ioo 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. As the second positive wave is termed the ' systolic 

 rise/ this second negative wave may be designated the systolic fall of 

 venous pressure. About the end of the first third of the ventricular 



Fig. 36. Simultaneous Record of Jugular Pulse, Ventricular Contraction, Auricular 

 Contraction, and Carotid Pulse in Dog (Cushny and Grosh). a, c, v, the three 

 elevations oi the jugular pulse. Time-trace, fifths of a second. 



systole the second negative wave gives place to the third positive wave, 

 the ascent of which is rather gradual owing to the steady inflow of 

 blood into the auricle from the great veins, which gradually raises the 

 intra-auricular pressure. Towards the end the rise is accentuated by 

 the return of the base of the ventricle to the position occupied by it in 

 diastole. According to Ewing, this third positive wave, the v wave 

 of Mackenzie, really consists of two waves, the first of which he terms 

 the ' first onflow wave ' or o wave, and the second the ' diastolic rise ' 

 or d wave. This last is terminated by the third negative wave or 

 diastolic fall of venous pressure, coincident with the re -establishment of 

 a free passage for the blood from the auricle to the ventricle after the 

 relaxation of the latter and the opening of the auriculo-ventricular 

 valves. 



Some difference of opinion exists as to how the changes of pressure 

 in the auricle are propagated into the veins, although there seems to 

 be little reason to suppose that in normal persons any actual re- 

 gurgitation of blood takes place. But be this as it may, the jugular 

 curve, when properly interpreted, affords valuable information as to 



