346 APPENDIX. 



the lever is put down (arrangement of key to break 



the current) ; lastly, if the wires from the battery are 

 connected with a and b respectively, and the wires 

 of the electrodes with a and c respectively, then the 

 current passes across the key until the end x of the 

 lever is pressed down when the current is thrown 

 into the electrodes (arrangement of key for short- 

 circuiting the current) 



du Bois Reymond's Induction Machine. This is 



shewn at Z>, Fig. 1. The screws at the top of the 

 machine are connected with the ends of the wire 

 forming the primary coil; consequently, when the bat- 

 tery wires are connected with these screws, each break 

 and each make of the circuit produces an induction 

 current in the secondary coil ; the make and break 

 can be most simply effected by means of a key 

 placed in the primary circuit and arranged to break 

 the current (cp. above); in the text this is called the 

 arrangement for single induction shocks. 



When the wires from the battery are connected with 



