POLYSPHYGMOGRAMS 287 



stroke be made through the point obtained by this measurement it 

 will be found to cut the venous curve at the beginning of a small wave 

 (c) which is produced by the bulging into the auricles of the closed au- 

 riculo-ventricular valves. Our measurements show that this "c" wave 

 of the venous tracing commences at the same instant that the upstroke 

 appears in the carotid tracing. That these events are simultaneous in 

 the respective curves may be shown in another way, for example, should 

 two such tracings be separated (by dividing the paper longitudinally 

 between them) and superimposed, so that their respective alignment 

 marks lay in the same straight line, we would find that line 3 drawn 

 from the upstroke of the carotid tracing would when continued through 

 the venous curve intersect the latter at the commencement of the "c" 

 wave. We would then have an arrangement identical with that of the 

 venous and carotid tracings in Fig. 95. 



The auricular wave (a) of the venous pulse, which is due to the sys- 

 tole of the auricle, is determined by measuring approximately one-fifth 

 of a second in front of the "c" wave. Line 1 passes through the com- 

 mencement of this wave. In order to identify other waves in the venous 

 tracing similar procedures are carried out as in the case of the "c" 

 wave determination. If the distance from the alignment mark of the 

 carotid tracing to the commencement of the dicrotic notch of the latter 

 be measured and the same distance marked off on the venous tracing, a. 

 line drawn through the point so obtained will be found to fall upon 

 the upstroke of a large wave "v" close to its summit. In a similar 

 manner a measurement of the carotid curve from its alignment mark to 

 the termination of its dicrotic wave (intersection of line 6) would, 

 when transposed to the venous pulse tracing, indicate a point on the 

 down slope of "v" a short distance beyond its summit. 



As the time consumed in the propagation of the pulse to the jugular 

 and to the carotid is approximately the same in either case, the carotid 

 tracing, in order to avoid confusion, has been used as the standard for 

 comparison in the foregoing calculations; but the radial curve is more 

 commonly employed for this purpose. When such is the case the time 

 required for the propagation of the pulse from the neck to the wrist 

 must be taken into our calculations. This is about one-tenth second, so 

 that when the radial tracing is employed we must measure to a point 

 one-tenth second in front of its upstroke (or dicrotic wave) and apply 

 this distance to the venous tracing in order to obtain synchronous points 

 in the two curves. 



The respective factors responsible for the production of the "c" and 

 "a" waves have already been mentioned, the production of the other 

 features of the venous pulse tracing remains for consideration. The de- 



