146 ANACROTISM. 



in the descent, but they occur very close to the apex, while the elastic 

 vibrations at the lower part of the curve are feebly marked. In 

 Fig. 61, A is from the posterior tibial, and B from the pedal artery 

 of the same individual. When measured, they give the following 



result : 



A 



12 9-5 



1-3 20 



1-4 30-5 =0-01613 sec. 



16 61 



73. Anacrotism. 



As a general rule, the line of ascent of a pulse- curve has the form of an /, and is 

 nearly vertical. The arterial walls are thrown into elastic vibration by the pulse- 

 beat, and the number of vibrations depends greatly upon the tension of the arterial 

 walls. 



The distension of the artery, or what is the same thing, the ascent of the sphyg- 

 mogram, usually occurs so rapidly that it is equal to one elastic vibration. The 

 elongated /-shape of the ascent is fundamentally just a prolonged elastic vibration. 

 When the number of vibrations causing the elastic variation is small, and when 

 the line of ascent is prolonged, two elevations occasionally occur in the line of 

 ascent. Such a condition may occur normally (Fig. 56, VIII at 1 and 2 ; X at 1 

 and 2). When a series of closely-placed elastic vibrations occur in the upper part 

 of the line of ascent, so that the apex appears dentate and forms an angle with the 

 line of ascent, then the condition becomes one of Anacrotism (Fig. 62, a, a), 

 which, when it becomes so marked, may be characterised as pathological (Landois). 

 Anacrotism of the pulse occurs when the time of the influx of the blood is longer 

 than the time occupied by an elastic vibration. Hence it takes place : 



(1.) In dilatation and hypertrophy of the left ventricle, e.g., Fig. 62, A, a tracing 

 from the radial artery of a man suffering from contracted kidney. The large 

 volume of blood expelled with each systole requires a long time to dilate the tense 

 arteries. 



(2.) When the extensibility of the arterial wall is diminished even the normal 

 amount of blood expelled from the heart at every systole requires a long time to 

 dilate the artery. This occurs in old people where the arteries tend to become 

 rigid, e.g., in atheroma. Cold also stimulates the arteries so that they become less 

 extensile. Within one hour after a tepid bath, the pulse assumes the anacrotic 

 form (Fig. 62, D) (G. v. Liebig. ) 



(3.) When the blood stagnates in consequence of great diminution in the velocity 

 of the blood-stream, as occurs in paralysed limbs, the volume of blood propelled 

 into the artery at every systole no longer produces the normal distension of the 

 arterial coats, and anacrotic notches occur (Fig. 62, B). 



(4.) After ligature of an artery, when blood slowly reaches the peripheral part 

 of the vessel through a relatively small collateral circulation, it also occurs. If 

 the brachial artery be compressed so that blood slowly reaches the radial, the 

 radial pulse may become anacrotic. It often occurs in stenosis of the aorta, as the 

 blood has difficulty in getting into the aorta (Fig. 62, C). 



Recurrent Pulse. If the radial artery be compressed at the wrist, 

 the pulse-beat reappears on the distal side of the point of pressure 

 through the arteries of the palm of the hand (Janaud, Neidert). The 



