9 8 



COMPARATIVE ELECTRO-PHYSIOLOGY 



about. Now we have seen that the diminution of normal 

 response may be brought about by the augmentation of the 

 internal factor, tending to enhance the force of restitution, 



and the necessary augmentation of 

 the internal factor may be the result 

 of an increase of internal energy. 

 Thus while the plant is the recipient 

 of a continuous income, its responsive 

 expression is alternately one of emis- 

 sion and absorption of energy. Thus 

 negative and positive succeed each 

 other or vice versa. Such a phasic 

 alternation is widely present, as we 

 shall see, in the response, not only 

 of various living tissues, but also of 

 inorganic substances. The follow- 

 ing record (fig. 67) exhibits this oscillatory response in arsenic 

 under the continuous stimulation of electric radiation. In 

 the case of Mimosa, under continuous stimulation, we obtain 



FIG. 67. Oscillatory Re- 

 sponse of Arsenic acted 

 on Continuously by 

 Hertzian Radiation 



Taken by method of con- 

 ductivity variation. 



FIG. 68. Alternate Fatigue (a) in Electrical Responses of Petiole of 

 Cauliflower ; (b) in Multiple Electric Responses of Peduncle of 

 /> io/i/i vtum ; (r) in Multiple Mechanical Responses of Leaflet of Bio- 

 phytiini ; and (d) in Autonomous Responses of Desmodiitm 



a single alternation, and a certain period must then elapse, 

 before the response can be repeated. In other cases, how- 

 ever, continuous stimulation may give rise to two, or three, or 

 a large number of similar alternations. 



