204 PHYSIOLOGY CHAP. 



depressions faithfully reflect the phases of activity of the right 

 heart. 



The phlebograms made by Wenckebach present three elevations 

 and three depressions as shown in Fig. 65. 



Elevation (a) coincides with presystole, and expresses the 

 temporary arrest of the venous current (perhaps its partial reflux 

 also) during the contraction of the right auricle. The second r.ise 

 (c) corresponds with systole and depends, according to Mackenzie 

 and Wenckebach, on the mechanical transmission of the carotid 

 pulse beneath the vein that is being explored. This is rightly 



FIG. 65. Tracings of oscillations of pressure in jugular vein (phlebograms) recorded with a fairly 

 sensitive exploring tambour, applied to the base of the neck in a youth of 23, recovering 

 from catarrhal jaundice (Wenckebach). Sphygmograms from radial artery simultaneously 

 recorded with the phlebograms. Time marked in -^". The points of return marked on the 

 tracings divide the period of pulsation into the live intervals described in the text. 



contested by Fredericq, on the strength of his researches on dogs, 

 from which he proved that the rise (c) which accompanies the 

 beginning of systole is due to the closure movement of the 

 tricuspid valve. (Better expressed as, due to the projection 

 towards the auricle of the said valve, already closed at the 

 termination of presystole.) The third rise (v) coincides with the 

 tension of the semilunar valves already closed at the termination 

 of systole, and probably depends upon the impulse received by the 

 right auricle in the dilatation of the ostium and arterial bulb in 

 consequence of the wave of rebound which occurs at the com- 

 mencement of diastole. 



The depressions of the phlebograms are more interesting to 

 consider, i.e. the two negative phases of the venous pressure. The 

 first (aj), from the apex of (c) to the base of (v), coincides with 

 the phase of systolic emptying of the ventricles, and is due to 

 the sinking of the base of the ventricle by which the auricular 

 cavity becomes filled, and exercises a marked aspiration upon the 

 veins. The second negative phase (?/) coincides with diastole, and 

 depends, according to Wenckebach, on the fact that during 



