EFFECTS OF ANODE AND KATHODE 235 



animal. In the case of the Dcsmodium leaflets the pulsations 

 are seen to take place in a very regular manner, the period 

 of one complete pulsation being about 3 minutes. Of the 

 up and down movements of the leaflet, the down movement 

 takes place more quickly, corresponding to the systolic con- 

 traction of the rhythmic cardiac tissue. The systolic move- 

 ment in Desmodium takes place in the course of about 

 1 minute and 10 seconds, the slower diastolic expansion being 

 accomplished in the course of about 1 minute and 50 seconds. 

 In the record, the quicker systolic movement is represented 

 by the up-curve. The extent of contraction is thus repre- 

 sented by the upper limit of the curve of response ; the lower 

 limit indicates the extent of diastolic expansion. If the 

 leaflet is executing its greatest possible amplitude of pulsa- 

 tion, then an external agent will be unable to increase it 

 any further ; but the extent of contraction or expansion 

 can be individually reduced under agencies which have an 

 opposing tendency. Thus if the continuation of anode tends 

 to induce expansion, then during a cycle of pulsating 

 activity it would oppose the contraction at the systolic 

 phase. The effect would be a diminution of contraction ; 

 in the record this would appear as progressive diminution 

 of heights of responses. 



If the application of kathode, on the other hand, induces 

 contraction, this would oppose the diastolic expansion ; the 

 amplitude of pulsation will be progressively diminished, 

 with continuously diminishing relaxations, and the base-line 

 would be shifted upwards. 



In order to demonstrate these contrasted polar reactions 

 the experiment was carried out by making the pulvinule of the 

 leaflet alternately anode or kathode. One electric connection 

 is made with the pulvinule by means of a thin thread, 

 special care being taken that this in no way interfered with 

 the free pulsation of the leaflet ; the second connection is made 

 with an indifferent point lower down in the petiole. 



I shall first describe the expansive effect of anode-make 

 and the contractile effect of kathode-make ; these particular 



