528 



CIRCULATION OF BLOOD AND LYMPH. 



down of the floor of the auricle would tend to lower intra-auricular 

 pressure, and the negative wave thus produced if transmitted back 

 to the jugular vein would coincide in time with the fall in pressure 

 following the c wave. This negative wave is converted into a posi- 

 tive wave by the steady inflow of venous blood, which continues to 



Fig. 219. — Schema of the variations or pressure in the ventricle, auricle, aorta, ano 

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

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

 valves ; b, b', 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 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 

 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.) 



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, there- 

 fore, of the base of the ventricle to its diastolic position. Im- 

 mediately 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. 



