Physiology. — ''On the transmission of stimula through the ventricle 

 of frogs hearts''. By Dr. S. de Boer. (Commnnicated by Prof. 



VAN RuNBEHK). 



(Communicated in the meeting of June 30, 1917). 



The following facts were among others stated by me in the phar- 

 rnacophysiological investigations I made into frogs' hearts, after 

 1 had poisoned them with veratrine or digitalis. 



1. The duration of the refractory stage of the ventricle-muscle 

 increases after the administration of each of the two poisons, and 

 so does likewise the a-i;-interval ; at last the contractility of the 

 ventricle-muscle decreases. 



2. As soon as the relative duration of the refractory-stage 



duration of the total refract, stage^ , , ^ . , , 



-T T" — ^ : r— i surpasses the value 1, suddenly 



duration of a smusperiod / 



or gradually the normal ventricle-rhythm changes into the halved one. 



a. The sudden halving of the ventricle-rhythm comes about in 

 the following manner: 



The duration of the refractory -stage of the ventricle has increased 

 during the normal rhythm of the ventricle for this reason that the 

 ventricle-muscle was not yet entirely restored at the beginning of 

 every ventricle-systole. What was still wanting to this restoration, 

 was called by me the residue refractory stage. 



The periodical refractory-stage was added to it by every systole, 

 80 that the total refractory-stage consists of two components. If now 

 the relative duration of the refractory-stage has become longer than 

 1, the next following ventricle-systole falls away, and a protracted 

 ventricle-pause is the consequence. This protracted pause influences 

 the two components in an opposite sense. 



The ventricle-muscle restores itself better, so that the residue- 

 refractory -stage decreases. But after a protracted pause the next 

 following systole of the ventricle is considerably enlarged, consequently 

 the duration of the periodical refractory-stage of the ventricle increases. 

 If now this increase of the duration of the periodical refractory- 

 stage surpasses the decrease of the residue-refractory stage, then 

 suddenly halving of the ventricle-rhythm sets in. 



h. The gradual transition to the halved ventricle-rhythm however 



