136 STUDIES IN ELECTRO-PHYSIOLOGY: 



its maximum, another diametrically opposite to it is at its 

 minimum. The phases of maximum and minimum tur- 

 gidity thus pass rhythmically round the organ, and the 

 apex is consequently compelled to describe a spiral line as 

 it grows. ... It is not infrequent for the rhythmic change 

 in the turgescence to affect only two sides ... its changes 

 will thus resemble, those of a flattened organ which can 

 only be made to oscillate backwards and forwards." 



Until I read Green's Vegetable Physiology I was not 

 aware that this rhythmicality of movement had been 

 observed, but the subject is to me one of peculiar interest. 

 It so happens. that some years ago I carried out a series of 

 galvanometric tests with plants invariably at night 

 and took note of phenomena which, in their electrical 

 aspect, were suggestive of rhythmic inspiration and 

 respiration.' 



The paralysis or destruction of protoplasmic movement 

 in both animal and vegetable bodies appears to occur from 

 identical causes, as will be seen on reference to the Study 

 of Amoeboid Movement. 



One question which has engaged my attention is : 

 Can there be any analogy between the propagation of 

 impulse in mammal and plant ? Though the possession of 

 nerves is denied to the latter by some authorities, there is 

 little if any doubt that they are present in a rudimentary 

 form, and in such case the propagation of stimuli should, 

 logically, be possible. 



Green remarks : "In considering broadly the result 

 of stimulation " (of plants) " we must notice at the outset 

 that it provokes a purposeful response. The living 

 substance appears to have a definite aim." 



" If any one of the small leaflets of a leaf, on a shoot of 

 Mimosa with five or six leaves, is stimulated by means of 

 the hot focus of a burning glass, all the other leaflets of the 

 same leaf gradually fold together, and after a time the 



