ARTIFICIAL RHYTHM. 179 
Any such merely mechanical source of fallacy 
being thus, I think, excluded, we are compelled to 
regard the facts of artificial rhythm as of a purely 
physiological kind. The question, therefcre, as to 
the explanation of these facts becomes one of the 
highest interest, and the hypothesis which I have 
framed to answer it is as follows. Every time the 
tissue contracts it must as a consequence suffer a 
certain amount of exhaustion, and therefore must 
become slightly less sensitive to stimulation than 
it was before. After a time, however, the ex- 
haustion will pass away, and the original degree 
of sensitiveness will thereupon return. Now, the 
intensity of faradaic stimulation which is alone 
capable of producing rhythmic response, is either 
minimal or but slightly more than minimal in 
relation to the sensitiveness of the tissue when 
fresh; consequently, when this sensitiveness is 
somewhat lowered by temporary exhaustion, the 
intensity of the stimulation becomes somewhat less 
than minimal in relafion to this lower degree of 
sensitiveness. The tissue, therefore, fails to perceive 
the presence of the stimulus, and consequently fails 
to respond. But so soon as the exhaustion is com- 
pletely recovered from, so soon will the tissue again 
perceive the presence of the stimulus; it will there- 
fore again respond, again become temporarily ex- 
. hausted, again fail to perceive the presence of the 
stimulus, and again become temporarily quiescent. 
Now it is obvious that if this process occurs once, 
it may occur an indefinite number of times; and 
as the conditions of nutrition, as well as those of 
