CHARACTERS OF THE PULSE. 141 



in a normal pulse. The sensible second beat is nothing more than 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 a 

 diminished tension within the arterial system. A short systole and diminished 

 arterial blood-pressure are the most favourable conditions for causing a dicrotic 

 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 the 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 compressing 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 40C.), whereby the artery is more dis- 

 tended, and the heart-beat is shorter and more prompt (Riegel). 



(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 

 (Landois). In Fig. 59, A, B, C, we observe the gradual passage of the normal 

 radial curve, A, into the dicrotic beat, B, C, where the dicrotic wave, r, appears 

 as an independent 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, G (P. 

 caprizans). If the next following beat occurs in the depression, i, between the 

 primary elevation, p, and the dicrotic elevation, r, the latter entirely dis- 

 appears, and the curves, H, assume what Landois calls the " monocrotic " type. 



70. Characters of the Pulse. 



1. Pulsus Frequens and Rarus. 



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 rare. 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 (cle Haen), 17 (Hartog), and 14 (Cornil) ; but such 

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

 frequency of the pulse is usually increased when the respirations are deeper, but 

 not more numerous, i.e., rapid shallow respirations do not affect the frequency of 

 the pulse, but deep respirations do (Knoll). 



2. Pulsus Celer and Tardus. 



Celerity or Rapidity. If the pulse-wave is developed so that the distension of 

 the artery slowly reaches its height and the relaxation also takes place gradually, 

 we have the p. tardus or slow pulse, the opposite condition gives rise to the p. 

 celer or quick pulse. The rapidity of the pulse is increased by quick action of the 

 heart, power of expansion of the arterial walls, easy efflux of blood owing to the 

 dilatation of the small arteries, and by nearness to the heart. [The quickness 

 has reference to -a single pulse-beat, the frequency to a number of beats.] In a 

 quick pulse, the curve is high and the angle at the apex is acute, while in a slow 

 pulse the ascent is low and the angle at the apex is large. 



