THE APEX-BEAT. THE CARDIOGRAM. 103 



while at the same time a considerable area of the left ventricle is turned 

 forward. This rotation is due to the fact that many of the fibers of 

 the ventricular muscles that arise from the portion of the fibrous ring 

 that is turned toward the chest-wall at the junction of the right auricle 

 and ventricle pass obliquely from above and to the right downward and 

 to the left, in part to the posterior aspect of the left ventricle. Thus, 

 they draw the apex of the heart upward in the direction of their course, 

 and its posterior aspect slightly toward the anterior wall of the thorax. 

 This rotatory movement is favored by the circumstance that the aorta 

 and the pulmonary artery, which are applied to each other in a slightly 

 spiral manner, effect a rotation of the heart in the same direction at the 

 time of systolic tension. 



According to an earlier opinion the cardiac impulse was held to be produced 

 or at least increased by : 



4. The recoil that the ventricles are supposed to experience (like a dis- 

 charged firearm) at the instant when the column of blood empties itself into the 

 aorta and the pulmonary artery. The apex would, of course, be driven in the 

 opposite direction by this recoil, that is, downward and a little outward. Landois, 

 however, has pointed out that the blood-column is discharged into the vessels 

 0.08 second after the beginning of the ventricular contraction, while, on the other 

 hand, the apex-beat begins simultaneously with the first sound. 



As, however, the apex-beat is observed in bloodless hearts taken 

 from animals after death, and as the apex of the heart is not, as it 

 would be on the theory of the recoil, displaced downward and to the 

 left during systole, but upward and to the right (as has been confirmed 

 by v. Ziemssen in a woman whose heart was exposed), the recoil cannot 

 be regarded as a factor in the problem. 



After the ventricles by their systolic movement have traced the 

 greatest part of the apex-beat curve, as far as its apex (c), the curve 

 rapidly descends and the ventricles pass from a state of extreme con- 

 traction to one of relaxation. Soon, however, two small elevations 

 appear in the descending limb of the curve at d and e. These are due 

 to the abrupt closure of the semilunar valves, which, being effected with 

 a certain degree of force, is transmitted along the axis of the ventricles 

 as far as the apex, and through the latter even causes concussion of the 

 intercostal space; d corresponds to the closure of the aortic valves, e to 

 that of the pulmonary valves. The valves, therefore, do not close at 

 the same time, there being an interval of about from 0.05 to 0.09 second 

 on the average. Owing to the greater pressure of the blood in the 

 aorta the aortic valves close earlier than those of the pulmonary artery. 



While investigators are agreed that the first sound of the heart begins at 

 the point b of the cardiogram, various statements have been made with regard 

 to the point at which the registration of the second sound of the heart takes place. 

 Martius designates the depression between c and d (Fig. 28, E) as the point that 

 corresponds to the second heart-sound; Landois the apices d and e, when the 

 tension of the semilunar valves is increased; Hiirthle, Einthoven and Geluk 0.02 

 second after e; Marey and Fredericq about midway between e and f ; and, finally, 

 Edgren at a point immediately in front of f . 



Method. In order to determine the time when the heart-sounds are heard, 

 their vibrations are transmitted to a microphone attached to the thorax. The 

 instrument, which is thrown into vibration by each sound of the heart, opens 

 and closes an electric circuit with each vibration and thus attracts an electromagnet, 

 or sets a capillary electrometer (Fig. 229) in motion. If by means of another 

 contrivance the cardiogram is made to register at the same time, the points on 

 the latter at which the heart-sounds are heard can be seen. 



From the point e to the foot of the curve (at f) comprises the time 

 during which complete diastolic relaxation of the ventricles takes place. 



