Electrical Axis of the Human Heart. 



51 



normal type. The consideration of the effects of respiration appeared to me 

 at that time as a side-issue to be cleared up by a few carefully planned 

 observations, whereas it now presents itself as an extremely simple exercise 

 in elementary trigonometry on the main line of the principal argument. 



The essential distinction between favourable or strong leads (left superior 

 and right inferior) and unfavourable or " weak" leads (right superior and left 

 inferior) which was the principal result of my first investigation of the subject, 

 afford, when their data are converted into simple ratios, sinusoidal curves 

 which plotted upon millimetre paper exhibit directly the quantitative relations 

 between the electrical effects of the heart, whether horizontal or vertical (as 

 described in Part I) or at various inclinations in accordance with respiratory 

 alterations of the cardiac axis. 



The facts will be best presented by a detailed account of two typical cases. 



The Case of B. 0. B. — An Ollique Heart. 



Fig. 2 (Plate 3) gives the transverse, right inferior and left inferior records 

 taken simultaneously with the record of respiration slow and deep so as to 

 emphasise the effects upon the heart, which in this subject had been 

 determined as having an electrical axis forming an angle not exceeding 30° 

 with the vertical during quiet breathing. 



The amplitude of the spike in the transverse record varies between a 

 maximum of 20 mm. in expiration and a minimum of 15 mm. in inspiration. 

 The waxing and waning is very regular and at once suggests a sinusoidal curve. 



In the right inferior record the respiratory variation of amplitude is much 

 less pronounced and regular within a range that may be taken as 27'5 mm. 

 in expiration and 24 mm. in inspiration. 



In the left inferior record the variation is regular and large and suggestive 

 of a sinusoidal curve. The range is measured as between the values = 6 mm. 

 immediately after the culmination of expiration, and = 14 mm. during 

 inspiration. (In these three records the deflection by 1/1000 volt through 

 body and galvanometer was 18 mm.) 



Prom these values right and left below the heart we calculate that : — 



1-28, .-. a = 52°. 



0-53, .-. a = 28°. 

 Diff. = 24°. 



In the right superior record the respiratory variation is small and fairly 

 regular between values that may on the average be taken as = 5 mm. in 

 expiration and = 7'5 mm. in inspiration. 



E 2 



2^.Fj Q 



The expiratory tan <x = 2 — — 



- J 27-5 + 6 



The inspiratory tan a = 2 ^4— 14 

 F J 24 + 14 



