CHARACTERISTICS OF THE RADIAL PULSE CURVE. 105 



was withdrawn from the brachial artery, but maintained in the veins. As the 

 veins till, the abscissa line of the sphygmographic curve shows a gradual rise. 

 This rise is considerable. The excursion of the wave is at the same time 

 diminished. On withdrawing the compression, as the veins empty, the pulse 

 tracing slowly returns to the normal condition. 



To the finger, the breadth or fulness of the vessels in the radial sulcus 

 appears greater during the compression of the veins, and the amplitude of the 

 excursion is diminished. On compressing the brachial artery, at the moment 

 when the elevation of the tracing produced hy compression of the veins is at 

 its maximum, the line of the trace does not fall, because the venous outlets 

 are entirely blocked (Fig. 70, tracing 2). 



TRACING 4 



TRACING 5 



Fig 70. 



Tracing 1. — A, Compression of the veins of the arm and the brachial artery ; B, com- 

 pression of the veins of the arm only ; C, compression withdrawn. 



Tracing 2. — A, Veins of the arm compressed ; the double arrow marks the height of the 

 base line before the compression was applied ; B, brachial artery occluded ; C, com- 

 pression withdrawn from the artery and veins. 



Tracing 3. — Sphygmograph resting on the femoral artery and vein of a dog. 

 vein compressed ; B, compression withdrawn. 



Tracing 4. — Sphygmograph resting on the femoral artery of the same dog. 

 vein compressed ; B, compression withdrawn. 



Tracing 5. — Sphygmograph resting on the femoral vein of the same dog. 



A, Femoral 

 A, Femoral 



A, Femoral 



vein compressed ; B, compression withdrawn. — Hill, Barnard, and Sequeira. 



In Fig. 70, tracing 3, there is recorded the effect of compressing the femoral 

 vein in the dog, while the pad of the sphygmograph rested upon the femoral 

 artery and vein. In this experiment all the other venous exits were blocked 

 by means of a ligature, which was drawn round the thigh, excluding the femoral 

 vessels. As the vein is compressed it can be seen to gradually distend, until in 

 diameter it more than equals the artery. When entirely occluded, the tension 

 within the vein rises to that of the artery. By the distension of the vein the 

 pad of the sphygmograph is elevated above the artery ; thus the line of the 

 tracing rises, while the excursion of each pulse is considerably diminished. 

 Owing to the elevation of the pad of the instrument by the vein above the 

 artery, the bottom of each curve is cut off. That the alteration of the tracing 

 is due to the rise of pressure within the vein, is shown by the next two figures. 

 In Fig. 70, tracing 4, the femoral vein was compressed, while the pad of the 

 sphygmograph rested on the femoral artery only, and in Fig. 70, tracing 5, 

 the experiment was repeated while the instrument rested on the femoral vein 

 only. 



