998 
DR. W. H. GASKELL OK THE RHYTHM OE THE HEART OE 
a series of single induction shocks of sufficient strength, sent through the muscle at'a 
definite and invariable rate, will cause a synchronous series of contractions; and that 
if then the muscle be cooled down, the same series of single stimuli will cause a series 
of contractions synchronous not with every stimulus, but with every second stimulus. 
Again, v. Basch* has shown that a series of single stimuli of the same strength may 
cause a series of contractions synchronous with every second stimulus when each 
stimulus is so weak as to be unable to cause a contraction by itself. 
From these two observations we may draw the conclusion that a definite relation 
between the strength of the stimulus and the excitability of the ventricular muscle is 
necessary, in order that the muscle should contract synchronously with the series of 
artificial stimuli; and also that the muscle may be made to respond synchronously to 
every second stimulus, instead of to every stimulus, either by lowering the excitability 
of the muscle, the strength of the stimulus remaining unaltered, or by lessening the 
stimulus, while the excitability remains the same. 
In his latest paper,! v. Basch suggests as an explanation of this half-rhythm that 
a stimulus which is insufficient to cause a contraction increases the excitability of the 
muscle, so that a subsequent stimulus of the same strength is thereby enabled to 
produce a contraction. 
These observations of Kroneck^r and v. Basch may be taken as evidence that the 
ventricular muscle is able to sum up the effects of two or even more artificial stimuli; 
but so far we have no proof that it is able to act in the same way towards the normal 
impulses coming from the motor ganglia. 
This evidence I have been able to supply by my method of experimentation, and 
have come to the conclusion that a definite relation between the strength of the 
impulses from the motor ganglia, and the excitability of the ventricular muscle, is 
requisite to ensure the occurrence of a series of ventricular beats synchronous with the 
impulses coming from the motor ganglia. Here, too, j ust as in the case of the artificial 
stimuli, a certain number of the impulses prove inefficient to cause a contraction when 
the excitability of the muscle is lowered sufficiently; here, too, a diminution in the 
strength of the impulses below a certain limit causes the ventricle to beat synchronously 
with every two, three, or more impulses, instead of with every impulse, although the 
excitability of the muscle remains the same. 
In this case, then, as well as in the case of artificial stimulation, the probable 
explanation of the half-rhythm observed is to be found in the following extension of 
the suggestion made by v. Basch, viz. : when the relation between the strength of the 
impulses coming from the motor ganglia and the excitability of the ventricular muscle 
is such that each separate impulse is not able to cause a beat of the ventricle , then the 
ventricle does not necessarily remain quiescent, but beats synchronously with every second 
* Sitzber. d. k. Akad. d. Wiss. (Wien.) Bd. Ixxix., III. Abth. 
f Arch. f. Anat. u. Physiol. (Physiol. Abth.). 1880, S. 283. 
