492 CIRCULATION OF BLOOD AND LYMPH. 



ular wave is due to the auricular contraction which not only forces blood 

 into the ventricle, but sends a positive wave backward into the veins. The c 

 wave is interpreted by Mackenzie as being due to the pulse of the neighboring 

 artery (carotid); while the v or ventricular wave occurs toward the end of 

 ventricular systole and is explained as being due to the abrupt checking of 

 the venous current at the time that the auricles reach their iull distension. 

 In cases of insufficiency of the tricuspid valves this wave is much increased 

 in prominence owing probably to back flow during the systole. Another 

 illustration of the venous pulse (/) is given in Fig. 206, taken from a paper 

 by Bard.* Simultaneous records are given of the carotid pulse (c) and the apex 

 beat (v), and the coincident points in the three curves are marked by the 



Fig. 206. Simultaneous tracings of the venous pulse (J), the carotid pulse (C), and 

 the apex beat of the ventricle (V). The vertical lines mark simultaneous points on the 

 three curves ; T is a time record, giving ^ sec. In the venous tracing (jugular) the following 

 waves are marked : p , caused by the contraction of the auricle (presystolic); s, the systolic 

 wave due to contraction of the ventricle ; t, telesystolic wave ; Ro, the diastole of the 

 auricle ; Rv, the diastolic expansion of the ventricle. (Bard). (See text for further de- 

 scription.) 



vertical lines. In Bard's curve of the venous pulse (J) three positive waves 

 are also shown, namely, p, s, and t, corresponding respectively to the a, c, and v 

 waves of Mackenzie. ' His interpretation, however, differs in some respect 

 from that of Mackenzie, p is a wave due to the auricular contraction, and 

 occurs, therefore, in the presystolic interval, so far as the ventricle is concerned, 

 s corresponds to the c wave of Mackenzie, but on account of the fact that it 

 occurs, as shown in the figure, before the carotid pulse and while the pressure 

 in the ventricle is rising, Bard attributes it to the sudden tightening of the 

 * Bard, "Journal de Physiologic et de Pathologic generate, " 1906, viii., 

 454 and 466. 



