174 
DR. A. D. WALLER OR THE ELECTROMOTIVE CHARGES 
is (1) negativity of apex followed by (2) negativity of base. Contrary to the case of 
the Frog, in which the normal variation has its initial phase at the base and its 
terminal phase at the apex of the ventricle, the normal variation of the Mammalian 
ventricle exhibits an initial phase at the apex and a terminal phase at the base. In 
onr previously quoted paper on the excised Mammalian organ. Dr. Deid and I stated 
(p. 230) that “ in the spontaneous beat of the excised organ the contraction of the 
apex generally appears to precede that of the base.” Out of 25 observations,''' in 
17 the mechanical effect of contraction manifested itself at the apex first, in 2 at the 
base first, in 6 there was no appreciable difference. Taken by themselves, these 
observations went to show that the contraction of the Mammalian heart normally 
commences at the apex. But the electrical observations by which we sought to 
confirm this testimony obtained by the mechanical method failed entirely and obliged 
us to state! “that, as regards the electromotive changes with vusible spontaneous 
beats, our results show no uniformity ; we can find in them no evidence either for or 
against the results we obtained by the graphic method.” Observation of the electrical 
variation of the heart beating in situ shows it to be, in the majority o f cases examined 
(11 out of 17), composed of (1) negativity of apex, (2) negativity of base; having 
regard to the fact that the organ is unstable and dying, we may expect to meet with 
exceptions to the rule, which, although by no means invariable, has been frequently 
enough verified to allow us to say of the Mammalian ventricle “ apex first ” with 
])early as much certainty as we say of the Frog’s heart “base first.” As will be 
shown in Part II., the electrical phenomena of the Human heart afford strong con¬ 
firmation of this view. 
I must admit, however, that these observations on the exposed organ in situ have 
been the most troublesome and unsatisfactory in respect of theii' irregidarities ; six 
exceptions as compared with eleven “regular” results is a considerable proportion, 
and I have, therefore, sought by further observations to realise the effect of modifying 
circumstances, and the possible sources of irregularities. I will deal with these points 
seriatim. 
A source of fallacy. —A possible source of an error of observation arises from the 
application of electrode B in close proximity to the auriculo-ventricular groove or in 
actual contact with the auricle. Under these circumstances, the auricular contraction 
may Influence the electrical reading, which must not therefore be attributed to the 
ventricle alone; an electrometer reading in reality due to auricular followed by 
ventricular negativity might be taken to represent basal followed by apical negativity 
of the ventricle alone. If tlie auricles should be beating w'lth a more rapid rhythm 
than the ventricles (as commonly occurs in the moribund Mammalian heart), there will 
obviously be no danger of confusing auricular with basal negativity ; but, if auricles 
and ventricles should be beating in regular sequence, it is necessary to be on guard 
* Log. cit., p. 249, Table H. 
t Loc. cit., p. 234. 
