336 



COMPARATIVE ELECTRO-PHYSIOLOGY 



we are already familiar, as the invariable accompaniment of a 



positive turgidity-variation. 



Thus, if galvanometric negativity is to be taken as the 



concomitant of the expulsion or secretion of fluid, it would 



appear that the opposite 

 process of absorption would 

 be indicated by the respon- 

 sive galvanometric posi- 

 tivity. 



Again the fresh pul- 

 vinus of Mimosa responds, 

 when excited, by a me- 

 chanical fall, a negative 



FIG. 201. Glandular Surface of a Portion 

 of the Living Membrane of the Pitcher 

 of Nepenthe. 



turgidity-variation, and by 

 galvanometric negativity. 

 But after long-continued 

 stimulation, these normal responses are found to undergo 

 reversal. The pulvinus expands; water must be re-absorbed, 

 and the leaf is re-erected. The normal galvanometric nega- 

 tivity is now reversed to positivity. It will thus be seen that 

 while, in a fresh tissue, stimulus gives rise to expulsion of 

 (4) fluid the electrical indi- 



cation of this process 

 being galvanometric nega- 

 tivity in a tissue which 

 has already, on the other 

 hand, been under con- 

 tinuous stimulation there 

 will be a tendency towards 

 the phasic reversal of re- 

 sponse to galvanometric 

 positivity, indicative of the 

 process of absorption. 

 In the case of motile 



53 



* 



FIG. 202. Transverse Section of Tissue of 

 Pitcher of Nepenthe. 



u, outer surface ; L, inner surface ; g, glands 

 present in the internal surface. 



tissues, these excitatory 

 reactions of the outflow and inflow of fluids appear to us of 

 little consequence, except in the form of those appropriate 



