and Plants to the Electrical Phenomena associated with it. 55 



diagram 2 indicates that the conditions correspond with those which 

 are there theoretically represented. During each period of excitation 

 (tetanus) the movement upwards of the meniscus is determined by the 

 difference of potential. During the intervals it follows in its fall the 

 similar curve of depolarisation. 



Photograph 7.* 



From this we may now proceed to other forms of experimenta 

 tetanus in which the excitations are less frequent. Provided that the 

 frequency is not much less than 40 per second, the general contour of 

 the curve resembles the other one, with the exception that the effect. of 

 each excitation is seen separately (Photo. 8). If the frequency is 

 diminished to 20 per second the undulations are more ample, while the 



Photograph 8.f 



curve rises to a lower level, the reason obviously being that the electro- 

 meter is acted on by a smaller number of excitations in a given time. 



* Frequency of excitation as in Photo. 6. The original shows similar undulation* 

 in the ascents, which the copy by inadvertence does not show, 

 t The first four undulations have been imperfectly copied. 



