140 DICROTIO PULSE. 



vibratory movements when it passes suddenly from the distended to 

 the relaxed condition. These small elevations in the pulse-curve, 

 caused by the elastic vibrations of the arterial wall, are called " elastic 

 elevations " by Landois. 



(1.) The elastic vibrations increase in number in one and the same 

 artery with the degree of tension of the elastic arterial wall. A very 

 high tension occurs in the cold stage of intermittent fever, in which 

 case these elevations are well marked. (2.) If the tension of the 

 arterial wall be greatly diminished these elevations may disappear, 

 so that while diminished tension favours the production of the dicrotic 

 wave, it acts in the opposite way with reference to the " elastic 

 elevations." (3.) In diseases of the arterial walls affecting their 

 elasticity, these elevations are either greatly diminished or entirely 

 abolished. (4.) The farther the arteries are distant from the heart, 

 the higher are their elevations. (5.) When the mean pressure within 

 the arteries is increased by preventing the outflow of blood from 

 them, the elastic vibrations are higher and nearer the apex of the 

 curve. (6.) They vary 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-vessela 

 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. 58, X), 



Fig. 59. 

 Pulsus dicrotus P. caprizans ; P. monocrotus. ' 



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 



