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MULTIPLE AND AUTONOMOUS ELECTRICAL RESPONSE 217 



waves of electrical response was slightly less than i minute, 

 and that of the subsidiary wave a little over 2-5 minutes. 

 These double electrical pulses, corresponding to a single 

 .mechanical vibration, are at first very puzzling, and I under- 

 took special investigations to ascertain the reason of this 

 peculiarity. In order to obtain an insight into the relation 

 between these mechanical and electrical responses it was 

 necessary to take simultaneous records of the two on the 

 same recording drum. This was accomplished by having 

 the two recording spots of light one from the galvanometer 

 and one from the optic lever thrown on the same horizontal 

 slit, in front of the revolving drum, round which was wrapped 

 sensitive photographic film. The galvanometer spot of 



ight, and consequently the electrical response record, was 

 the lower of the two. The vertical movement of the spot of 



ight which records the mechanical response is to be under- 

 stood as converted into horizontal by reflection from a 

 second mirror suitably inclined. This experimental arrange- 

 ment is similar to that employed for simultaneous mechanical 

 d electrical records in the case of Mimosa, as shown in 



r. 12. 



The record given in fig. 144 exhibits the simultaneous 

 echanical and electrical responses thus obtained. It will 

 seen that the minor electrical wave took place while the 

 flet was moving up from (a) and coming to its highest 

 ition at (ft). This was followed by a wave of higher 

 mplitude but shorter period, which coincided with the 

 movement of the leaflet again from its highest to its lowest 

 positions. It will thus be seen that the subsidiary electrical 

 ave of small amplitude and relatively long period coincided 

 ith the slow up- movement of the leaflet, and that the 

 rincipal wave, characterised by large amplitude and short 

 period, corresponded with the quick down-movement of the 



fiflet These galvanometric deflections indicated, it must be 

 iderstood, a condition of galvanometric negativity of the 

 ilvinule at the moments of its excitatory up and down 

 ovements. The following considerations make it easy to 



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