268 



Dr. N. H. Alcock. 



[Nov. 9, 



polarisable electrode, while another electrode rests on an uninjured 

 longitudinal surface, the galvanometer will indicate a difference of potential 

 which declines at a certain rate. This can be measured either by photo- 

 graphing the movement of the galvanometer spot, or, more accurately, by 

 balancing against a known potential, reading the potentiometer at convenient 

 intervals of time, and plotting the figures on squared paper; this latter 

 method eliminates any change in the resistance of the object. The curve 

 obtained is concave to the abscissae, neglecting a variation which is occasionally 

 found during the first five minutes of the experiment. 



If, when this curve has assumed a typical form, CHC1 3 vapour be applied 

 to the nerve, a sudden drop is observed. If the vapour is weak, this is 

 followed by a recovery when the CHC1 3 is removed, if the vapour is strong 

 (12 per cent, or over) the drop is permanent (fig. 1). This may be due 



200 

 190 

 180 



160 

 150 

 140 

 130 

 120 



no 

 IOO 

 30 

 80 

 70 

 60 

 50 

 40 

 30 

 zo 



10 



o 

 10 

 zo 



(106) 



Exp. 11 



Fig. 1.— Sciatic of Frog. CHC1 3 vapour at 12 - 5 per cent, between the vertical bars. 

 Ordinates 1 mm. = O'OOOl volt. Abscissae 1 mm. = 15 seconds. 



