541 
be covered by the excitation, owing to the fact that the stimulating 
electrode is placed close to the auriculoventricular groove '). 
Whereas after the stimulus applied at 1, the ventricle responds 
to the excitation by a single ventricular systole, the result is quite 
different after the stimulus administered at 2. This finds an expla- 
nation in the fact that here the induction shock affects the auricles 
a little earlier. Whereas at 1 the stimulus affects the auricles a little 
after the summit of the 7-deflection, at 2 it reaches the auricles 
a little before the summit of the 7-deflection. After an interval of 
*/, sec. the ventricle does not now respond to the excitation by a 
single systole, but by a series of five connected systoles. From the 
electrogram-curves it can be seen that between the various electro- 
grams the string does not remain in the position of rest or does so 
only for a short time. This “Häufung” of extrasystoles is due to 
the fact that the excitation reaches the ventricle somewhat sooner after 
the preceding ventricular systole than the preceding time. Now when 
looking more closely at the electrograms of the ‘‘gehaufte” ventri- 
cular systoles, it appears that they are all different (the 2.4 and the 
4th curve are most likely produced by partial systoles?)). We 
conclude, therefore, that the ventricle of the bled frog’s heart can 
respond after an artificial auricular extra-systole to the applied 
- excitation by a “Häufung” of extra-systoles, if only this excitation 
is applied early enough. An excitation that reaches the ventricle at 
a later moment produces a single premature ventricular systole. 
From the Pathological Laboratory of the 
April 1920. Amsterdam University. 
1) The deflection of the signal downwards is caused by a closure of the primary 
circuit; these closure shocks are turned aside, so that the ventricular systole, the 
electrogram of which commences somewhat later, cannot be engendered by this 
closure. The electrogram succeeds the preceding one after an interval of 101/, 
time units, so that it is retarded 1°’; time units, in consequence of the brief pre- 
ceding interval after the previons ventricular systole. 
So the ventricle pulsates in this registration in the halved rhythm, except that 
a bigeminal group has manifested itself here. After the two shocks this halved 
ventricular rhythm is disturbed artificially. 
2) It might also be supposed that the ventricle had been directly stimulated by 
current loops. However */; sec. is much too long for an electric latent time. So 
this supposition must be precluded. 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
