ACTION OF THE EXCISED MAMMALIAN HEART. 
233 
Kolliker and Muller,* that the spontaneous systole of the Mammalian heart is 
accompanied (or rather preceded) by an electromotive change ; to this we have to add 
that the electromotive change is frequently diphasic, and entirely similar to the 
diphasic variation of the spontaneously beating Frog’s heart. The second chief fact 
relating to spontaneous action is that electromotive changes, such as ordinarily belong 
to visible contraction, frequently persist in the absence of such visible contractions, 
and continue long after these have entirely ceased, i.e., invisible molecular changes 
outlast visible changes of form. 
(a.) Excited contractions .—As regards excited beats, one fundamental result is that 
excitation applied near to one of two points, by which any two parts of the excised, 
but otherwise uninjured and quiescent, heart are led off to the galvanometer, gives 
rise to a diphasic variation the direction of which is such as to indicate (1) negativity 
of the proximal electrode; (2) negativity of the distal electrode. These are the most 
important points which we have been able to satisfactorily establish. To these may 
be added a fourth statement, viz., the effect of local injury long after the heart has 
become quiescent, i.e., inexcitable, and is apparently dead, is to develop a local 
alteration of potential, the injured part becoming negative to all other parts. 
The details of our experiments show many irregularities, some of which we can only 
partially understand, but which are doubtless attributable to irregularities and 
inequalities in the dying organ; these may have been due to differences of tempera¬ 
ture or accidental injuries, or other spontaneously occurring inequalities of excitability 
at different points. It might be expected that an explanation of these should be 
found by the experimental establishment of such irregularities : we have sought for 
such an explanation and failed to find it; and we attribute this failure to the great 
susceptibility of the excised Mammalian heart to experimental interference. Our 
laboratory notes contain abundant examples of this extreme susceptibility to 
apparently trivial causes. To mention an example, we have frequently noticed that a 
slight touch with a blunt pointed instrument near one of our two electrodes was 
sufficient to develop 'permanent negativity at the part, indicative of a slight degree of 
injury. It consequently happened, as the most frequent exception to the classical 
effect, that instead of the diphasic variation, indicative of negativity at the first and 
second contacts respectively, we obtained only a simple variation. We think that 
the apparent local negativity developed under these conditions was in different cases 
attributable to either of two causes: (1) injury; (2) the excitatory state. The first 
cause is indicated by a single permanent deflection, the second by a single swing ; and 
that this is an excitatory effect is indicated by the fact that the first variation 
consequent on excitation is often followed by a second or a third'such variation, and 
that the series of single variations thus initiated may terminate with a typical 
diphasic variation. We have exceptionally noticed that local excitation might give 
rise to a single variation, indicating that the electrode furthest from the point of 
* ‘ Wurzburg, Phys. Med. Gesell. Verhandl.,’ vol. 6, 1856, p. 529. 
MDCCCLXXXVII.—B. 2 H 
