THE PULSE. 



531 



therefore, of the base of the ventricle to its diastolic position. 

 Immediately afterward the auriculoventricular valves open, 

 and the blood accumulated in the auricles is discharged into 

 the ventricle, causing again a sudden fall of pressure in the 

 auricles and veins, the third negative wave. 



The true relations of these different venous waves to the 

 sequence of events in the ventricle and aorta are clearly shown 



Fig. 219. Schema of the variations of pressure in the ventricle, auricle, aorta, and 



VOMWB | v.v | ^IVJOLIIC *JA tuc: aumjuiuv ciitnuuitu va.ivcs , /, opening ui tiie ituricuiuv enincujar 

 valves. ^ On the curve for the auricle and vein the wave from a to 6 represents the auricular 

 contraction, the a wave; that beginning at b is the wave due to ventricular systole, the 

 c wave, and the rise of pressure extending from d to e and ending with the opening of the 

 auriculoyentriciilar valves constitutes the v wave. The time relations are given along the 

 abscissa in tenths of a second, the pressure relations in mms. of mercury for the ventricle 

 and aorta are given along the ordinates to the left. (After Fredericq.) 



in the diagram given by Frederic q, which is reproduced in Fig. 

 219. Following this author,* the series of positive and negative 

 waves which may usually be shown in the auricles and great 

 veins during a single heart beat may be enumerated as follows: 



1. The auricular wave (a wave), auricular systole. 



2. The first negative wave, auricular diastole. 



3. First systolic wave (positive), c wave. Beginning of 

 ventricular systole. Due to sudden closure and protrusion of 

 the auriculoventricular valves. 



* Fredericq, " Centralblatt f. Physiol.," 22, No. 10, 1908. 



