1913.] 



Electrical Axis of the Human Heart. 



509 



The facts have been confirmed by all subsequent observers, more or less 

 completely according as they have reviewed more or fewer of the 10 leads, 

 but with one notable exception, viz., the left lateral, as to which I am stated 

 to have been mistaken. Prof. Einthoven in particular has attributed my 

 having classified it as an " unfavourable " or " weak " lead to the comparative 

 slowness of the capillary electrometer ;* as a matter of fact I did not make 

 the mistake attributed to me, and I expressly adhere now to my original 

 classification of the left-hand lead with either foot as a " weak " lead. The 

 classification of leads as " strong " and " weak " forms indeed the basis of this 

 paper, in the course of which it will be made apparent that the relatively 

 weak left-hand effect below the heart is an index of the degree of obliquity 

 of the cardiac current-axis. 



f R. hand. 



1. Transverse... -I 4. L. lateral 



LL. hand. 



2. Axial 



3. R. lateral 



7. L. superior .. 



R. hand. 

 L. foot. 

 R. hand. 

 R. foot. 



(" Mouth. 



5. Equatorial 



6. Inferior , 



a: 



L. hand. 



foot. 

 L. hand, 

 foot. 



10. R. superior .. -| 



[L. hand. 



r Mouth. 



8. L. inferior ... < 

 I L. foot. 



f Mouth. 



9. R. inferior... <! 



L R. foot. 



C C denotes the current-axis, O denotes the equator. 



R. foot. 

 L. foot. 



f Mouth. 

 R. hand. 



When the survey of these ten leads has been completed, we may reduce 

 them in number for further systematic investigation. The two feet are 

 practically iso-electric : this pair may therefore be neglected. And if we 

 regard the two feet as electrically indifferent, the axial and right lateral 

 leads are equivalent, and one of them may be left out ; also, on this assump- 

 tion, the left lateral and the equatorial are equivalent, and we may drop one 

 out. Then as to the mouth ; it is not necessary in a cursory survey to take 



* Einthoven (' Pfluger's Archiv,' 1908, pp. 551-2). In my first three cases of 1887 the 

 angles (measured in 1913) are 45°, 51°, and 86°. In Einthoven's two cases of 1908 

 (measured from the published records on pp. 554-5) the angles are — Ei. = 22° and 

 Fl. = 7°. 



2 P 2 



