157 



The lieart has served iis as a type of the (wo automaticilies; the 

 natural one depending on the radio-activitj of potassium, or rubidium, 

 and the artificial one, tliat can be evoked by the radio-activity of 

 uranium, thorium, ionium, radium, emanation. In quite the same 

 way there is a mutual resemblance between the alpha- and beta- 

 automaticities of the gut and the uterus. 



