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bigeminus-groups. During this halved rhythm the total refractory 
period is thus of a longer duration than during each first systole 
of the bigeminus-groups. At the end of the diastole of the 4" curve 
in this halved rhythm I effect an extra-systole by an extra-stimulation 
(vide fig. 3 at Q). This extra-systole is followed by a normal 
Fig. 3. 
systole, but the then following impulse of the auricle, when reaching 
the ventricle, is not answered by the latter. 
The then following impulse occasions, it is true, again a ventricle- 
systole, but this systole is a little smaller and of shorter duration 
than the preceding systoles of the halved rhythm. The following 
auricle-curve descends a little deeper down from the top of the first 
systoles of the bigeminus-groups that are now following, than with 
the systoles of the halved rhythm. Consequently we have shortened 
the total refractory period of this ventricle-systole, compared with 
the duration of the refractory-periods of the halved rhythm. The 
consequence of this is that still another systole can follow, after 
which one ventricle-systole falls out, so that bigeminus-groups appear, 
among which occurs accidentally a trigeminus-group. If 1 had applied 
the extra-stimulation earlier in the diastole, the normal rhythm 
would have appeared. The extra-systole would then, proportionally 
to the greater diminution of the preceding interval, have been 
smaller, so that just as in fig. 1 the normal rhythm would have 
followed. This appears distinetly, if during the 6" group after the 
last of fig. 3 (vide fig. 4) | apply an extra-stimulation at an earlier 
Vig. 4. 
period of the diastole of the first curves of the bigeminus-group 
(at f). The extra-systole is then small, and the normal rhythm is 
restored, continues during 15 systoles, and changes then into some 
bigeminus-groups and afterwards into the halved rhythm. 
