524 Dr. A. D. Waller. Various Inclinations of the [Mar. 6, 



find that the first lead is stronger than the second. Taking leads from the 

 back of the chest, and first the right then the left hand, we find that the 



Back 



Mourh 



Posh 



Lefr 



Fronh 



first lead is positive, the second small. 



Taking, e.g. 



Fool" 



the values observed 



for these four leads in the case of B. 0. B. the angles come out as follows :- 



tan x = 1^ — -— = 0-36, 



tan 



16 + 7-5 

 7-5 + 5 



at = 20 c 



« = 79°. 



7-5-5 



The angle formed above the heart by the current-axis with the vertical in 

 this plane can be estimated from the relative values of the spike in the 

 two leads mouth-precordium and mouth-back. Thus, e.g. in the subject 

 B. 0. B., the values of the spike in these leads are : anterior = 25, 

 posterior = 10, from which our formula for the superior triangle gives 

 tan a = (25 — 10)/(25 + 10) = 15/35 = 0-43, so that the required angle 

 « = 23°. The angle below the heart can be obtained by calculation from the 

 values observed in the two leads precordium-foot and back-foot. In the 

 •case of B. O. B. these values are : anterior = —10, posterior = 10 ; 



,10 + 10 



tan a 



10-10 



at = 90°. 



This result may be taken as indicating that for the superior part of the 

 heart and body the algebraic sum of current is to be pictured as an arrow 

 directed forwards and downwards at an angle of 23° with the vertical ; 

 while for the inferior part of the heart and body the current-axis is repre- 

 sented by an arrow directed horizontally forwards at an angle of 90° with the 

 vertical. 



I have tabulated, from my laboratory notes and records of " normal " 

 subjects, the values of right and left hand records, and of the angle a 

 ■calculated from them. 



