ANAL YSIS OF PULSE CUR VE. 



Such results as these have been obtained : — 



109 



If this be so, it is argued, the dicrotic wave must either be modified, 

 or produced, by waves reflected from the periphery. On the other 

 hand, this difference in velocity time may be due simply to differences 

 in arterial pressure, which may exist at the period of the dicrotic wave. 

 The greater the tension of the arterial wall, the greater is the velocity. 

 No doubt reflected waves may be produced in such a system of branching 

 tubes as the arteries form. Such reflected waves must arise at different 

 distances from the heart, spread into every branch of the system, and 

 modify, not only each other, but the primary waves by interference, 



Fig. 74. — Experiment to show central origin of dicrotic wave. — Grashey. 



v. Kries bled an animal to death, placed a spring manometer in 

 connection with the femoral artery, and a bag tilled with fluid in connec- 

 tion with the aorta. 1 This bag was suddenly compressed, and retained 

 in the compressed position. Thus a primary positive centrifugal wave 

 was propagated through the arterial system. This gave rise to secondary 

 waves, which v. Kries attributed to reflection. On the other hand, it 

 must be borne in mind that these waves were obtained under the most 

 favourable conditions, and it is very doubtful whether such waves would 

 be visible when produced under the conditions of the ordinary pulse 

 curve. Moreover, the waves may have been occasioned rather by 

 oscillations of the wall of the aorta, than by reflections from the 

 periphery. 



In order to demonstrate the central origin of the dicrotic wave, Grashey 2 



1 v. Kries, "Studien zur Pulslehre," S. 62, cf. v. Frey, "Die Untersuch. des Tulses," 

 S. 164. 



2 "Die Wellenbewegung elasticher Riihren," Leipzig, 1881, S. 165. 



