THE VENOUS PULSE. THE PHLEBOGRAM. 185 



exerted and the head is at the same time turned to the opposite side and slightly 

 upward. The pathological venous hum occurs chiefly in young anemic individuals 

 in whom also a thrill is felt over the vessel; it is present also in cases of goiter, 

 at times in youthful individuals, but it becomes less common with advancing age 



The cause of the venous hum resides in the whirling entrance of the blood 

 from the relatively narrow portion of the common jugular vein into the dilated 

 bulb situated below. It appears to be generated chiefly when the walls of the 

 thinner portion of the vein are in fairlv close apposition, so that the blood-stream 

 is obliged to force its way through. This explains the fact that the occurrence of 

 the phenomenon is favored by pressure and by turning the head to the side 

 and slightly upward. The intensity of the sound depends upon the velocity of 

 the blood as it passes through the narrow portion of the vein, and for this reason 

 the act of inspiration and the diastole of the heart, both factors accelerating the 

 venous flow, intensify the venous hum. The same is true with regard to the 

 favorable influence of the erect posture. In rare cases a sound similar to the 

 venous hum is heard in the subclavian, axillary, thyroid (in cases of goiter), facial 

 and innominate veins, the superior vena cava, the crural vein, and the inferior 

 vena cava at the blunt margin of the liver. 



Regurgitant Murmurs. The expiratory murmur heard at times in the 

 crural vein after sudden efforts at bearing-down is produced by a centrifugal 

 current of blood passing through the vein at the bend of the knee, the valves 

 being incompetent or entirely absent. When the valves in the bulb of the jugular 

 vein are incompetent, a regurgitant murmur may be produced either during 

 expiration (expiratory jugular- valve murmur) or during the systole of the heart 

 (systolic jugular- valve murmur) . In the presence of insufficiency of the tricuspid 

 valve a systolic murmur has been heard in the crural vein when its valves were 

 incompetent. 



Valvular Sounds in the Veins. Forced expiration may give rise to valvular 

 sounds in the crural vein, as the valves close with a snap under the pressure of 

 the blood forced back. In the presence of insufficiency of the tricuspid valve a 

 large quantity of blood is thrown back into the venae cavae at each ventricular 

 systole. Under such circumstances also the venous valves may close suddenly 

 with the production of a sound. The phenomenon occurs both in the bulb of the 

 jugular vein and in the crural vein at the bend of the knee, but only when the 

 respective valves are competent. 



THE VENOUS PULSE. THE PHLEBOGRAM. 



Method. If the movements of a vein are recorded by means of a lightly 

 weighted sphygmograph a heavy load would compress the vein or at least 

 obliterate the delicate details of the curve a characteristic form will be observed 

 in a successful venous pulse-curve or phlebogram (Fig. 72). 



In the proper interpretation of the details of the phlebogram it is especially 

 important to determine its chronological relations to the phases of the heart's 

 action; hence, it is advisable to record a cardiogram and a phlebogram simulta- 

 neously (on a recording surface attached to a vibrating tuning-fork) . The begin- 

 ning of the carotid pulse coincides approximately with the apex of the cardiogram, 

 that is to say, with the descending limb of the phlebogram. 



The venous pulse within the common jugular vein is a normal phenomenon. 

 A pulsating movement synchronous with the movements of the heart is frequently 

 observed in the course of this vein. (Compare Fig. 34.) The movement may 

 extend only to the lower portion of the vein, the so-called bulb, or higher up to 

 the trunk of the vein itself. When the valves of the common jugular vein above 

 the bulb are incompetent, a condition that is not at all rare, even in healthy per- 

 sons, the phenomenon is particularly marked. The undulating movement ad- 

 vances from below upward; as a rule, it is observed only when the subject lies 

 quietly in the horizontal position; it is more common on the right than on the 

 left side, because the course of the right vein is straight and the vessel is nearer 

 the heart than the left vein. The movement is propagated more slowly than the 

 arterial pulse-wave. 



The venous pulse possesses the peculiarities of the movement of the heart. The 

 tracing exhibits in a marked degree all of the details of tin- a] u-x-bcat curve, especially 

 in connection with the pathological conditions to be discussed presently, and it there- 

 fore closely resembles such a curve, as is shown beyond a doubt by a comparison 

 of the venous pulse-curve (Fig. 72, i) with the apex-beat curve (Fig. 28, A). 



