1913.] 



Electrical Axis of the Human Heart. 



515 



magnitudes of the systolic spikes of the right lateral and left lateral leads 

 respectively. (In the illustration we have taken E = 3 and L = 1.) 



It is scarcely necessary to give the geometrical construction from which 

 the formula is derived. As in the previous case we have tan « = the 

 difference E— L divided by the sum E + L and multiplied by FV/EV, the 

 cotangent of \ the angle EFL. For the superior triangle we took 

 MV/EV = 1, for the inferior angle we take FV/EV = 2. 



The application of our formula may be illustrated by examples. It has 

 been observed, e.g., that E = 3 and L = 1 ; then 



tan 01 — 2 - — - = - = 1, 



4o c 



3 + 1 4 



It has been observed, e.g., that E = 3 and L = — 1 ; then 



3+l 8 , 

 tan a = 2_=- = 4, 



« = 76°. 



We shall now apply our formula to some actual cases : — 



The Case of B. 0. B. 

 (Inspiratory Values.) 



Eight superior 7 "5 



Left superior 17 '5 



(Transverse 16) 



Eight lateral 23 : 5 



Left lateral 15 - 5 



Sup. tan a = L^» 172^? = 12 = 0-40, 

 ^ L + E 17-5 + 7-5 25 ' 



Inf. 



tan a 



R - L = 2 23 - 5 -, 5 - 5 = ^=0-41, ... a = 22= 



E + L 



23-5 + 15-5 39 



