1589 
as I described already previously, and irritated by means of opening- 
induction strokes (movement of the signal upward) whilst the closing 
strokes were blended. 
Every frog’s heart was examined before the injection of veratrine 
by extra-stimulation, whilst after the poisoning this method was 
continued for a few hours. The number of experiments made in 
this way amounts to more than 200. 
|L. Eextra-stimulation of the heartpoint. 
I succeeded in bringing about artificially by extra-stimulations 
the modifications of rhythm, occurring spontaneously, previously 
described by me. As in these transitions the duration of the refract- 
ory-period plays an important part, it is of importance to know 
how it behaves after the poisoning. A great number of experiments 
made in this respect have taught, that its duration increases after 
poisoning with veratrine. I found even, at a certain stage of the 
poisoning before the halving of the ventricle-rhythm began, this 
ventricle refractory till far in the pause. After the halving the ven- 
tricle-muscle was then irritable again already during the diastole. 
This fact can only be explained, if we admit 2 components of the 
refractory stage after the poisoning. 
1. The periodical refractory-stage i.e. that part that is contributed 
during a special heart-period by the contraction of the ventricle- 
muscle during this heart-period. 
2. The residue refractory-stage; this second component is caused 
by the fact that, at the beginning of each systole, the heart-muscle 
is not entirely restored. 
The farther the poisoning advances, the more this 2"d component 
increases, till the halving of the ventricle-rhythm is completed. The 
latter occurs as soon as: 
the duration of the refractory-stage 
— surpasses 1. 
the duration of a sinus-period 
I called this the relative duration of the refractory-stage. 
As soon as the relative duration of the refractory stage is about 1, 
I can discretionatly modify the rhythm of the ventricle by an extra- 
stimulation. Every modification of rhythm that can occur spontane- 
ously, can also be obtained by means of an extra-stimulation. 
As an example of my material of curves the following experiment 
may serve. 
On the 30% of Aug. 1915 (curvesheet 60) I suspended a frog’s 
apex ventriculi in the way I described already. First I noted down 
about 100 systoles of the unpoisoned heart. By extra-stimulation of the 
102* 
