96 PULSE RECORDS IN THEIR RELATION TO 



ventricular rhythm, the wave occurs more frequently upon the 

 jugular tracing and at equal time intervals. Experimentally it 

 has also been shown that cessation of ventricular contraction does 

 not affect it. The wave is consequently established as due to 

 auricular contraction and auricular contraction only. 



The question arises as to how it is propagated in the neck. 

 It may be supposed to result from regurgitation of blood into the 

 veins at the auricular systole. Such a view could apply only to 

 its production in the veins in the immediate neighbourhood of 

 the heart. But whether such regurgitation actually takes place is 

 by no means easy to settle. For even assuming that the right 

 auricle is supplied at the entrance of the superior vena cava with a 

 specialised band of muscular tissue, the tcenia terminalis (Keith), 

 which effectually closes the orifice by its guillotine action, yet it 

 might be supposed that a slight degree of regurgitation occurred 

 prior to the complete closure. The most direct evidence which 

 we possess is that given by Fran9ois-Franck, and this applies solely 

 to the veins of the neck. He found on fitting a Chauveau's instru- 

 ment into these veins (in the donkey and horse) that there was 

 no sign of reflux, as indicated by a retrograde movement of the 

 blood column, at any period of the cardiac cycle. 1 



Secondly, it may be attributed to a positive and centrifugal 

 wave of pressure originating in the auricle, or at the mouth of 

 the superior vena cava, and ascending the vein. Thirdly, the 

 wave may be regarded as due to the filling of the veins when the 

 outlet is obstructed ; namely, as consequent upon stasis. So far 

 as the second and third views are concerned there is little or no 

 evidence on which to base a discussion. The former tends to 

 recognise the wave as one mainly of pressure, the latter as one 

 mainly of volume. The curves obtained from the neck by means 

 of the tambour and pelotte are chiefly pressure curves, while the 

 receiving capsule, usually used, yields curves for the most part 



1 The instrument used was Chauveau's hremodromograph. Both Francois- 

 Franck and Chauveau and Faivre state that they have observed regurgitation from 

 the auricle into the roots of the great veins. But Francois-Franrk says he is con- 

 vinced that there is no reflux into the neck veins by experiments too long to report. 



The evidence for the tributaries of the inferior vena cava is even less complete. 

 There is of course every reason to suppose that it occurs in pathological conditions. 

 Experimental work on the subject is rendered very difficult, as the opening of the 

 chest which is usually necessary, produces serious alterations in the pressures of 

 the veins and right heart. 



