342 



COMPARATIVE ELECTRO-PHYSIOLOGY 



In taking up this investigation on the pitcher of Nepenthe 

 it appeared to me that much light would be thrown, by the 

 study of this simple organ, on the many- difficulties connected 

 with the response of the more complex digestive organs of 

 the animal. This surmise has proved to be fully justified, 

 for in the experiments which I have carried out in the latter 

 field, the results are a mere repetition of these typical effects 

 seen in Nepenthe under corresponding circumstances. 



Before passing from 

 Nepenthe to the study 

 of digestive tissues in 

 animals, it will be well 

 to deal here with the 

 more complex type of 

 vegetal digestive organ 

 seen in the plant 

 Drosera. I took for my 

 experiment a specimen 

 of the Indian Drosera 

 longifolia, the upper 

 surfaces of whose leaves 

 are covered, as is well 

 known, with glandular 



tentacles. Here, as in 

 the case of the pitcher 



FiG. 208. Photographic Record of Responses 

 in Fresh Leaf of Drosera to Equi-alternating 

 Electrical Shocks 



The first series show normal responses. Current _ 7 , 



from upper glandular to lower non-glandular Of Nepenthe, the re- 

 surface. In the second series normal response sponse of leaves which 

 is reversed to positive, after tetanisation, T. 



are fresh and have not 



been subjected to previous excitation, is by induced negativity 

 of the glandular surface, and this is reversed to positive under 

 long-continued stimulation. These two phases are seen in 

 figure 208, in which the first series is a record of normal 

 responses of galvanometric negativity, to equi-alternating 

 shocks applied at intervals of one minute ; and the second, 

 the reversed responses exhibited by the same leaf, to the 

 same stimulus, when it has, in the meantime, been subjected 

 to tetanising shocks for three minutes continuously. It is 



