too 



THE CIRCULATION OF THE BLOOD AND LYMPH 



writers, who studied it on jugular tracings, because they supposed it 

 to be simply transmitted from the pulse in the adjacent carotid artery. 

 This, however, has been shown to be erroneous, although it is true 

 enough that pulsations transmitted from the great arteries of the 

 thorax and neck may augment or distort the second elevation of the 

 venous pulse. It has been proposed that the second positive wave 

 should be called the s (systolic) wave. It lasts practically throughout 

 the presphygmic period of the ventricular systole ; the opening of the 

 semilunar valves, as indicated by the appearance of the pulse in the 

 innominate artery, occurs just before the end of the second elevation 

 (Porter, Ewing, etc.). The rapid discharge of the ventricle through the 

 open semilunar valves, and its consequent diminution in size, especially 

 in its longitudinal diameter, is associated with a dilatation of the 

 auricular cavity and a fall of intra- auricular pressure which is expressed 

 on the venous pulse -curve as the downstroke succeeding the second 

 positive wave. This second negative wave gives place to the third 

 positive wave, due to the steady inflow of blood into the auricle 

 from the veins. According to Ewing, the third positive wave, the v 



Vs \\o\o Pulse 



Fig. 36. Normal Apex and Venous Pulses, Photographically Recorded (reduced 

 nine- tenths) (Niles and Wiggers). P, presystolic (or a) wave ; S, systolic (or c) 

 wave ; D lf first diastolic (v) wave. In this venous record a second diastolic 

 wave, D 2 , is present. S 1 , vibrations corresponding to first sound ; S 2 , to second 

 sound. 



wave of Mackenzie, really consists of two waves, the " first onflow 

 wave " and the " diastolic rise " or d wave. This last is terminated by 

 the third negative wave or diastolic fall of venous pressure coincident 

 with the opening of the auriculo-ventricular valves. The re-examina- 

 tion of the venous pulse with apparatus of which the moving parts 

 have an exceedingly small mass and optical methods of recording (see 

 p. 93) has confirmed the existence on the phlebogram of three essential 

 waves. A fourth is sometimes added when the cardiac cycle is long. 

 The first wave is clearly presystolic, the second systolic, as agreed by 

 all observers who have used polygraph tracings. The third wave, 

 however, is diastolic, as is, of course, the fourth when it exists. The 

 position of these waves can be definitely fixed by simultaneous heart 

 apex tracings, since on such optically recorded cardiograms the heart- 

 sounds are represented by distinct vibrations, except where the chest 

 wall is too thick or the heart overlaid by emphysematous lung. Some- 

 times heart-sound vibrations may be present also on the record of the 

 venous pulse (Wiggers). 



