection and breach of continuity, can be repeated 



