viii BLOOD-STEEAM: MOVEMENT IN VESSELS 271 



characteristics of the cardiographic and sphygmographic curves, as 

 described above, are well marked, the length in millimetres, and 

 corresponding period in fractions of a section, of the chief phases 

 of the cardiac cycle in man can easily be determined. It is well 

 to make these determinations from tracings obtained from one 

 healthy individual, with constant experimental conditions during 

 the research. The data thus obtained are of approximately absolute 

 value for the individual under observation, and are certainly far 

 more trustworthy than the average data derived from comparison 

 of results yielded by various individuals under varying experimental 

 conditions. 



From the careful measurements taken by Edgreu upon a 



Sr 



FIG. 112. Synchronous sphygrnograms of radial (X?-) and femoral (X/). (Edgren.) 



healthy man of 25, whose pulse beat 70 times per minute, the 

 following values were obtained, which may be taken as the average 

 of ten successive cardiac revolutions : 



Period of tension ... 

 Period of efflux .... 

 Total duration of systole 



Total duration of diastole . 



Total duration of cardiac revolution 



IX. If the pulse of the carotid and radial, or the carotid and 

 the femoral, or the femoral and radial are registered simultaneously 

 as shown in Figs. 110, 111, 112, it is possible to determine with 

 great accuracy the time occupied in the propagation of the primary 

 wave V, or the dicrotic wave /', by deducing it from the delay 

 between the appearance of the two waves in the arteries most 

 remote from the heart. This delay is represented in the three 

 figures by the intervals W and f'f. If they are measured with 

 a millimetre scale, it will be seen that their length alters with the 

 difference between the two arteries of which the sphygmograms are 

 compared. It will also be seen that the wave b' appears simultane- 

 ously in the femoral and the radial, while the wave f appears with 

 a measurable delay in the femoral. 



Edgren obtained the following results as the average of a 

 number of measurements of these intervals in sphygmograms taken 



