274 



THE CIRCULATION OF THE BLOOD 



The auricular wave (a) occurs one-fifth of a second in front of c, and 

 may now be ascertained by measuring off this distance in front of c. 

 This is line 1. 



Now measure the distance on the radial pulse tracing from the begin- 

 ning of the upstroke to the dicrotic notch. The distance between these is 

 the sphygmic period (E). 



Fig. 95. Polysphygmograph. This instrument records in ink on glazed paper two simul- 

 taneous tracings, i. e., radial pulse and one other, such as carotid, jugular, apex beat, etc., in addi- 

 tion to the time tracing. The ink tracings are both more convenient and permanent than smoked 

 paper tracings. The clockwork operates at variable speeds, permitting the taking of protracted 

 records at different speeds. 



Measure off the same distance on the venous tracing from c. Line 

 5 will be found to fall just before a small wave (v), which is due to the 

 sudden opening of the tricuspid valves. This practically coincides with 

 the dicrotic notch on the radial pulse tracing. Sometimes a little wave 



Fig. 96. Normal jugular tracing. The spacing below shows the duration of the a-c interval. 



(From E. P. Carter.) 



occurs on the upstroke of wave v just where line 5 falls. This co- 

 incides with the closure of the semilunar valves. The distance between it 

 and wave v corresponds to the postsphygmic period. 



The cause for the depression (marked x) following c will readily be 

 understood by referring to the intraauricular curve (Fig. 97), to which, 

 as already explained, the venous pulse tracing is qualitatively similar. 



