136 



THE PULSE-CURVE. 



of the blood-stream. A curve (Fig. 



Fig. 56. 



Hsemautographic curve of the pos- 

 terior tibial artery of a large dog 

 P, primary pulse wave ; B, 

 dicrotic or recoil wave ; e, e, 

 elevations due to elasticity. 



56) is obtained which corresponds very closely 

 with the pulse-tracing obtained from a normal 

 artery. In addition to the primary wave, P, 

 there is a distinct " recoil-elevation, 1 ' or 

 dicrotic wave, R, and slight vibrations, e, e, 

 due to variations in the elasticity of the 

 arterial wall. The interest which attaches to 

 a curve obtained in this way is, that it shows 

 the movements to occur in the blood itself, 

 and these movements to be communicated 

 as waves to the arterial wall. By estimat- 

 ing the amount of blood in the various parts 

 of the curve we obtain a knowledge of the 

 amount of blood discharged by the divided 

 artery during the systole and diastole (i.e., 

 the narrowing and dilatation) of the artery 

 the ratio is 7:10. Thus in the unit of time, 

 during arterial dilatation rather more than 

 twice as much blood flows out as happens 

 during arterial contraction. 



Microphone. Fix a small piece of wax 

 over the radial artery, and to it attach a very 

 fine vertical wire which is brought into con- 

 tact with the charcoal of a microphone held 

 over the artery. The primary pulse wave 

 and dicrotic wave are distinctly heard in a 

 telephone brought into connection with the 

 microphone (Landois). All these methods 

 are well suited for demonstrating the pulse, 

 but for accuracy resort must be had to some 

 form of recording instrument. 



68. The Pulse-Curve or Sphygmogram, 



A sphygmogram consists of several curves, each one of which corre- 

 sponds with a beat of the heart. Each pulse-curve consists of (1.) the 

 ascending part which occurs during the dilatation (diastole) of the 

 artery; (2.) the apex, (P in Fig. 58 and I in Fig. 57); (3.) the de- 

 scending part, corresponding to the contraction (systole) of the artery. 

 The most noticeable peculiarity of the pulse-curve is the existence 

 of two completely distinct elevations occurring in the descent. The more 

 distinct of the two occurs as a well-marked elevation about the 

 middle of the descent (R, in Fig. 58 and / in Fig. 57); it is called the 

 DICROTIC WAVE, or with reference to its mode of origin, the " recoil 

 wave." The ascent, also called up-stroke or percussion stroke 

 (Mahomed), in a normal sphygmogram, is nearly vertical, while the 

 apex of the percussion stroke is usually pointed. 



[In Fig. 57, each part of the curve between the base of one up- 



