CHEMICAL REAGENTS ON LONGITUDINAL RESPONSE 1 33 



I may here draw attention to the great advantage offered 

 by the study of the variation of longitudinal response, in 

 determining the nature of the action of various chemical 

 agents. The modifications which these agents produce in 

 the lateral response of the pulvini of sensitive plants are 

 not so simple, inasmuch as we have to deal in these cases 

 with differential action. In radial organs, on the other 

 hand, the response-record gives us indications of the specific 

 action of each modifying agent. In the response itself there 

 are, it must be remembered, two factors which have to be 

 distinguished, namely, contraction in response to stimulus, 

 and the power of recovery from contraction, or relaxation. 

 The diminution and final abolition of response may be 

 brought about, then, in two different ways. The effect of a 

 given agent may be to diminish the normal relaxation which 

 brings on recovery. Succcosive stimuli will in that case 

 produce a cumulative residual contraction, which places the 

 tissue in a state of strain, in consequence of which subsequent 

 responses become enfeebled. We may, on the other hand, 

 have an agent whose effect is to produce abnormal relaxation. 

 The contractile impulse due to stimulus is in this case 

 opposed by the abnormal relaxation induced by the agent, 

 and we have, in this case also, an enfeeblement and abolition 

 of response. 



The comparison of the time-relations of the normal and 

 modified curves, together with the trend of the base-line up 

 or down, will show the nature of the reaction, in an unmis- 

 takable manner. All these facts are clearly demonstrated 

 in the experiments and curves given below. 



Effect of alcohol. — I shall next describe the action of 

 the vapour of alcohol. Generally speaking, the immediate 

 effect in this case is one of exaltation, though individual 

 idiosyncrasies may sometimes be present, which cause 

 depression from the very beginning. The general effect of 

 this reagent, however, appears to be a prolongation of the 

 period of recovery. So what is gained by brief exaltation 

 is lost again by induced sluggishness. Thus, from the result 



