1006 
DR. W. H. GASKELL ON THE RHYTHM OF THE HEART OF 
Another view, which largely depends for its support upon the action of various 
poisons, is, that the nerve does not produce standstill by direct interference witli the 
motor ganglia, but because it excites some inhibitory mechanism which is interpolated 
between these ganglia and the muscular tissue. Both these views have one hypothesis 
in common, viz.: that the inhibitory action of the nerve is due to the prevention of 
the discharges from the motor ganglia from reaching the muscular tissue, and not to 
the action of the nerve upon the muscle itself. In pharmacological literature especially 
this hypothesis has become so predominant that again and again the statement is 
made that such and such a poison paralyses or stimulates some part or other of the 
vagus nerve, when the facts only show in the first case that the vagus is no longer able 
to produce standstill, and in the second that the poison has by its action caused the 
heart to beat slower. 
Again, a number of observers, notably Schiff,* have asserted that stimulation of 
the vagus nerve of the Frog under certain circumstances always causes acceleration 
of the heart’s rhythm, and not slowing : a result which, conjoined with the action of 
atropia, has led to the supposition that the Frog’s vagus contains accelerator as well 
as inhibitory fibres, and a fresh set of hypotheses has been made with respect to the 
relative vitality of these two sets of fibres. 
Finally, it has been long known that the contractions which immediately follow the 
standstill caused by vagus stimulation are much weaker than the normal contractions, 
and NuELt has shown that stimulation of the nerve weakens, at all events the 
auricular contractions, even without a preliminary standstill. 
We have, therefore, according to present views at least, three sets of fibres in the 
Frog’s vagus, viz.: fibres which are capable of slowing or entirely preventing the dis¬ 
charges from the motor ganglia; fibres which accelerate those discharges; and fibres 
which in some way or other diminish the force of the cardiac contractions. In addition, 
we have various statements that sometimes only one vagus is active, that at certain 
times of the year the vagus loses all power, &c. 
The literature of the subject then affords ample evidence of considerable discrepancy 
not only as to the explanation of the action of the vagus, but also as to observed facts 
connected with that action. The reason of this confusion will appear in the following 
pages, and I will say at present that it is based upon a view of the nature of the 
action of the vagus, which appears to me to be too much one-sided. Too great promi¬ 
nence has hitherto been assigned to the action of the nerve upon the motor ganglia— 
too little to its action upon the muscular tissue. 
The most striking feature of vagus stimulation is a more or less prolonged standstill 
of the heart. There is no reason d priori to assign this standstill to the action of the 
nerve upon the rate of the discharges from the motor ganglia rather than to its action 
upon the muscular tissue of the heart. Either conception is perfectly possible, and its 
truth can be tested directly by experiment. 
* Pflugee’s Arcliiv, Bd. xviii., S. 172. 
f Ibid., Bd. ix., S. 83, 
