320 



BKNJ. PIKE S, JR., DESCRIPTIVE CATALOGUE. 



ors are for two purposes ; first, that by means of their balls 

 they shall be able to direct the fluid, or shock, to any par- 

 ticular part only, and confine it thereto, as in the following 

 cut (Fig. 376) ; the shock may be given from the knee to 

 the foot without its affecting the rest of the body. 



Fig. 375. Fig. 376. 



The use of the glass handles is to prevent the operator 

 from participating in the shock he intends for his patient. 

 The operator, of course, holds the glass handles, while the 

 balls are made to touch the extreme points of that line 

 through which the shock is to pass. One director is usually 

 straight, and the other bent. We will now suppose that 

 the ball, E, of the electrometer has been placed so as to 

 touch the conductor, the whole apparatus being dry, and in 

 good working order ; and indeed that the whole is as repre- 

 sented in the cut ; the knobs of the directors touching, and 

 the wires, A and B, being in their place. Turn the machine 

 and the bottle will not charge, because the outside is in close 

 contact with the inside, there being no interruption in the 

 circuit anywhere. Now remove the ball, E, a short space 

 from D ; upon turning the machine a second time, the bottle 

 will become charged, because its inside is not connected by 

 conducting substances with its outside. A vacancy occurs 

 between D and E, and exactly in proportion to the size of 

 that vacancy will be the strength of the shock which passes 

 through the chains, or the balls of the directors ; and as 

 those balls are applied to different parts of the body, so of 

 course will be the strength of the shock which will be felt. 

 The above supposes that both wires are in the bottle ; now 

 if we draw out the longer wire, the only one left will be that 



