CHAPTER VIII. 



ARTIFICIAL RHYTHM. 



If the umbrella of Aurelia aurita has been para- 

 lyzed by the removal of its lithocysts, and if it is 

 then subjected to faradaic stimulation of minimal 

 intensity, the response which it gives is not tetanic, 

 but rhythmic. The rate of this artificial rhythm 

 varies in different specimens, but the limits of 

 variation are always within those which are ob- 

 served by the natural rhythm of diff*erent specimens. 

 The artificial rhythm is not in every case strictly 

 regular; but by carefully adjusting the strength of 

 the current, and by shifting the electrodes from one 

 part of the tissue to another until the most appro- 

 priate part is ascertained, the artificial rhythm 

 admits in most cases of being rendered tolerably 

 regular, and in many cases as strictly regular as is 

 the natural rhythm of the animal. To show this, 

 I append a tracing of the artificial rhythm (Fig. 

 25), which may be taken as a fair sample of the 

 most perfect regularity that can be obtained by 

 minimal faradaic stimulation.* 



* This and all the subscqujut tracings I obtained by the 

 method already described. 



