1000 
DR. W. H. GASKELL OH THE RHYTHM OE THE HEART OF 
through such intermediate stages as 1 ventricular to 5 auricular, 1 to 4, 1 to 3, it 
settles down to the rhythm 1 to 2, at which it remains permanently, or ultimately 
returns to a rate synchronous with the auricular (Plate 67, fig. 3). 
In some cases the rhythm of the ventricular beats has remained for a long time 
synchronous with every third beat of the auricles, instead of every second, as in 
Plate 68, fig. 14, and in other cases, for a shorter time, with every fourth beat. This 
latter rate of rhythm occurs frequently in the apex of the heart when the clamp is 
placed across the middle of the ventricle and the beats of the apex and base of the 
ventricle are compared (see Plate 69, fig. 16); here, too, however, the more permanent 
rate caused by the compression of the clamp is that in which the apex beats synchro¬ 
nously with every second beat of the base. 
These facts show that direct compression of the tissue between the motor ganglia 
and the ventricle causes a certain number of the impulses to be ineffective as far as the 
causation of a ventricular beat is concerned, although, as shown by the auricular beats, 
that compression has not interfered with the rate of discharge from the ganglia. 
Either, then, the compression of the clamp in the auriculo-ventricular groove has 
caused a diminution in the excitability of the ventricular muscle without altering the 
strength of the impulses coming to it, or it has diminished the strength of the impulses 
to the muscle and so caused it to respond to every second instead of to every impulse. 
Which of these two solutions is the most probable will be better discussed after the 
consideration of the effects upon the ventricular rhythm of heating the auricles and 
sinus only, and of the application of poisons to the ventricle alone. 
When by the method described above the auricles and sinus alone are heated, any 
variations which are noticed in the rhythm of the ventricle must be due to the action 
of the heat upon the motor impulses before they have reached the ventricular muscle 
and not to any alteration in the excitability of the muscle itself, for the latter is out of 
the. range of the heating. 
In many respects there is a decided resemblance between the action of the clamp and 
the effect of heating the auricles and sinus upon the rhythm of the ventricle. Thus, if 
the heating has been sufficient only slightly to accelerate and diminish the auricular 
contractions, then it is found that the ventricle is able to beat synchronously with the 
accelerated auricular beats, just as a slight compression of the clamp does not interfere 
with the regular sequence of ventricular upon auricular beats. If the heating continues 
the auricular beats become weaker and more rapid, and the curves then show that 
the ventricle is unable to respond with the same rapidity, and ceasing suddenly to 
beat synchronously with the auricles, it answers with a single contraction to every 
two contractions of the auricles. When the heating is removed and the auricles 
begin to beat less frequently/the ventricle again alters its rate so as to beat synchron- 
ouslv with the auricles with the same suddenness as in its original alteration of 
rhythm. So, too, an increase in the tightness of the clamp makes the ventricle beat 
