VENOUS PULSE 59 



(at 4) of the aortic pressure, due to the rebound of the 

 aortic blood from the closed valve. During the early part 

 of the fall in ventricular pressure, the auricular pressure 

 undergoes a third rise attributed to gradual filhng. 



The Venous Pulse 



Measurement of the intracardiac pressure is a means of 

 finding out what the several chambers are doing, but it is 

 a means which from its nature can only be used upon 

 animals. We have no method of discovering the intra- 

 cardiac pressure in the human subject, but we can trace to 

 some extent the changes which are occurring in the right 

 auricle. 



ac , ac 



Jug. 



V 



Fig. 12. — Tracing of jugular pulse (from Starling's Principles of 



Physiology). 



When a tambour is pressed on the right side of the 

 neck opposite the jugular vein, and the movement trans- 

 mitted to recording apparatus, each beat is found to be 

 accompanied by three waves, known as the a, c, and v 

 waves. These are shown in Fig. 12. The a wave occurs 

 immediately after the first auricular wave, and is an expres- 

 sion of the rise in auricular pressure which is produced either 

 by the holding up of the blood in the auricle, or by the 

 regurgitation of some of the blood into the vein, the superior 

 vena cava having no valve. The c wave coincides with the 

 zenith of ventricular and aortic pressure. It depends 

 upon and is a measure of the ventricular contraction. It 

 is produced either by the transmission of the impulse from 

 the carotid artery through the tissues of the neck or by the 

 closure of the auriculo- ventricular valve. The v wave is 



