PRACTICAL PHYSIOLOGY 25 



2. That an induction shock is a stimulus, and 

 that the break induction shock is a far stronger 

 stimulus than the make induction shock. Get the 

 minimal effect of each by sliding the secondary 

 coil to the necessary distance from the primary, 

 and make notes as to the respective positions of 

 the secondary coil. 



3. That it is possible to stimulate the nerve when 

 it is connected by only one wire with the secondary 

 coil ; hence the necessity for using a short-circuit 

 key to prevent unipolar induction. It is best for 



FIG. 25. STIMULATION OF NERVE BY CONDENSER DISCHARGE. 



this experiment to place the secondary coil at zero 

 and to make use of the automatic interrupter (Fig. 

 1 8). The nerve should be raised up from the wet 

 blotting paper. 



4. That the discharge of a condenser through a 

 nerve also acts as a stimulus. Arrange the appa- 

 ratus as shown in Fig. 25, in which C is a condenser 

 made by covering a sheet of glass with tinfoil on 

 both sides. The sheets of tinfoil are first connected 

 with a battery, and then, by turning the switch, are 



