1144 
again. The duration of 3 periods of this halved stage is equal to 
the duration of 2 bigeminus-groups. The distance between 2 auricles 
in one group is 2 sec., the duration from the 2rd to the first of the 
following group is 2'/, sec. This teaches us how great the retardation 
can be in the connection-systems between the sinus venosus and the 
auricle. 
P-bigeminus does not only occur as transition with halving of 
rhythm, but likewise as transition between the halved rhythm and 
a still slower rhythm. 
Fig. 7 is an example of this phenomenon.-The upper-row gives 
the curves before the injection. The 2™¢ row of curves is represented 
10 min. after the injection of 10 drops of veratrine into the abdo- 
minal cavity. In the 8° row (represented 5 min. after the 2rd) the 
rhythm is halved. The same stage exists still in the 4 row, but 
the systoles have become smaller, the «-v-interval has increased a 
second time (in the halved rhythm of row 3 the lengthened a-v- 
interval was reduced again). In the 5th row the systoles are ranged 
in bigeminus-groups. Measurement shows us that from the normal 
rhythm after the first systole of each group one systole, after the 
Jud systole 2 systoles, are missing. 
Here we have consequently a bigeminus of which alternately 
every 3° and every 2"¢ systole are expressed. This bigeminus also 
is again a transition into a slower rhythm. The last 2 systoles of tiis 
row indicate this rhythm. Here every 3 systole is every time 
expressed. 
With unpoisoned frog’s hearts heart-bigeminy occurs also frequently 
as transition with halving and variation of rhythm. Thus T have a 
series of curves of a suspended normal frog’s heart, on which first 
groups of 8, 10, 4, and 3 were formed; afterwards bigeminy took 
place, which was converted into the halved rhythm. 
Fig. 8. 
Bigeminus-groups — halved rhythm — bigeminus-groups. 
This halved rhythm was afterwards converted again into heart- 
bigeminy. These last 2 transitions are represented in Fig. 8. Two 
of the bigeminus-groups answer to 3 systoles of the halved rhythm. 
