178 
DR. A. D, WALLER ON THE ELECTROMOTIVE CHANGES 
Another instance of the same kind, but in which negativity is twice marked at the 
base, is given in the note to Experiment 5. 
It is possible that in some cases differences of temperature are accountable for 
irregular variations of this character. If, for instance, the base should happen to be 
warmer than the apex, the negativity of the latter wiU outlast that of the former, and, 
if an excitatory process should begin at the apex, it will possibly be twice manifested, 
once before the beginning' and once after the termination of basal negativity. Vice 
versd, if the apex should happen to be the warmer, an excitatory process commencing at 
the base might be twice manifested at each ventricular contraction. Obviously, these 
suppositions require to be submitted to the test of experiment, and I intend to do so 
as soon as time will allow. At present, however, as will be seen, I am led to pursue 
the phenomena in another direction, and I have mentioned the supposition now only 
for the sake of completeness. 
§ 3. Observations on Animals with One or Both leading-oj^ Electrodes applied to the 
Body at a Distance from the Heart. 
The observations to be described in this section lead up to those which will be 
discussed in Part II. They are the steps by which I gradually learned on animals 
what parts of the body are equivalent to leads-off from base and from apex of 
the ventricles. Instead of exposing the heart and leading off from it by both 
electrodes, I led off by only one electrode from the exposed heart and by the other 
from various distant parts of the body; finally, I led off by both electrodes from 
various distant points on the intact animal. 
Experiment 5. — Cat. April 12, 1888. Death by decapitation. Five min. post 
mortem, heart exposed. Electrode A from apex to Hg. Electrode B from stump of 
neck to HoSO.^. 
Spontaneous variations, SN alternating with SNS. Electrode B shifted from neck 
to base of heart. 
Spontaneous variations, SN alternating v/ith SNS. Thus it appears that the lead- 
off from the neck was ecpiivalent to a lead-off from the base of the heart. 
Note. —The alternation, SN and SNS, noticed in this case was observed to coincide 
with a well-marked bigeminal character of the contra'ctioiis of the heart, which was 
beating slowly. The contraction of the base of the heart, upon which electrode B 
was applied, was evidently stronger at each SNS variation than at each SN variation. 
(S indicates base negative, N indicates apex negative.) Thus in this case the 
excitatory process originated at the base, and at every other beat when the base 
contracted more strongly, the negativity was twice manifested at the base. I have 
several times noticed this form of electrical disturbance. 
Experiment 6.— Cat. April 17, 1888. Killed by decapitation ; heart exposed. 
