THE FROG, AND ON THE ACTION OF THE VAGUS NERVE. 
1007 
Tims if standstill is in variably due to a slowing of the rate of the discharges from 
the motor ganglia, experiment ought naturally to show that the beats which first occur 
after the standstill are more infrequent than before the nerve was stimulated, and that 
the subsequent recovery of the rhythm up to or beyond the original frequency takes 
place gradually and not abruptly. Also a stimulation which is unable to cause complete 
standstill ought to produce the effect nearest to standstill, viz.: a greater or less slowing 
of the heart independently of any alteration in the force of the contractions. 
If, on the other hand, standstill is invariably caused by the action of the nerve upon 
the muscular tissue, so that the latter does not respond to the impulses coming to it, 
then we should expect to find (in accordance with the law of Bowditch* that the force 
of the contractions of the ventricle is not dependent upon the strength of the stimulus) ; 
that the first beats which occur after the standstill are very small, that the force of the 
contractions gradually increases up to or beyond the orignal force, and that the rate of 
rhythm after the standstill is not necessarily slower than before the stimulation of the 
nerve. Also a stimulation which is unable to cause complete standstill ought to produce 
the effect nearest to standstill, viz.: a more or less marked diminution in the force of 
the contractions independently of any alteration of rhythm. 
The majority of physiologists have hitherto accepted the first of these views as the 
invariable explanation of the standstill of the heart caused by the action of the vagus 
nerve, and in accordance with this view always speak of the vagus as causing inhibition 
of the heart’s action. 
In this present paper I propose to give evidence that, at all events in the heart 
removed from the body, the second view is the true one, and in accordance therefore 
with this conception I have throughout spoken of the vagus as causing quiescence of 
the heart. 
It is of course possible and indeed probable that both these views may be true, 
and that therefore the vagus may cause standstill sometimes by the one action and 
sometimes by the other. Whether this is so or not I am not at present able to 
judge ; I can only say that in the suspended heart I have never as yet seen any 
reason to suppose that the vagus is capable of producing such a prolonged slowing 
of the rate of the discharges from the motor ganglia as to entitle that slowing to the 
name of standstill of the heart; while on the other hand the quiescence of the heart 
produced by the action of the nerve upon the force of the muscular contractions may 
last for a considerable time. 
Again, physiologists and pharmacologists have hitherto considered that the inhibitory 
action of the nerve is abolished when its stimulation no longer causes standstill or 
slowing of the heart. This view will clearly require modification if the quiescence of 
the heart is due to the action of the nerve upon the force of the contractions rather 
than upon the rate of the discharges from the motor ganglia. Indeed, it will be no 
* Ludwig’s Arlbeiten, 1871, S. 139. 
MHCCOLXXXII. 6 N 
