1 8 PRACTICAL PHYSIOLOGY 



ing K* the stimulus is hardly perceptible to the 

 tongue. 



6. Instead of placing the simple key in the pri- 

 mary circuit place it in a side circuit (Fig. 21). On 

 closing and opening the key, shocks are still pro- 

 duced in the secondary circuit, although the current 

 through the primary coil is not made and broken, 

 but only strengthened and weakened. The make 

 and break shocks in the secondary coil are now 

 more uniform, but are both weaker. 



7. Take the secondary coil out and place it across 



FIG. 21. INDUCTION EFFECTS OF CLOSING AND OPENING A SIDE CIRCUIT CONNECTED 

 WITH PRIMARY COIL. 



the direction of the primary coil instead of in its 

 usual position. The making and breaking of the 

 primary circuit now produce no effect on the 

 secondary circuit, but induced currents begin to 

 show themselves if the secondary coil is placed 

 obliquely to the primary, and are strongest when 

 the two coils are again parallel. 



8. Connect up the battery with the terminals, 

 7" 3 , 7" 4 , of the induction coil (as in Fig. 18), intro- 

 ducing a simple key into the circuit. Set the 



