Electricity and Galvanism. 



259 



Now as the iodine is invariably liberated at the place where positive 

 electricity enters the body containing it, we have a proof of the 

 accuracy of the statement I made, that positive and negative elec- 

 tricity were alternately evolved at both wires. On this account, 

 however useful this apparatus is when we want the mere stimulant 

 action, the simple shock of the electric agent, yet it is likely to 

 fail in many cases of paralysis, in consequence of our not being able 

 to transmit by its aid the positive current in the direction of the 

 nervous ramifications. 



The more elegant and elaborate magneto-electric machine, especi- 

 ally the very effective and powerful one of Mr. Clark's construction, 

 may of course be substituted for the electro-magnetic apparatus I 

 have described. The advantages it presents of being always ready 

 for use, and requiring no initial voltaic current to set it in action, are 

 not, however, I think by any means sufficient to compensate for 

 its expense, and the readiness with which it is disarranged, especial- 

 ly when in the hands of the uninitiated. 





A. The revolving cylinder, with slips of brass inlaid, on which the springs 

 B. B. press. 



C. The battery, connected by wires with the screws D. E. F. F. ; the con- 

 ductors, connected with the screws G. G., which are in communication 

 with the fine coil in the box K. 



To render the electro-magnetic current available where it is required 

 to be transmitted in a definite direction, — where, indeed, we want the 

 currents separated as we get them in the voltaic or galvanic battery, 

 without the serious inconvenience attending the use of these pieces of 

 apparatus, — some modification of the electro-magnetic machine is 



