136 



COMPARATIVE ELECTRO-PHYSIOLOGY 



The specimen employed was the petiole of fern. The thermal 

 stimulator was at a distance of 1-5 cm. from the proximal 

 electrode. In fig. 94 is shown the stimulating action of a 



FIG. 94. Photographic Record showing the Stimulatory Action 

 of Solution of Sugar 



2 per cent, solution of sugar, inducing a continuous enhance- 

 ment of response for some time. 



Another stimulating agent is a dilute solution of Na 2 Co 3 . 

 This when applied in I per cent, solution induces an 



FlG. 95. Photographic Record showing Continuous Action of 

 2 per cent. Na 2 CO 3 Solution 



Preliminary exaltation followed by depression. 



enhancement of amplitude of response, but when given in 

 strong solution, induces depression. An intermediate strength 

 of solution shows preliminary enhancement followed by de- 

 pression (fig. 95). 



