230 



VELOCITY OF PULSE WAVE. 



[BOOK i. 



estimate, by supposing that the real expansion and return of the 

 artery at any point took much less time, say yftth 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. 



127. 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 jmposed upon the fundamental or primary wave. In 

 the sphygmographic tracing from the carotid, Fig. 63, and in many 

 of the other tracings given, these secondary elevations are marked 



FIG. 63. 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 conspic- 

 uous, 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, " poly erotic." 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. 64. As we have already seen ( 116) the curve of pressure 

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

 may be in like manner " anacrotic " (Figs. 53, 54). 



