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normal rhythm. The pauses in the latter rhythm, however, are much 
shorter, so that after some time the refractory period, at a given 
moment, after a systole of the ventricle, no longer depends only 
upon the preceding systole; for on account of the insufficient restor- 
ation between the quick heart-periods the preceding systoles have 
also had influence upon it; the refractory period increases again in such 
a way, that once more a halving of the ventricle-rhythm takes place. 
T could also bring about this change artificially, by intervening exactly 
in the same manner, by which I could alter the balved rhythm. 
By an extra-stimulation during or a short time after the diastole I 
made an extra-systole; this was followed by a compensatory pause, 
after which the post-compensatory systole, as always, is enlarged 
and widened. The enlarged refractory period is the cause that the 
halved rhythm returns again, because the first-following auricle-systole 
takes now again place in this refractory period. I could consequently 
these variations of rhythm bring about discretionally when the 
ventricle-rhythm had been halved for some time. 
I practised a second method of variation of rbythm according to 
a quite different principle and with as certain a result. When the 
ventricle pulsated after the veratrine-poisoning in the halved rhythm, 
1 eould by refrigeration of the sinus venosus make the impulses, 
originating in the latter, reach the ventricle in a slower tempo. 
Thus every second auricle-systole moved over.the refractory period 
of the preceeding ventricle systole, and restoration of the original 
ventricle-rhythm was the result. As a transition I obtained then 
heart-bigeminy and trigeminy. Consequently we obtained here by 
refrigeration of the sinus venosis an increase of the frequency of 
the ventricle. this is an exception to GaskELI’s experiment which 
teaches us, that refrigeration causes a decrease of the rhythm. Cale- 
faction of the sinus venosus causes, after the preceding experiment, 
a return of the rhythm to the halved one. 
Another method of bringing about variations of rhythm is cale- 
faction and refrigeration of the ventricle. Calefaction of the ventricle 
shortens the refractory period, and changes consequently the halved 
rhythm into the normal one; refrigeration of the ventricle causes 
then again a restoration of the halved rhythm. I could most quickly 
change the halved rhythm of the ventricle into the normal one by 
refrigerating the sinus venosis, and at the same time calefying the 
ventricle. Especially by this latter method the variation of the rhythm 
sueceeds always. The variation by an induction-stroke succeeds only, 
when the halved rythm has not yet existed a long time, or when 
at the reaction of the poisoning, the halved rhythm was to change 
