CHAPTER VIIL 
ARTIFICIAL RHYTHM. 
Ir the umbrella of Aurelia aurita has becn 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 different 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 subsequent tracings I obtained by the 
method already described. 
