234 
DR. A. D. WALLER AND MR. E. W. REID ON THE 
excitation becomes negative to the proximal electrode. This result is exceptional, 
and, although at first sight anomalous, can, we think, be reasonably explained. We 
think it is due to unequally excitable tissue at the two led-off points, and that the 
inequality consists in diminished excitability near the first lead-off in comparison 
with greater excitability near the second lead-off. Our notes contain several experi¬ 
ments, the analysis of which justifies this conclusion, and we may refer to Experi¬ 
ment No. 31 (Remarks on Galvanometer Experiments) as an instance in point. 
We have never seen a diphasic variation such as to indicate negativity starting 
from the distal electrode. These results are in agreement with those previously 
described under § V. (a). We have usually applied our electrodes near the base and 
near the apex of the ventricle, both right and left; we have also applied them 
laterally to the right and left border of each ventricle. We have also examined the 
variations with an electrode on each ventricle, and with one electrode upon the 
auricle, the other on the ventricle. As regards all positions of the electrodes on the 
two ventricles, we have observed that the diphasic variation is the rule by excitation 
near either electrode. Our observations go to show that the ventricular portion of 
the excised Mammalian heart is an indifferent physiological conductor of the excited 
impulses in all directions. There are in the ventricular mass no indications of 
directions of greater or less resistance to the passage of the excitatory state. As 
regards the junction between auricle and ventricle, we have never seen any 
evidence of the passage of negativity in either direction. When an electrode is 
placed on either auricle and ventricle respectively of the same side, and excitation is 
applied to either cavity, the result has always been a single variation indicative of 
negativity of the electrode applied to it. We have never obtained a diphasic 
variation, nor have we ever observed a diphasic variation with electrodes on each 
auricle. These statements are based on experiments made after spontaneous contrac¬ 
tions had ceased, viz., half to two hours after excision of the heart. 
(b.) Spontaneous contractions .—As regards the electromotive changes with visible 
spontaneous beats, our results show no uniformity ; we can find in them no evidence 
either for or against the results which we obtained by the graphic method. The 
direction of the deflection when the heart was connected with the galvanometer by 
base and apex was very variable, and indicated no regular origin or mode of progres¬ 
sion of the excitatory process. We can say no more on this point than that out of 
62 experiments we observed N in 17 cases, S in 17, NS in 16, and SN in 12. 
Under these circumstances, and in the anticipation that this difficult question may be 
further pursued, and the conditions of variety in results determined either by ourselves 
or by others, we think it best to place on record a tabular summary of our results 
(Table I.), in the hope that the data therein consigned may prove to be of further use. 
We intend to pursue this question in a future investigation. 
