EXCITABILITY UNDER CHEMICAL REAGENTS 131 



cases of liquid reagents, they are applied on the points of 

 contact A and B, and in their close neighbourhood. The 

 experiment is carried out by first obtaining a series of 

 normal responses to uniform stimuli, applied at regular 

 intervals of time, say one minute, the record being taken the 

 while on a photographic plate. Then, without interrupting 

 this procedure, the given agent say, vapour of chloroform 

 is applied, by being blown into the chamber. It will be seen 

 from fig. 84 how rapidly chloroform induces depression of 

 response, and how the effect grows with time. If the speci- 

 men be subjected for a short time only to the anaesthetic, 

 the depressing action proves transient, passing off on 

 the reintroduction of fresh air. But too strong or too pro- 

 longed an application induces a permanent abolition of 

 response. 



I give below (figs. 90, 91), two sets of records, one of 

 which shows the effect of chloral and the other formalin. 



Before 



After 



FIG. 90. 



Photographic Record showing Action of Chloral Hydrate on the 



Responses of Leaf- stalk of Cauliflower 

 Torsional vibration of 25 at intervals of one minute. 



These reagents were applied as solutions on the tissue at 

 the two leading contacts and adjacent surfaces. Both 

 are seen to induce a rapid decline of the response. In the 



K 2 



