1032 
fa mm. 
Fig. 1. 
the ventricle continuing to pulsate when undisturbed, would not 
have passed into systole. Therefore this extra-systole is followed by 
a compensatory pause. When at 3 and 4 I repeat the same expe- 
riment, but apply now at 4 the 2°¢ extra-systole with a slight scope 
at a moment, when in normal circumstances the ventricle would 
likewise have produced a systole, an extrasystole occurs that is not 
followed by a compensatory pause. As before the injection with 
digitalis a slighter stimulation on the basis of the ventricle in the 
beginning of the diastole promptly caused an extra-systole of the 
ventricle, this fact proves clearly the decrease of the irritability of 
the muscle of the ventricle. At the same time this experiment 
teaches us, that an extra-systole of the ventricle is only followed 
by a compensatory pause, when the extra-systole falls entirely beyond 
the physiological period of stimulation. 
In different ways the first stage can pass into the 2°¢. As a rule 
the rhythm of the normal equally high systoles passes into alterna- 
tion. The large systole of an alternation-pair is then greater, the 
little one smaller than the systoles of the normal rhythm. In Fig. 2 
such a transition is represented. Fig. 3 shows an alternation, in 
which the little systole sets in retardedly, on account of a distinct 
prolongation of the a—v interval. This causes the distance between 
the beginning of a great ventricle-systole and the beginning of the 
next following little ventricle-systole to become considerably greater 
than the distance between a little systole of the ventricle and the 
next following great one. 
Now the alternation lasts very short, now longer, and passes then 
into halving of the rhythm of the ventricle. It occurs likewise that 
the alternation does not set in at all, so that then the normal rhythm 
of the ventricle passes directly into the halved rhythm or into formation 
of groups, as I described circumstantially after poisoning with veratrine. 
2. Second stage. Consequently the 2d stage begins usually with 
