ELEMENTARY EXPERIMENTAL PHYSIOLOGY 81 



Taking sensation as the index of stimulation, record on the table 

 below the results of the sudden making and breaking of the electric 

 current, and of its continuous flow. 



II. Faradic Current. The Use of the Induction Coil. 



1. Single Induced Shocks. An ordinary type of induction coil or 

 inductorium is shown in Fig. 85. 



Lead off wires from the screw-terminals F on the table (Figs. 



FIG. 85. An induction-coil. 



86 and 87) or from a galvanic cell (Fig. 87) to the screws on the 

 top of the end of the primary coil of an induction coil (Fig. 86), 

 and introduce a mercury key into the circuit. Lead wires from the 



Induction Coll 



~ . ... 

 Sfiortcircuitind 



FIG. 86. Arrangement for single induction shocks, using electrical supply 

 from switch-board. 



terminals of the secondary coil to a friction key, so that when it is 

 closed the current is short-circuited (Figs. 86 and 87). Lead off the 

 wires of a pair of pin electrodes from this key. Pull the secondary 

 coil well away from the primary, open the friction key, so that the 



G 



