io6 



DICROTIC PULSE. 



in number and length in the pulse-curves obtained from different arteries of the 

 body. 



When the arm is held in an upright position, after five minutes the blood-vessels empty 

 themselves, and collapse, while the elasticity of the arteries is diminished. 



69. Dicrotic Pulse. Sometimes during fever, especially when the temperature is high, a 

 dicrotic pulse may be felt, each pulse-beat, as it were, being composed of two beats (fig. 83, X), 

 one beat being large and the other small, and more like an after-beat. Both beats correspond 

 to one beat of the heart. The two beats are quite distinguishable by the touch. The 

 phenomenon is only an exaggerated condition of what occurs in a normal pulse. The aenribk 



Fig. 86. 

 Development of the Pulsus dicrotus P. caprizans ; P. monocrotic. 



second beat is nothing more limn the greatly increased dicrotic elevation, which, under ordinary 

 conditions, is not felt by the finger. 



Conditions. The occurrence of a dicrotic pulse is favoured (1) by a short primary pulse* 

 wave, as in fevers, where the heart beats rapidly. 



(2) By diminished arterial tension. A short systole and diminished arterial blood-pressure are 

 the most favourable conditions for causing a dicrotic pulse. [So that dicrotism is best marked 

 in a soft pulse.] The double beat may be felt only at certain parts of the arterial system, 

 whilst at other parts only a single beat is felt. A favourite site is the radial artery of one or 

 other side, where conditions favourable to its occurrence appear to exist. This seems to be due 

 to a local diminution of the blood-pressure in this area, owing to the paralysis of its vaso- 

 motor nerves (Landois). If the tension be increased by compresisng other large arterial trunks 

 or the veins of the part, the double beat becomes a simple pulse-beat. The dicrotic pulse in 

 fever seems to be due to the increased temperature (39 to 40 C. ), whereby the artery is more 

 distended, and the heart-beat is shorter and more prompt. 



(3) It is absolutely necessary that the elasticity of the arterial wall be normal. The dicrotic 

 pulse does not occur in old persons with atheromatous arteries. 



Monocrotic Pulse. In fig. 86, A, B, C, we observe a gradual passage of the normal radial 

 curve, A, into the dicrotic beat, B, and C, where the dicrotic wave, r, appears as an indepen- 

 dent elevation. If the frequency of the pulse increases more and more in fever, the next 

 following pulse-beat may occur in the ascending part of the dicrotic wave, D, E, F, and it may 

 even occur close to the apex, (i (P. caprizans). If the next following beat occurs in the 



depression, i, between the primary 

 elevation, p, and the dicrotic eleva- 

 tion, r, the latter entirely disappears, 

 and the curve, H, assumes what Lan- 

 dois calls the "monocrotic" type. 



[Degrees of Dicrotism. When the 

 aortic notch reaches the respiratory or 

 base line, the tidal wave having dis- 

 appeared, the pulse is said to be fully 

 dicrotic. When the aortic notch falls below the base line, i.e., below where the up-stroke 

 begins, the pulse is said to be hyperdicrotic (fig. 87). This form occurs during high fever (104 

 F.), and is usually a grave sign, indicating exhaustion and the need for stimulants.] 



70- CHARACTERS OF THE PULSE. [The three factors concerned in the production of 

 the pulse are, (1) the action of the heart, (2) the elasticity of the large vessels, (3) the resistance 

 in the small arteries and capillaries. Any or all or several of these factors may be modified.} 

 (1) Frequency. According as a greater or less number of beats occurs in a given time, e.g., 

 per minute, the pulse is said to be frequent or infrequent. The normal rate, in man = 71 

 per minute, and somewhat more in the female ; in fever it may exceed 120 (250 have been 

 counted by Bowles), while in other diseases it may fall to 40, and even 10 to 15 ; but such 

 cases are rare, and are probably due to an affection of the cardiac nerves ( 41). The frequency 



Fig. 87. 

 Hyperdicrotic pulse. 



