518 Dr. A. D. Waller. Various Inclinations of the [Mar. 6, 



There is no more than a general correspondence of inclination between the 

 line drawn through the heart to represent its anatomical axis and the line or 

 lines representing its electrical axis. This is hardly surprising when we 

 realise how indefinite is the anatomical axis and upon what data and assump- 

 tions the determination of the electrical axis depends. I regard the latter as 

 the more definite of the two lines; it gives expression to the functional 

 resultant at the outset of contraction of the living organ, and indicates by 

 considerable and definite variations changes of axis that are difficult to settle 

 either post mortem or by skiagram during life. 



6. Tone of the Heart Muscle. 



I attribute considerable importance to the tone of the heart muscle as 

 regards position of the heart and of its electrical axis. With soft muscle the 

 heart is sessile on the diaphragm, and the axis, as calculated from right and 

 left lateral spikes, is approximately horizontal. (See fig. on p. 520, the case of 

 Dr. E.) With hard muscle the heart is more nearly erect on the diaphragm, 

 and the axis, calculated as before, is more nearly vertical. (See fig. on 

 p. 521, the case of Dr. D.) 



Influence of Respiration. — I paid no attention in my first observations to 

 the effect of respiration upon the electrocardiogram. This effect has since 

 been' carefully studied by Einthoven, who has shown that with forced 

 inspiration the amplitude of the record of Lead III (left lateral) is increased, 

 while that of Lead I (transverse) is diminished ; the changes in Lead II 

 (axial) he describes as very slight. My observations are on the whole in 

 harmony with those of Einthoven, but their full discussion must be post- 

 poned. For the purpose of the present communication it will be sufficient 

 to state that I have found it necessary for any exact estimation of the angle 

 to take into account the phases of ordinary respiration, which briefly are of 

 the following character : — 



With inspiration the left superior and the right lateral records are dimin- 

 ished, the right superior and the left lateral records are increased. In taking 

 out values of E and L for a careful determination of « by the appropriate 

 formulas it is therefore necessary to take for its inspiratory value the smallest 

 values recorded of the left superior and right lateral leads and the largest 

 values recorded of the corresponding right superior and left lateral leads 

 For the expiratory value we must take out the largest values of the left 

 superior and right lateral and the smallest values of the right superior and 

 left lateral. But this troublesome correction is in most cases superfluous. 

 It can, however, occur that normal respiration brings out differences of 

 amplitude that lead to differences of angle of 10°, e.g. the case of J. B. F., 



