Diastolic Waves in the Venous Pulse. 



99 



resulting from the onflowing blood, which can now no longer enter 

 the completely relaxed auricle, and must necessarily "back up" 

 into the great veins. The instant ventricular relaxation com- 

 mences, the base of the ventricle pushes up against the column of 

 blood in the auricle and veins, and thus produces a still greater 

 pressure — i. e., the diastolic rise. In all of the experiments this 

 diastolic rise has occurred synchronous with the beginning of 

 ventricular relaxation, before the closure of the semilunar valves. 

 The auricle, of course, is still passive. 



The diastolic rise continues until the ventricle has relaxed 

 sufficiently to allow the a-v valves to open, when the increased 

 pressure in the auricle is terminated by the rapid outrush of 

 blood. The resulting diastolic fall then continues until the end of 

 ventricular relaxation, or, in other words, until the ventricle 

 ceases to enlarge and receive the onflowing blood. The blood 

 which cannot enter the ventricle, "backs up" into the auricle and 

 veins, and thus produces the 2d onflow wave (Hirschfelder's "h"), 

 in a manner similar to that in which the 1st onflow wave was 

 originated. 



The reason for the non-appearance of the 1st onflow wave in 

 many jugular pulse tracings is that it is partially or completely 

 fused with the diastolic wave. (The point of separation is indi- 

 cated by a notch in many of Mackenzie's records.) The "a," "s," 

 and "d" waves are essentially impact waves, and therefore travel 

 faster than the onflow wave, which is dependent, for its rate of 

 propagation, upon the rapidity of the onflow of blood from the 

 periphery. The onflow wave appears just after the "s" wave in 

 the lower part of the sup. vena cava, but by the time the effect of 

 the "backing up" of blood has been felt in the veins of the neck, 

 the onflow wave has been overtaken and obscured by the "d" 

 wave. 



The above conclusion is supported by figures from several 

 experiments, showing that the onflow wave appeared in the jugular 

 vein .05 second later than in the vena cava. The relative positions 

 of the "a," "s, " and "d" waves do not vary in the different 

 regions. 



