THE CIRCULATION OF THE BLOOD. 359 



It is caused by variations of pressure transmitted backward into the veins 

 during and after the systole of the auricle. Though the venous pulsation is 

 not very marked in physiologic conditions it frequently becomes pronounced 

 in certain pathologic conditions of the heart. 



The pressure variations in the jugular vein can be recorded by applying 

 over the vein a properly constructed tambour, a glass funnel or a Mackenzie 

 metal tambour connected with a suitable recording tambour. A graphic 

 record of a normal venous pulse thus obtained, shown in Fig. 171, is rather 

 complicated, consisting of three positive and three negative waves which 

 are related to variations of pressure in the right auricle, the result of the 

 successive contractions of the auricular and ventricular walls and the action 

 of intra-ventricular structures. 



FIG. 171. SIMULTANEOUS TRACINGS OF THE JUGULAR PULSE, THE CAROTID PULSE, AND THE 

 APEX BEAT. (Bachmann.} At the bottom of the tracing the time is given in the fiftieths of a 

 second. The vertical lines o, i, 2, 3, etc., mark synchronous points on the curves. A, The 

 auricular wave; s, the so-called c wave caused by the systole of the ventricle; v, the stagnation wave 

 caused by the filling of the auricle. It will be noticed that the c wave (marked 5 in the tracing) 

 occurs at the beginning of the ventricular systole as marked on the apex beat, and shortly before 

 the pulse in the carotid artery. The height of the v wave is reached just after the occurrence of 

 the dicrotic notch on the carotid wave, and coincides with the opening of the auriculoventricular 

 valves; Af, the negative wave caused by the effect of the ventricular systole; Vf, the negative wave 

 following the opening of the auriculoventricular valves. 



As the venous pulse is a very evident symptom in some pathologic condi- 

 tions of the heart, and as its proper interpretation assists in the diagnosis of 

 these conditions, it has become of much significance in modern clinical medi- 

 cine. For purposes of interpretation it is desirable to obtain simultaneously 

 graphic records not only of the venous pulse, but of the carotid or radial 

 pulse, and of the cardiac impulse as well. In the accompanying figure 171 

 these three records are represented. 



The generally accepted interpretation of these waves is as follows : 

 The first positive wave, a, is due to an expansion of the vein, the result 

 of a sudden rise of pressure. As it occurs before the ventricular systole, it 

 is pre-systolic in time and caused by the contraction of the auricle, the 



