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XXIII. The Croonian Lecture. — On the Rhythm of the Heart of the Frog, and 
on the Nature of the Action of the Vagus Nerve. 
By W. H. Gaskell, M.D., Cant. 
Communicated by Dr. Michael Foster, Sec. R.S.,from the Physiological Laboratory, 
Cambridge. 
Received December 8,—Read December 22, 1881. 
[Plates 66-70.] 
In all investigations upon the causation of the beat of the heart, one question stands 
forward prominently before all others, viz. : What is the relative share taken by the 
ganglion cells and the muscular tissue respectively in the production of its spontaneous 
rhythmical beats ? And in any discussion upon the action of the cardiac nerves, the most 
important question always is, How far do they act on the ganglion cells, how far on 
the muscular tissue directly? 
In recent times a variety of investigations have pointed unmistakably to the con¬ 
clusion that rhythmical action can occur in muscular tissue under the influence of a 
constant stimulus without the intervention of ganglion cells, or at all events of any 
well-defined recognisable nerve-cells; in other words, certain kinds of muscular tissue 
possess the faculty of transforming the effects of a continuous stimulus into a dis¬ 
continuous result. 
Again, there can be no doubt whatever that in the heart of the Frog the rhythmical 
beat is markedly associated with the presence of certain ganglion celis, especially the 
cells of Remak’s ganglia, so that the first question which it is absolutely necessary to 
answer is, Does the normal rhythm of the heart as a whole depend upon separate 
rhythmical impulses passing from certain motor ganglia to the muscular tissue, each of 
which impulses causes a contraction, so that the rhythm is due to the nerve cells, and 
the muscle simply gives expression to it, or do the motor cells send to the muscles a 
continuous series of subminimal impulses, the effects of which the muscle sums up, so 
as to produce from time to time a single beat; in other words, Is the rhythm due to 
the muscle, while the nerve cells supply the constant stimulus ? 
Further, before it is possible to consider the action of the cardiac nerves, it is neces¬ 
sary to come to some conclusion respecting the different attributes of the cardiac 
muscle apart from the question of rhythm, and it seems to me that the three which 
especially demand attention are the following :—- 
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