THE FEOG, AND ON THE ACTION OE THE VAGUS NEEVE. 
1025 
fact that the ventricular rhythm was throughout the same as the auricular shows that the muscarin had 
caused the slowness and irregularity of the rhythm by its action upon the motor ganglia, and not because 
it had rendered the auricular muscle unable to respond to every impulse. The curve affords, too, a good 
proof that separate and not continuous impulses pass from the ganglia to the ventricle, otherwise it is 
impossible to conceive that with the increased excitability of the muscle caused by the vagus action it 
would be obliged to contract in the same slow irregular manner as the auricles. 
Very soon after this curve was taken the muscarin caused the action of the motor ganglia to cease 
altogether, and then it was found that stimulation of the vagus was unable to make either ventricle or 
auricle beat. 
This shows that the vagus is not a motor nerve to the muscle, for if it were so 
it must have caused contractions of the ventricle, seeing how powerfully it had been 
able to affect the ventricle a very short time before. 
Again, cases occur where the curves show that muscarin applied to the auricular side only had very 
greatly reduced the size of the auricular beats, somewhat slowed the rhythm, and by its weakening action 
on the strength of the impulses caused the ventricle (which had previously been beating synchronously 
with the auricles) to remain quiescent. Stimulation of the nerve produced only a slight quickening of 
the auricular beats, and after the end of the stimulation a series of ventricular beats similar to what has 
already been described when the ventricles were reduced to standstill either by clamping or heating the 
auricles and sinus. 
Muscarin, then, is apparently able to prevent the action of the vagus upon the 
auricles when applied to the auricles and sinus alone, without thereby preventing the 
action of the nerve upon the ventricle. 
When atropin is applied to the sinus and auricles alone, then, simultaneously with 
the appearance of the slow vigorous beats thereby caused, the action of the vagus both 
on the rate of rhythm and upon the force of the ventricular as well as the auricular 
contractions entirely disappears. In fact, atropin applied to the sinus and auricles 
alone is as effective as when applied to the whole heart. 
Curare applied to the auricles and sinus alone is able to prevent the action of the 
vagus nerve upon the auricular muscle, as far, at all events, as the diminution of the 
force of the contractions is concerned, without, as in the case of muscarin, greatly 
diminishing the force of the auricular contractions, while at the same time it leaves 
intact the action of the nerve upon the force of the ventricular contractions. 
When any one of these three poisons is applied to the ventricle alone, the action of 
the vagus upon the force of the ventricular contractions is gradually removed without 
affecting its action upon the rhythm of the heart or upon the force of the auricular 
contractions. The usual sequence of events is as follows :—Soon after the application 
of the poison the nerve stimulation is no longer able to cause any diminution of the 
force of the contractions of the ventricle, so that in this stage it causes simply an 
increase of force with acceleration, if the auricular beats are accelerated. The 
maximum of this increase is less, and takes place later after the stimulation than 
before the application of the poison. As the action of the poison continues, the 
ventricular beats become smaller and smaller, and the augmentation of their con¬ 
tractions due to the vagus stimulation becomes less and less marked, until at last the 
6 p 2 
