Electrical Axis of the Human Heart. 57 



are thus taken to be represented by a single point F. The right-hand lead 

 RF, being most parallel to the normally oblique current-axis, is the strong 

 lead; the left-hand lead, being least parallel to the current-axis, is the weak 

 lead. 



The general formulae for the inferior leads are : — 



For right-hand values — --7- x cos (F/2 — « 



For left-hand values — --— x cos (F/2 + a), 



cos 1/2 



and for calculation of a from known values of K and L 



tan « = cot — x — — - . 



2 E + L 



In Part I the angle F has been taken as 53°, so that F/2 = 26*5° and 



tan « = 2=^ — — . The values of E and L at different values of « are now — 

 E-f L 



For the right side — ■ — — _ n x cos(26'5° — «), 



cos 26~o 



For the left side — x cos (26 - 5° + «). 



cos 26 - 5° 



The results come out as follows : — 





Right inferior 

 cos (26 -5°-a)/cos 26 -5°. 



Left inferior 

 cos (26 -5° + a)/cos 26 -5 C . 





 



1000 



1000 



10 



1071 



898 



20 



1110 



769 



30 



1115 



617 



40 



1086 



445 



50 



1024 



261 



60 



932 



68 



70 



811 



-126 



80 



665 



-317 



90 



500 



-500 



Similarly, we may work out the values of the leads which have been 

 assumed above as identical, i.e. right lateral and axial, left lateral and 

 equatorial. But it would be tedious and unnecessary to give this in detail, 

 since, as will presently be seen, the results are most easily and quickly 

 obtained by a geometrical model, which gives immediately the results that 

 have been considered up to this point. This model is intended also to 

 render evident the meaning of the apparent discrepancies between vertical 

 and horizontal hearts as regards the effects of respiration, and to give 



