1024 
Dft. W. H. GASKELL OH THE RHYTHM OF THE HEART OF 
of vagus stimulation, it prevents any diminution of the force of the contractions, and 
d fortiori any standstill, it prevents any increase of the contraction force and it 
prevents any acceleration. Examination of the various atropin curves which I possess 
shows that the first effect of atropin is to lessen the extent of the diminution of the 
force of the contractions caused by the stimulation of the nerve, so that in this stage 
the vagus finally produces acceleration''* and augmentation of the beats only. In the 
further stage with the slow vigorous contractions characteristic of the atropinized 
heart, less and less acceleration and less and less augmentation of the force of the 
beats occurs, until at last stimulation of the nerve, even with the strongest current, 
is absolutely ineffective. 
This experiment not only proves that atropin prevents the action of the vagus, but it also does away 
with an objection that might by some possibility be made against such results of vagus stimulation as I 
have recorded, viz.: that they are due, in part at all events, to escape of current, an objection which I 
believe has already been urged against ScJHELSKE’sf assertion that in certain cases where the heart was 
not beating, he was able to make it beat again by stimulation of the vagus. I have, however, satisfied 
myself, apart from the action of atropin, that the effects seen are due to the vagus stimulation alone, and. 
not to any escape of current. Thus the space between the electrodes and the tissue is considerable, and 
great care Was always taken that there should be no communication between the electrodes and the heart 
except by means of the bare nerve. Again, if the thread to which the nerve is attached be first well 
moistened and then placed on the electrodes instead of the nerve, no effect whatever is produced upon 
sending the current through, although upon gently drawing the nerve on the electrodes which have 
throughout remained in the same position, the characteristic effect is immediately produced on stimulation. 
Also if the electrodes be placed directly upon the tissue between the heart and the forceps which hold the 
oesophagus, no effect whatever is produced on the heart with a current of the same strength as is sufficient 
to cause all the effects which are seen when the nerve is stimulated. 
Since the vagus acts both upon the motor ganglion and the muscular tissue, and 
atropin is able to remove the whole effect of the action of the nerve, it naturally 
follows that by the local action of poisons it may be possible to abolish the vagus action 
in one part of the heart while leaving it intact in another. With this view I have 
applied the poisons either to the ventricle alone or to the sinus and auricles alone, and 
have obtained certain somewhat striking results; at the same time the number of 
these experiments is hardly sufficient as yet to allow me to say that these results are 
in every case so constant as to be entirely due to the action of the poison upon the 
sinus and auricles in one case or the ventricle in the other. 
Thus, for instance, in Plate 70, fig. 27, muscarin had been applied to the sinus and auricles only, until, 
as is seen, the auricular beats had become slow, irregular, and somewhat weaker. The vagus was stimulated 
between the two vertical lines, and, as the figure shows, no effect was produced either on the rhythm or 
on the force of the auricular contractions (although previous to application of the muscarin the auricular 
contractions were augmented in force by the nerve stimulation); while on the other hand the ventricular 
contractions were increased in force to as great an extent as at the beginning of the experiment. Also the 
* Schiff, Molesch. Unters., 1865, S. 58. 
j- Ueber die Yeranderungen der Erregbarkeit durch d. Warme, S. 20. Heidelberg, 1860, 
