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THE APEX-BEAT. THE CARDIOGRAM. 



The cause of the ventricular impulse resides in the following factors : 



1. The base of the heart (the junction of auricles and ventricles), 

 which in diastole presents the form of a transverse ellipse (Fig. 29, I, F 

 G), is contracted to a rather circular figure (a b). In this way, the large 

 diameter of the ellipse (F G) is naturally diminished and the small 

 diameter (d c) is increased, and in consequence the base is brought nearer 

 to the chest-wall (e). This alone, however, does not produce the apex- 

 beat, but the base of the heart, thus brought somewhat nearer the chest- 

 wall, and hardened during systole, affords the apex the possibility of 

 making the movement that constitutes the apex-beat. 



2. The ventricles, which during the period of relaxation have their 

 apex (Fig. 29, II, i) directed obliquely downward in the line of their long 



FIG. 29. I. Horizontal Section through the Heart and the Lungs, Together with the Chest-walls, for the Demon- 

 stration of the Change in the Shape of the Base of the Heart during the Contraction of the Ventricles: F G, 

 transverse diameter of the ventricles during diastole; c, position of the anterior ventricular wall; a b, transverse 

 diameter of the ventricles during systole with e, the position of the anterior ventricular wall during systole. 

 II. Lateral View of the Position of the Heart: i, the apex-beat during diastole; p, during systole (in part 

 after C. Ludwig and Henke). 



diameter, so that the angles (b c i and a c i) formed by the junction 

 of the ventricular axis with the diameter of the base are unequal, 

 represent a symmetrical cone, with its axis perpendicular to its base. 

 Accordingly, the apex (7) must be elevated from below and behind for- 

 ward and upward (p) (W. Harvey: "Cor sese erigere"), and it thus 

 thrusts itself, hardened during systole, into the intercostal space 

 (Fig. 29, II). 



3 . During the systolic contraction the ventricles of the heart undergo 

 a slight spiral rotation about their long axes ("lateraleminclinationem," 

 W. Harvey), so that the apex is carried from behind slightly forward, 



