324 
lower registration the suspension-curve is slightly interfered with by 
a momentary movement of the frog). Also through inspection I 
noticed that the auricles continued beating during the fibrillation. 
I also possess the registration of two more frog’s hearts that kept 
fibrillating after a stimulus. Here also the deflections of the string 
were initially irregular and here also they became more regular 
afterwards. In these registrations large and small deflections were 
alternating and the auricles continued beating regularly. 
Significance of the experimental results obtained for an 
explanation of ventricular fibrillation. 
Before accounting for ventricular fibrillation in a way different 
from all previous interpretations, [I will just summarize the main 
results of this investigation. It should be remembered that the ven- 
triele can only be made to fibrillate by an extra-stimulus if this 
stimulus is applied directly after the close of the refractory stage. 
Fibrillation never appears when the stimulus is given later with the 
same force and at the same spot; if it is, it will result in an ordi- 
nary extrasystole. 
To these facts I attach great value. So the ventricle will begin 
to fibrillate after an extra-stimulus only when its metabolic condition 
is bad. This condition is still bad at the beginning of the excitable 
period, because in so short an interval after the termination of the 
preceding systole the ventricular muscle has not been able to recover 
itself. From this bad metabolic condition of the ventricle it follows: 
1. That the contractility of the ventricular muscle is bad. After 
an extra-stimulus there is a brief small contraction. This brief extra- 
contraction is accompanied by a brief refractory stage. 
2. That the conduetivity of the excitation through the ventricle 
is slight. 
These two circumstances are conclusive for the origin of the deli- 
rium. These conditions are quite different when the stimulus is 
applied at a later period. Then the metabolic condition is much 
better, because after the preceding systole the ventricle has had 
more time for recovery. Consequently the contractility and the con- 
ductivity are much better; then the excitation passes rapidly through 
the ventricle and a properly co-ordinated extra-systole results from 
the stimulus. 
In order to fully understand the origin of the delirium, we must 
first consider the brief delirium, since in some of our experiments 
the delirium was only of very short duration and consisted of 2 or 
