APPENDIX 



THE USE OF ELECTRICITY FOR STIMULATING IN 

 PHYSIOLOGY AND MEDICINE l 



(The Student should revise his knowledge of Electricity.) 



Sources of Electricity most Generally Used. In hospitals the town 

 supply of electricity is generally used either directly, the voltage 

 being reduced by means of a resistance, or better by a motor gener- 

 ator, or indirectly by charging accumulators. 



The wires used to lead off the current are connected with screws 

 upon a SWITCH-BOARD. There are generally two sets of terminals, 

 one for using the galvanic current, one for using the faradic. 



In some physiological laboratories a similar installation is used. 1 



Electrocles 



' Key- 



FIG. 73. Simple Galvanic Current. 



Fig. 73 shows a simple form of switch-board with terminals G + 

 and (anode and cathode) for using the galvanic current ; ter- 

 minals F for using the faradic current, and terminals T for recording 

 intervals of time. These last are connected with a wheel chrono- 

 graph, driven by a motor, which can be set to give intervals of ^th 

 or 1 second. 



1 In the University of Glasgow the current is supplied from an accumu- 

 lator giving from 15 to 30 volts to the switch-boards on the tables. The 

 terminals on the switch-board marked G are for galvanic stimulation, and 

 give from to 400 milliamperes. The lever regulator on the switch-board 

 controls the strength of the current (from the G terminals only). When 

 placed at W it gives the weakest current, when moved towards S it 

 gives the strongest current. The terminals marked F are for Faradic 

 stimulation, and give about 1-5 amperes. The terminals marked T are 

 connected with a chronograph and interrupt at 1 sec., or 0-1 sec., according to 

 the way in which the instrument is set. 



77 



