280 



VELOCITY OF PULSE WAVE. 



[BOOK i. 



by supposing that the real expansion and return of the artery at 

 any point took much less time, say Y 4 o-th sec., the length of the 

 pulse-wave would still be more than 2 meters. But even in the 

 tallest man the capillaries farthest from the heart, those in the tips 

 of the toes, are not 2 m. distant from the heart. In other words, 

 the length of the pulse-wave is much greater than the whole 

 length of the arterial system, so that the beginning of each wave 

 has become lost in the small arteries and capillaries some time 

 before the end of it has finally passed away from the beginning of 

 the aorta. 



We must now return to the consideration of certain special 

 features in the pulse, which from the indications they give or 

 suggest of the condition of the vascular system are often of great 

 interest. 



145. Secondary waves. In nearly all pulse tracings, the 

 curve of the expansion and recoil of the artery is broken by two, 

 three, or several smaller elevations and depressions : secondary 

 waves are imposed upon the fundamental or primary wave. In 

 the sphygmographic tracing from the carotid Fig. 64 and in many 

 of the other tracings given, these secondary elevations are marked 



FIG. 64. PULSE TRACING FROM CAROTID ARTERY OF HEALTHY MAN (Moens). 



x, commencement of expansion of the artery. A, summit of the first rise. 



C, dicrotic secondary wave. B, predicrotic secondary wave ; p, notch preceding this. 



D, succeeding secondary wave. The curve above is that of a tuning-fork with ten 

 double vibrations in a second. 



as B, C, D. When one such secondary elevation only is con- 

 spicuous, so that the pulse-curve presents two notable crests only, 

 the primary crest and a secondary one, the pulse is said to be 

 " dicrotic " ; when two secondary crests are prominent, the pulse is 

 often called " tricrotic " ; when several " polycrotic." As a general 

 rule, the secondary elevations appear only on the descending limb 

 of the primary wave as in most of the curves given, and the curve 

 is then spoken of as " katacrotic." Sometimes, however, the first 

 elevation or crest is not the highest but appears on the ascending 

 portion of the main curve: such a curve is spoken of as "anacrotic" 

 Fig. 65. As we have already seen ( 134) the curve of pressure 

 at the root of the aorta and indeed that of endocardiac pressure 

 may be in like manner " anacrotic " (Figs. 54, 55). 



