Fig. 48. — Tlic non-polarizable electrodes I'oi- the linger li().s with means of controlling the 



temperature. 



The natural and comfortal)lc position of the sul)ject's hand is evident. 



Fig. 49. — Apparatus for controlling the voltage of the shocks and for intermittently short- 

 circuiting them. 



D, drop wire across 220 volts; V, voltmeter of standard make; R, 200,000 ohms resistance; C, 

 control switch; B and B', vacuum bulbs (parts of control switch), each containing 1 c.c. of 

 mercury, which are noiselessly tipped back and forth to make and break the circuit. S, con- 

 veniently placed cord for operating C in breaking the circuit; a spring not visible in the 

 illustration exerts tension on C in the opposite direction from S. The hands of the operator 

 are shown in position for taking electrical threshold measurements. 



