546 
of two excitations, passing through the two chambers in opposite 
direction. The excitations clash against each other and are annibi- 
lated. Now we understand that the auricular systole succeeding the 
extra stimulus, originates partly under the influence of the periodic 
Fig. 3. 
\ 
sinus impulse and partly from the extra stimulus.') It is also clear 
that this auricular systole cannot in this case be followed by a 
ventricular systole. In the lower curves, registered a little later, 
this experiment is repeated with the same result at the first and 
the third upward deflection of the signal. At the second upward 
deflection of the signal the stimulus is given a little later, so that 
then an extrasystole of the ventricle appears. In fig. 4 are illustrated 
the suspensioncurves and the electrograms of a frog’s heart after 
antiavin poisoning. Initially the ventricle pulsated in halved rhythm, 
which at the first upward deflection of the signal was changed into 
the normal rhythm of twice the velocity. At the second upward 
deflection of the signal another inductionshock is administered in 
the auriculo-ventricular groove.?) We see from the stringcurve that 
this stimulus is administered a short time after the P-deflection. At 
this moment the ventricle is apparently still refractory, so that an 
') It goes without saying that it depends on the moment, at which the extra- 
stimulus is administered to which impulse the greater part of the auricular systole 
owes its origin. So, for instance, in Fig. 6 the two auricular systoles will arise 
for the greater part from the extra stimulus. 
*) The moment at which the extra stimulus is applied, is marked by the signal 
and may also be seen_from the stringcurve, which shows a small gap owing to 
a short swerving of the string. 
