TIME-RELATIONS OF THE MOVEMENTS OF THE HEART. 105 



does not coincide with b, as from 0.085 to -73 to 0.06 second elapses between the 

 beginning of the ventricular contraction and the opening of the semilunar valves 

 of the aorta. According to this calculation the entrance of the blood into the 

 aorta (aortic inflow) would occupy from 0.08 to 0.09 second. Landois arrived at 

 this result by the following calculation: The interval between the first sound of 

 the heart and the pulse at the axillary artery is 0.137 second. The propagation 

 of the pulse-wave along the distance from the root of the aorta to the axillary 

 artery, which is equivalent to 30 centimeters, cannot occupy more than 0.052 

 second of this time (corresponding to the analogous velocity in the distance -50 

 cm. from the axillary to the radial artery = 0.087). Hence, the pulse-wave in 

 the aorta cannot take place earlier than 0.137 minus 0-052 =0.085 second after 

 the beginning of the first sound of the heart. Landois found in agreement with 

 Hurthle that in some cardiograms the point that marks the beginning of the flow 

 of blood into the arteries, or, what is the same thing, the time of the opening of 

 the semilunar valves, is indicated in the ascending limb by a small interval between 

 b and c. The current in the pulmonary artery is not interrupted until the point 

 e is reached. 



3. Finally, the time occupied by the muscular contraction of the ventricle 

 may be considered. The contraction begins at b, reaches its greatest degree at c, 

 and is not followed by complete relaxation until f is reached. The apex of the 

 curve c may, however, be higher or lower, according as the intercostal space 

 yields more or less; the position of c is, therefore, variable. 



The time that elapses between d and e, that is, between complete 

 closure of the semilunar valves and of the pulmonary artery, is greater 

 in proportion as the pressure within the aorta exceeds that within the 



FIG. 30. Contraction-curves from the Ventricle of a Rabbit Registered on a Plate Attached to a Vibrating Tuning- 

 fork (one vibration m 0.01613 second): A, soon after death; B, taken while the ventricle was in process of 

 dying. 



pulmonary artery, as the closure of the valves is effected by the pres- 

 sure from above. This interval may vary from 0.05 second to more 

 than twice that length of time; in the latter event the second sound of 

 the heart is also duplicated. If, however, the tension in the aortic 

 system diminishes and the pressure in the pulmonary artery rises, the 

 interval between d and e may be diminished to such a degree that the 

 two coincide at one point in the curve. 



The time occupied by the ventricles in relaxing (e f ) after closure 

 of the pulmonary valves is also subject to a certain degree of variation; 

 in healthy adults the average may be given as o.i second. 



When the action of the heart is greatly accelerated, the time occupied by the 

 pause is the first to become shortened, as Bonders and Landois have found; then 

 the time occupied by the auricular and ventricular systole also is shortened, in 

 lesser degree, though quite distinctly. With the highest degree of pulse-frequency 

 the beginning of the auricular systole coincides with the closure of the arterial 

 valves of the preceding heart-beat, a phenomenon that is strikingly illustrated 

 in the tracing from a dog (Fig. 28, C). 



As during the registration of apex-beat curves the heart is separated from the 

 registering instrument by the soft parts of the intercostal space, which vary in 

 thickness and in resistance and cannot in every case follow the movements of the 

 heart with entire ease, it cannot be expected that the various portions of the curve 

 shall coincide with mathematical accuracy with the corresponding phases of the 

 heart's movements. 



