384 THE MECHANICS OF THE CIRCULATION, HEMODYNAMICS 



(A-B) is generally smooth; its steepness, however, varies with the 

 tension prevailing in the arteries. If the pressure is high, the ascent 

 must be slower, because it is then developed against a greater resist- 

 ance. A low pressure, on the other hand, favors a more rapid rise in 

 pressure and hence, also the production of a more vertical anacrotic 

 limb. It should also be remembered that if the resistance in the arterial 

 system is high, the upstroke frequently shows certain secondary waves 

 which indicate the occurrence of an elastic quivering. Conditions of 

 this kind are encountered in arteriosclerosis and stenosis of the semi- 

 lunar valves. These extra oscillations which are generally situated 

 near the apex of the curve, are known as anacrotic waves. In accord- 

 ance with the preceding statement, it may be assumed that they are 

 tension- waves, i.e., quick reflections from the periphery. This view 

 was first expressed by v. Kries, ^ who produced them in the radial artery 

 by raising the hand to such a level that the static effects permitted the 

 occurrence of reflections from the periphery before the summit of the 

 pulse-curve had been reached. Obviously, any condition which hin- 

 ders the quick emptying of the ventricles, must give sufficient time for 

 these reflections to develop. They are especially prone to occur in 

 aortic stenosis when the narrowing of the aortic orifice is associated 

 with a hypertrophy of the ventricular musculature. 



The apex (B) of the normal pulse-wave possesses a rounded out- 

 line, while in the sphygmogram it is generally very pointed. This 

 discrepancy must be attributed to an instrumental error, namely, to 

 the ''fling" which is imparted to the lever and its connecting parts 

 whenever the artery is suddenly expanded. When especially conspicu- 

 ous it is called the "percussion-wave.'^ 



The catacrotic limb (B-C) exhibits several details which deserve 

 a more lengthy discussion. Its most constant characteristic is a 

 well-marked secondary rise which appears near the middle of the de- 

 scent and is known as the dicrotic wave (D) . Subsequent to this point 

 a number of smaller wavelets are usually observed which are desig- 

 nated as the postdicrotic waves (F). Immediately preceding the di- 

 crotic wave, a small oscillation is generally obtained which is called 

 the predicrotic wave (E). Between points E and F, the curve shows 

 a depression, known as the dicrotic notch (n). 



While the dicrotic character of the pulse was recognized by pal- 

 pation long before the invention of the sphygmograph, its dicrotism 

 was first demonstrated in a plastic manner by Thelius in 1850.^ Some- 

 time later Marey^ obtained graphic records of it, while Landois* 

 proved its existence by pricking an artery with a needle and by permit- 

 ting the blood to spurt against the paper of a slowly revolving 

 kymograph. Records of this kind are called hematograms. 



1 Studien zur Pulslehre, 1892. 



^ Vierteljahrschr. fiir prakt. Heilkunde, xxi, 1850. 



3 Jour, de la Physiol., iii, 1860. 



* Pfluger's Archiv, ix, 1874. 



