696 COMPARATIVE ELECTRO-PHYSIOLOGY 



explains the peculiar electrical responses of Desmodium 

 gyrans, which are concomitant with the autonomous 

 mechanical pulsations of the leaflet. I find that, corre- 

 sponding with one complete mechanical pulsation, there are 

 two electrical pulses. Of these the principal electrical wave 

 coincides with the down-movement of the leaflet, and the 

 smaller with the up. The electro-motive intensity of the 

 principal wave is nearly 1-5 times that of the subsidiary. 

 In a particular experiment, for example, while the value of 

 the former was -0024 volt, that of the latter was -0016 volt. 

 These electro-motive variations are expressions of funda- 

 mental excitatory effects, and not dependent on the 

 mechanical movement of the leaflets. For when the 

 responding leaflet is physically restrained, the electro-motive 

 responses exhibit even greater intensity than before. This 

 will be seen in the simultaneous records of mechanical and 

 electrical pulsations given in fig. 145. 



An important subject of inquiry lay in the accurate 

 determination of the death-point. This investigation afforded 

 striking demonstration of the fact that it is a single 

 excitatory reaction which is expressed in different ways 

 under different modes of record. It has been shown that 

 when the experimental tissue is subjected to a gradual rise 

 of temperature, there is a definite point at which an 

 excitatory spasm occurs, marking the initiation of death. 

 If a continuous record be taken of the concomitant variation 

 of length, increasing expansion is found to be converted at 

 this point into a sudden contraction. In an anisotropic 



I organ like the pulvinus of Mimosa the erectile movement of 

 the leaf is abruptly transformed into one of fall. A curled 

 tendril exhibits at this point a sudden uncurling. Taking, 

 again, the electro-motive method of record for the detection 

 of the death-point, the increasing positivity of the 

 specimen is spasmodically reversed to negativity. Finally, 

 on employing for the record the method of resistivity 

 variation the increasing is seen to become suddenly 

 changed into a diminishing resistance. It is found, how- 



