THE EROG-, AND ON THE ACTION OE THE VAGUS NERVE. 
1023 
the auricles, if it has previously been beating with half-rhythm, and increases the 
strength of the contractions both of auricles and ventricle. Also as long as the auricles 
are beating, the ventricle beats synchronously with them. From these facts I conclude 
that atropin slows the rate of the discharges from the motor ganglia without making 
them weaker; with the slower rate the impulses are therefore stronger than before, 
and the contractions must also be stronger, up to a certain extent of slowing, because 
with a certain slow rate of rhythm the maximum contractions of the heart are obtained. 
Whether the strength of the impulses is absolutely increased apart from the presumably 
beneficial effects of the slower rate I cannot say positively, though I am inclined to 
think they may be, as in some cases it has seemed to me that after atropin has been 
given it is necessary to screw the clamp up tighter than usual in order to cause the 
ventricle to remain quiescent. 
Muscarin applied to the auricles and sinus only, slows the rhythm both of auricles 
and ventricle, weakens the auricular contractions, and may cause the ventricle to beat 
with half-rhythm or to remain quiescent, before the auricular contractions have ceased. 
This shows that muscarin not only slows the rate of the discharges from the motor 
ganglia but also weakens the strength of the impulses. 
Curare applied to the auricles and sinus only, produces at first hardly any effect; it 
soon, however, slows the rhythm and may ultimately cause the ventricle to beat with 
half-rhythm. It therefore slows the rate of discharges from the motor ganglia and 
ultimately weakens the strength of the impulses. 
If the heart be suspended with the cut-open ventricle downwards and muscarin be 
applied to the ventricle alone, then the ventricular beats are weakened without altering 
the rhythm, as in Plate 70, fig. 26, curve A. If the preparation be now turned over 
without loosening the clamp, so that the auricles are downwards, atropin can be applied to 
the auricles and sinus alone without any chance of its reaching the ventricle. Then, as is 
seen in Plate 70, fig. 26, curve B, where the atropin was applied to the auricles and sinus 
at the point denoted by the arrow, the rhythm both of auricles and ventricle is slowed, 
and in consequence the ventricular as well as the auricular contractions are slightly 
strengthened in force. If, now, atropin be applied to the ventricle, the ventricular 
contractions immediately increase very greatly in strength, as is shown in Plate 70, 
fig. 26, curve C, which is the direct continuation of the curve B. This shows that 
atropin removes the weakening effect of muscarin on the muscular tissue itself. 
Again, if the heart be beating slowly in consequence of the application, of muscarin 
to the sinus and auricles alone, then atropin applied to the tissue on the same side of 
the clamp does not quicken the rate of rhythm, although it may cause the auricular 
beats to become stronger. Atropin, however, may undoubtedly cause the heart to 
beat again when it has ceased beating from the application of muscarin. 
We are now in a position to consider the effects of these three poisons upon the action 
of the vagus nerve, and I will take first the case of atropin upon the whole heart. 
Atropin when applied to the whole heart ultimately removes all the different effects 
MDCCCLX XXII. 6 P 
