405 



takes place, when the decrease of the residiie-refractionarj-stage 

 surpasses the increase of the periodical refractioiiary-stage. For, if 

 this takes place, the normal ventricle-rhythm continues after a 

 protracted pause, till b}' accumulation the duiation of the residue 

 i-efractory-stage causes again the falling away of a ventricle-systole, 

 and the normal ventricle-rhythm is resumed again. So groups of 

 ventricle-systoles come into existence, which become gradually 

 smaller and smaller, till in the end the halved ventricle-rhythm is 

 reached in this way. 



3. Spontaneous alternations between the halved ventricle-rhythm 



and the normal one occur frequently. The cause of these alternations 



lies in the fact that during the halved ventricle-rhythm the katabolic 



. /duration of the refract.stage of the ventricle 



index of the ventricle ^ z ~r-, r— , 



V^ duration of a ventricle-period 



decreases again by restoration, till it has become less than 7a- Then 



the normal ventricle-rhythm sets in again. In this twice as rapid 



ventricle-rhythm ^) the katabolic index of the ventricle increases 



again, and consecpiently the halved rhythm of the ventricle sets in 



again. So these alternations can repeat themselves again several times. 



4. By extra stimulation of the ventricle the halved ventricle- 

 rhythm can artificially be converted into the normal twice as rapid 

 rhythm by the addition of one little ventricle-systole. This proves, 

 that during the halved rhythm of the ventricle the sinus-impulses 

 that are not answered by the ventricle, did really reach this part 

 of the heart, but rebounded on the not yet irritable ventricle-muscle. 



The normal ventricle-rhythm can likewise be converted into the 

 halved one by extra-stimulation. The enlarged post-compensatory- 

 systole fixed then the ventricle in the halved rhythm. 



I attributed these and many other results, not mentioned here, to 

 the fact, that an important factor of the action of the heart, viz 

 the refractory stage had been modified under the influence of the 

 employed poisons. Its duration increased by veratrine and by 

 digitalis. These poisons had no further possible mysterious actions 

 for the results, mentioned above. 



• The following observations made with regard to not poisoned 

 frogs' hearts afforded an unmistakable affirmation of this fact. The 

 before mentioned sudden and gradual transition into the halved 

 ventricle-rhijthm occurs likewise in the not poisoned frog's heart, the 

 spontaneous alternations between the halved rhythm of the ventricle 

 and the normal one can also be stated. 



^) During the normal ventricle-rhythm the katabolic index of the ventricle is 

 equal to the relative duration of the refractory stage. 



