530 CIRCULATION OF BLOOD AND LYMPH. 



somewhat into the auricle and thus cause a positive wave in the 

 venous blood which is propagated back into the large veins. 

 Immediately upon the opening of the semilunar valves blood 

 streams out of the ventricle into the pulmonary artery, and the 

 ventricle diminishes rapidly in size especially in the diameter 

 from base to apex. This sudden descent of the base of the 

 ventricle pulls downward the floor of the auricle and causes a 

 sudden enlargement of the auricular cavity, which in turn 

 produces a temporary negative pressure in the auricle and 



Fig. 218. Simultaneous tracings of the jugular pulse, the carotid pulse, and the 

 apex beat. (Bachmann.) At the bottom of the tracing the time is given in fiftieths of 

 a second. The vertical lines 0, 1, 2, 3, etc., mark synchronous points on the curves. 

 A, The auricular wave; s, the so-called c wave caxised by the systole of the ventricle; v, the 

 stagnation wave caused by the filling of the auricle. It will be noticed that the c wave 

 (marked s in the tracing) occurs at the beginning of the ventricular systole as marked on 

 the apex beat, and shortly before the pulse in the carotid artery. The height of the v wave 

 is reached just after the occurrence of the dicrotic notch on the carotid wave, and coin- 

 cides with the opening of the auriculoventricular valves; Af, the negative wave caused by 

 the effect of the ventricular systole; Vf, the negative wave following the opening of the 

 auriculoventricular valve?. 



attached veins. The second negative wave is, therefore, due to 

 a forcible dilation of the auricle caused by the systole of the 

 ventricle. This negative wave is converted into a positive wave 

 by the steady inflow of venous blood, which continues to pour 

 into the auricle during the whole period of the systole of the 

 ventricle and of the closure of the auriculoventricular valves. 

 In this way the wave v is produced. It is frequently of irregular 

 or toothed form and rises somewhat gradually to its maximum. 

 The end or maximum of the wave falls in with the beginning 

 of the muscular relaxation of the ventricle, and the return, 



