Fig. 135. 



ANIMAL AND VEGETABLE 243 



German silver has a low co-efficient 

 of increase of resistance with temperature, 

 and, when heavily plated, is a very suitable 

 alloy. 



When one of these electrodes is held in each hand by the 

 patient the thumbs are pushed up to the closed ends of 

 the thumb-pieces, the fingers used merely in support and 

 no pressure exercised. The connections are then 



Galvanometer 



Jflectrodeh j 



f ' 



^~oL/^ 



Fig. 136. 

 Short-circuit key omitted. 



The other electrodes consist of an elastic rubber band, to 

 encircle the head, carrying a circular plate of silver (or 

 German silver heavily plated) 1 in. in diameter and 

 provided with a terminal of the same metal : 



Fig. 137. 



For purposes of electro-diagnosis this is connected by a wire 

 to one terminal of the galvanometer, and the band fitted 

 round the head of the patient in such manner that the flat 



