996 
DR. W. H. GASKELL OR THE RHYTHM OF THE HEART OF 
clamp without touching the ventricle; so that it is possible to increase or diminish the 
excitability of the ventricular muscle without affecting the discharges from the motor 
ganglia, or to act upon the motor ganglia without altering the excitability of the 
ventricle. Of the various means, for effecting this object, it will be sufficient to give 
examples of the action of heat, atropin and muscarin. 
When the whole heart is heated the rate of rhythm is always greatly increased, 
and the same, as is well known, is true in the case of either the ventricle or apex when 
isolated and beating spontaneously. In this latter case the greater rapidity of rhythm 
is partly, at all events, to be ascribed to the increase of excitability in the muscle due 
to the heating. 
Suppose, now, in the heart suspended as described above the ventricle alone be heated, 
then its excitability will be increased - * while that of the auricles will remain the same 
as before, and therefore if the rhythm be dependent upon the muscular tissue, as in the 
case of the isolated apex, the ventricle ought to beat at a quicker rate than the 
auricles whose excitability has not been altered. On the other hand, if the rhythm is 
due to discrete impulses passing from the motor ganglia to the ventricle, then no 
increase in the excitability of the latter ought to make the smallest alteration in the 
rate of the beats, because upon that view the ventricle does not contract except when 
an impulse reaches it, and the motor ganglia remaining outside the range of the heating 
the rate at which their discharges take place remains unaltered and is unaffected by 
any alteration in the excitability of the ventricular muscle. Of these two views 
experiment proves that the latter is the true one. 
If the clamp be placed in the auriculo-ventricular groove and be tightened so as 
just to hold the tissue firmly, then both auricles and ventricle continue to beat with 
perfect regularity for hours, each ventricular beat following in orderly sequence upon 
each auricular. In order to heat the parts of the heart on one side of the clamp 
without heating those on the other side I have used a spiral of thin platinum or 
copper wire which is placed round either the ventricle or the auricles and sinus and 
is in connexion by means of a key with a battery of two or three Grove cells. When 
the ventricle alone is to be heated it is placed in connexion with the upper lever and 
the auricles with the lower; if the heating is intended to affect only the sinus and 
auricles then the arrangement is reversed. That this method works well is shown by 
the fact that whereas a thermometer suspended within the spiral may show a rise up to 
50° or 60° C. under the heating influence of three Grove cells, yet a thermometer 
placed against the tissue just below the clamp does not show 7 any rise at all, when the 
spiral is in position round that part of the heart which is situated above the clamp. 
Heating the sinus and auricles alone in this way causes a most marked increase in 
the rate of. rhythm both of the auricles and ventricle, with other phenomena which 
will be mentioned presently (Plate 67, fig. 1), showing that the method of heating is 
effective. On the other band, when the ventricle alone is heated no alteration in the 
* Kroneckeb, “ Das charact. Merkmal der Herzmuskel-Beweg.” Ludwig’s Festgabe, 1874. 
