49 



The Various Inclinations of the Electrical Axis of the Human 

 Heart. Part Ia. — The Normal Heart : Effects of Respiration* 

 By Augustus D. Waller, M.D., F.E.S. 

 (Received March 30 —Read May 14, 19i4.) 

 (Plates 3-6.) 



In my first account of the electrical action of the human heart,f I made no 

 allusion to the influence upon the electrical pulse of the movements of 

 respiration. I noticed that influence indeed which is especially well marked 

 in my own case (where the heart happens to be of the complete horizontal 

 type) but only as disturbing the demonstration, and in some cases 

 rendering the direction of the pulse uncertain. I noticed in particular that 

 when demonstrating the transverse effect from the two hands, best effects 

 were shown by holding my breath in expiration, and that these effects were 

 markedly diminished during deep inspiration. I imagined at that time that 

 the effect was due to a disfavouring of current spread from the heart by 

 reason of the distended lung, but was puzzled by the fact that with the axial 

 lead (right hand and left foot) the electrical pulse was augmented during 

 inspiration instead of diminished as was the case with the transverse lead. I 

 did not, however, follow up the clue afforded by this discrepancy, and it was 

 only much later, i.e. after the introduction by Einthoven of the string- 

 galvanometer and the observations of Einthoven, Kraus and Mcolai, Samojloff 

 and others, that the meaning of the discrepancy and with it the whole 

 mechanism of the respiratory effects became clear. The variations of ampli- 

 tude are, if not entirely, almost entirely due to the rise and fall of the 

 diaphragm, raising and lowering the heart as a lever hinged at the aortic end 

 and thus widening and narrowing the "axial angle." . (By axial angle I mean 

 the angle formed with the vertical by the current axis of the heart or line of 

 greatest potential difference at right angles to the equator 00.) 



In 1889 I represented this angle as being 45° to the left (and 45° to the 

 right in cases of situs viscencm inversus), and drew two series of curved 



* The method followed was the same as that followed for the observations of Part I. 

 A Bock-Thoma galvanometer was used for these observations, the deflections being 

 standardised whenever necessary by a millivolt switched into the circuit. For the 

 careful comparison of values in different leads or between the values obtained at different 

 times, a standard millivolt deflection was of course taken, and the proportional correction 

 applied, if necessary. But in comparisons taken between the two sides of the body the 

 standard deflection was found to be so invariable that it was often omitted. 



t " On the Electromotive Changes connected with the Beat of the Mammalian Heart, 

 and of the Human Heart in particular," 1 Phil. Trans.,' B, vol. 80, p. 169 (1889). 



VOL. LXXXVIII. — B. E 



