56 Dr. A. D. Waller. Various Inclinations of the 





Left superior 

 cos 45° x cos (45° — a). 



Eight superior 

 cos 45° x cos (45° + a). 



■ 







5000 



5000 



10 



5793 



4056 



20 



6409 



2988 



30 



6829 



1830 



40 



7014 



0616 



45 



7071 



0000 



50 



7014 



-0616 



60 



6829 



-1830 



70 



6409 



-2988 



80 



5793 



-4056 



90 



5000 



-5000 



It will be noticed that the right-hand values steadily diminish as the axial 

 angle increases from 0° to 90° from their maximum of 50 to their minimum 

 of —50, passing through the value when « = 45 ; that the left-hand 

 values between « = 0° and a = 90° increase from 50 to a maximum of 

 71 (7071) at 45° and then decrease again to 50. The right-hand lead is 

 " weak," the left-hand lead is " strong." In the strong lead the first 

 ventricular wave Vi is positive in both types of heart — vertical and 

 horizontal. It is increased by inspiration in the horizontal heart, decreased 

 by inspiration in the vertical heart. 



In the formulae given above, for the calculation of the numerical values of 

 right and left superior leads, we have taken the vertical angle at M = 90°, 

 so that the semi-vertical angle M/2 = 45° [and that the formula for 

 calculating « from known values of R and L is : tan a = (L— R)/(L + R)]. 

 Generalising for any value of M the formulae for the superior leads 

 become : — 



M /M \ 

 2 



For left-hand values- 



( «,s — > cos ( — a J . 



\2 



For right-hand values — 



M /M , 



COS — X COS f — + a 



and for calculation of « from known values of R and L, 



,M L-R 

 tan « = cot — . = — = . 



2 L + R 



The right and left inferior leads (right hand and either foot, left hand 

 and either foot) are at first sight somewhat less simple, but they are 

 readily simplified. As was shown in my first observations of 1889, the 

 two feet are practically isoelectric, and we may therefore regard as being 

 electrically identical the two right inferior leads (axial and right lateral) 

 and the two left inferior leads (equatorial and left lateral). The two feet 



