CHAPTEE IX 



PLANT KESPONSE EFFECT OF ANAESTHETICS AND POISONS 



Effect of anaesthetics, a test of vital character of response Effect of chloro- 

 form Effect of chloral Effect of formalin Method in which re- 

 sponse is unaffected by variation of resistance Advantage of block 

 method Effect of dose. 



THE most important test by which vital phenomena are 

 distinguished is the influence on response of narcotics 

 and poisons. For example, a nerve when narcotised 

 by chloroform exhibits a diminishing response as the 

 action of the anaesthetic proceeds. (See below, fig. 43.) 

 Similarly, various poisons have the effect of permanently 

 abolishing all response. Thus a nerve is killed by 

 strong alkalis and strong acids. I have already shown 

 how plants which previously gave strong response did 

 not, after application of an anaesthetic or poison, 

 give any response at all. In these cases it was the last 

 stage only that could be observed. But it appeared 

 important to be able to trace the growing effect of 

 anassthetisation or poisoning throughout the process. 

 There were, however, two conditions which it at first 

 appeared difficult to meet. First it was necessary to 

 find a specimen which would normally exhibit no 

 fatigue, and give rise for a long time to a uniform series 



