ARTIFICIAL RHYTHM. 199 



posing a large and sometimes a small portion of the 

 tissue to the influence of the irritant. As I in- 

 variably obtained the same result, there can be no 

 doubt that in the case of chemical stimulation the 

 artificial rhythm depends for its manifestation on 

 the presence of a constant stimulus, and is not 

 merely some kind of obscure fluttering motion 

 which, having been started by a stimulus, is after- 

 wards kept up independently of any stimulus. 



Such being the case, I naturally expected that if 

 I were to supply a constant stimulus of a thermal 

 kind, I should also obtain the phenomena of arti- 

 ficial rhythm. In this, however, my expectations 

 have not been realized. With no species of Medusa 

 have I been able to obtain the slightest indication 

 of artificial rhythm by immersing the paralyzed 

 animals in heated water. I can only explain this 

 fact by supposing that the stimulus which is sup- 

 plied by the heated medium is of too uniform a 

 character over the whole extent of the excitable 

 tissues; it would seem that in order to produce 

 artificial rhythm there must be a differential in- 

 tensity of stimulation in difTerent parts of the 

 responding tissue, for no doubt even the excitatory 

 influence of acidulated water is not of nearly so 

 uniform an intensity over the whole of the tissue- 

 area as is tbat of heated w^ater. 



In now quitting the subject of artificial rhythm 

 as it is manifested by the paralyzed bell of Sarsia, 

 it is desirable again to observe that sustained 

 artificial rhythm cannot be produced by means of 

 chemical irritation in the case of any one of the 



