184 
DR, A, D, WALLER OR THE ELECTROMOTIVE CHARGES 
applied to the apex of the ventricle, shows the comparative effects of auricular and 
ventricular events ; it will not be surprising that, if both electrodes be applied to the 
periphery, only the latter event should be manifested. 
With respect to the distribution of cardiac electrical potentials ascertained by the 
determination of “ favourable” and of “unfavourable” leading-off points of the body, 
this, although it properly belongs to Part I., will be more conveniently considered in 
conjunction with the study of cardiac potentials on Man. 
Part II. 
Electrical Variations of the Heart on Man. 
I now pass to the more important series of observations, to which those described 
in Part I. were the experimental preface. 
It should first be recalled that, of the various points established in this preface, 
four in particular have a special bearing upon the due interpretation of the observa¬ 
tions about to be described. 
1 . The normal variation of the Mammalian ventricles is diphasic. 
2 . The variation can he observed on the intact animal by leading of'from p>oints 
of the body remote from the heart. 
3 . Under these circumstances the auricular contraction gives no electrical 
indication. 
4 . A lead-off from the mouth is equivalent to a lead-off from the base of the 
ventricles; a lead-off from the rectum or from a posterior extremity is 
equivalent to a lead-off from the apex. 
An investigation made last year upon my own person gave the following results^":— 
Leading off from the surface of the body by the several limbs and from the mouth, 
I found that some combinations were favourable, while others were unfavourable,t to 
the demonstration of the cardiac variation. The favourable combinations were the 
following :— 
Front of chest and back of chest. 
Left hand and right hand. 
Right hand and right foot. 
Right hand and left foot. 
Mouth and left hand. 
Mouth and right foot. 
Mouth and left foot. 
* ‘ Journal of Physiology,’ vol. 8, p. 229. 
t I iise the terms “favourable” and “ unfavoui’able ” for the following reason:—With a modeiutely 
sensitive electrometer no variation is seen with an unfavourable combination, and a small variation is 
seen with a favourable combination; with a very sensitive electrometer a small variation is seen with an 
unfavoimable, and a comparatively large variation with a favourable, combination 
