THE PULSE. 529 



One view of the relation of the different venous waves to the 

 sequence of events in the ventricle and aorta is shown in the 

 diagram given by Fredericq, which is reproduced in Fig. 219. 

 Following this author,* the series of positive and negative waves 

 which usually occur in the auricles and great veins during a 

 single heart beat may be enumerated as follows: 



1. The am-icular wave (a wave), auricular systole. 



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). 



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 h wave (Gibson). This wave occurs between 

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

 the case of hearts with a slow rate of beat. The usual explanation 

 of this wave is that it is due to the very sudden distention of the 

 ventricles by the inflowing blood. The rise in intraventricular 

 pressure thus produced brings the auriculoventricular valves 

 suddenly into a position of closure and causes a momentary posi- 

 tive wave in the auricles and great veins. For the variations in 

 the form of the venous pulse under pathological conditions of the 

 heart, reference must be made to clinical literature.* 



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

 *See Hewlett, "Journal of Medical Kesearcu, ' 17, 1907; "Journal of 

 the Amer. Med. Assoc," 51, 1908, and Hirschfelder, "Diseases of the 

 Heart and Aorta," Philadelphia, 1910. 

 34 



