RESPONSE OF ISOLATED VEGETAL NERVE 



473 



chamber. This is seen to increase continuously for some 

 twenty minutes in (c). But after the expiration of half an 

 hour depression makes its appearance (d). This becomes still 

 more marked, after the fortieth minute, in (e\ 



FIG. 281. Photographic Record of Effect of CO 2 on Electrical 

 Response of Plant-nerve 



a, normal responses ; b and c, enhanced response during first stage of 

 action ; d and e t subsequent growing depression. 



Alcohol vapour in strong, or long-continued applications, 

 induces marked decline of response in animal nerve. Parallel 

 effects are seen in the case of vegetable nerve in fig. 282. 



The effect of ammonia on animal tissues is character- 

 istically different, according as the subject of experiment is 





FIG. 282. Photographic Record of Abolition of Response by Strong 

 Application of Alcohol 



nervous or ordinary tissue. While the excitability of the 

 muscle, for example, is but little affected by its application, 

 that of nerve is quickly abolished. In order to see whether 

 the same characteristic difference would be exhibited, as 



