331 
These two factors contribute to the origin of “gehaufte” extrasystoles. 
The excitation-wave, it is true, bas not traversed the ventricle in stages, 
but the time required for a circuit, has nevertheless increased. The 
refractory stage being shortened, the excitation-wave performs again 
its circuit through the ventricle, because when it has arrived at the 
starting point, the ventricle has at that spot become excitable again 
after the shortened refractory stage. The second time the excitation-wave 
again traverses the ventricle slowly and again the contraction is of 
short duration. In this way the excitation-wave may move round the 
ventricle several times running and engender a series of reduced 
ventricular systoles. 
The electrograms imaging this process show the indicated character- 
istics of a slackened conduction of the excitation-wave '). After the first 
extrastimulus three “gehäufte” extrasystoles revealed themselves. 
During these three extra-systoles we see in the electrogram-curve 
one P-deflection (P;) preceding the next P by exactly one periodic 
interval. It would seem, then, that during these “gehäufte’” systoles 
of the ventricle the periodicity is not disturbed. At 2 the stimulus 
is repeated on the apex of the negative 7-deflection and again three 
“gehäufte” extrasystoles *) are generated. Now also the pulsations of 
the auricle are undisturbed. 
The curves of Fig. 2 are derived from the same frog’s heart. At 
1 an induction shock was applied to the base of the ventricle towards 
the close of the 7-deflection, which resulted in three “gehäufte” 
extra-systoles. At 2 the stimulus was renewed at the same time of 
the ventricular period, which produced a curve illustrating a ming- 
ling of irregular fibrillation and ‘“gehaufte’ extrasystoles. The 
first curve after the stimulus is a distinct extrasystole (as can be 
concluded from the deflections of the string, which show an &-deflection 
and an intense negative 7-deflection). Subsequently the electric curve 
becomes very irregular and at the close two distinct extrasystoles 
appear again, each with an R-and 7-deflection. When the ventricular 
base is stimulated again at 3, two extrasystoles are evolved. 
Fig. 3 shows the curves of another frog’s heart. 
The electrograms of the normal rhythmic ventricular systoles 
1) The influence of the rate of conduction upon the form of the ventricular 
electrogram is discussed by me extensively in Pfliiger’s Arch. Bd. 173, Seite 78, 
1918 and Arch. Néerl. de Physiologie, tome III (1918) p. 7. 
2) It will be seen that the duration of the pause after the ‘“‘gehiufte” extra. 
systoles is very different sometimes, as appears from the figures. The time of the 
post-undulatory pause may also be very different. I purpose to revert to these 
facts in a later communication. 
22 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
