472 COMPARATIVE ELECTRO-PHYSIOLOGY 



parallelism is to be observed. The completeness of this may 

 be seen in greater detail in the next chapter. I shall, at the 

 present point, confine myself to giving a few typical cases. 

 Ether, for example, when acting on animal nerve, induces a 

 preliminary exaltation of excitability, which is followed under 

 its long continued action by depression. On blowing off 

 the ether vapour again the original state of excitability is 

 restored. In fig. 280 are seen the similar effects of this 

 reagent on vegetable nerve, where (a) exhibits the normal 

 response, (b) the immediate exaltation due to ether, (c) the 



FlG. 280. Photographic Record of effect of Ether on the Electrical 

 Response of Plant-nerve 



(a) Normal response : application of ether at point marked with f ; 

 (A) Enhanced response in first stage of action of ether ; (c) Subse- 

 quent depression ; (d) Restoration of normal response after blowing-oft 

 of ether. 



subsequent effect of depression, which becomes marked after 

 continuous action during twenty-five minutes, and (d) the 

 restoration of the original condition on the blowing-off of 

 the ether. 



Carbonic acid is known, in the case of animal nerve, to 

 have the effect, in the first stage, or in small quantities, of 

 inducing exaltation, which passes under its prolonged action, 

 or, in the case of a stronger application, into depression. A 

 similar effect is seen in fig. 281, where (a) shows the normal 

 response of a vegetable nerve, and (b) the preliminary exalta- 

 tion due to carbonic acid introduced into the vegetable nerve- 



