THE PULSE. 



535 



2. The first negative wave, auricular diastole. 



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

 tricular systole. Due to sudden closure and protrusion of the au- 

 riculo ventricular valves (or to impact of the underlying arteries). 



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

 superior vena cava during a cardiac cycle in the dog : a, 6, Systole of the auricle; 6, c, d, e, 

 systole of the ventricle ; &', opening of the semilunar valves ; e, closure of the semilunar 

 valves ; 6, 6', closure of the auriculoventricular valves ; f , opening of the auriculoventricular 

 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 6 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 

 auriculoventricular 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.) 



4. Second negative wave. At the time of opening of the semi- 

 lunar valves. Due to descent of the base of the ventricle, causing 

 dilatation of auricle. 



5. Second systolic wave (positive), v wave. Latter part of 

 systole. Due to gradual filling of auricle and at the end to the 

 return of the base of the ventricle to its diastolic position. 



6. Postsystolic (third) negative wave begins at moment of 

 opening of the a-v valves. Due to emptying of auricular blood 

 into ventricle. 



Other waves have been described, especially one in the dias- 

 tolic phase of the ventricular beat, which is known as the h wave 

 (Hirschf elder) or b wave (Gibson). This wave occurs between 

 the v and the a wave and is seen most frequently and distinctly in 



