Page 145. 
8 ON POINTS CONNECTED WITH THE 
Taking the equations given in Prop. I and Prop. IT, the length of 
the systolic portion of each beat in the cardiograph- and sphygmo- 
graph-traces may be calculated with facility for any value of . From 
the equation above given, namely, zy = 20 /x and ay’ = 47 (/2, it is 
found that the length of the arterial systole is shorter than the car- 
diac, as would be expected, because the cardiograph-trace is an indica- 
tion of the movements in the muscular walls of the heart, and not of 
the contained blood, and because a certain tension must be reached by 
the intraventricular blood at the commencement of the systole before 
it can push open the aortic valves. 
The sphygmosystole being therefore shorter than the cardiac systole, 
it becomes a question, when an attempt is made to superpose them 
exactly, as to whether they correspond at the commencement or the end 
of the cardiosystole. This is easily answered; for independent obser- 
vations show the points in both at which the semilunar valves of the 
aorta close. These points in the traces must evidently be simultaneous, 
which is therefore the same thing as saying that the interval between 
the greater cardiosystole and the shorter sphygmosystole is at the 
commencement of the cardiosystole. This interval, the existence of 
which is well indicated in Marey’s cardio-aortic tracings from the 
horse, may be termed the syspasis (the time during which the ven- 
tricles are raising the pressure of their contained blood); and the 
following Table, obtained from the two equations just mentioned, 
gives its length at different pulse-rates :— 
‘0018753’ at # = 36 approximately. 
00132986’ ,, « = 49 Ks 
000931’ ,, w = 64 ns 
00004199" ;, « = 81 Xe 
0003766’ ,, « = 100 ia 
00024645’ ,, « = 121 ie 
000118’ —s,, x= 144 
000000’ Ss, # = 170 > 
From this Table it is evident that the syspasis varies considerably 
with different rapidities of pulse, decreasing rapidly with increase in 
the pulse-rate and becoming nil when it is 170 a minute, which may 
be fairly conceived to be very near the limit of cardiac rapidity in 
man. 
That this interval (the syspasis) should vary so considerably in 
length with different pulse-rates is not easy to explain at first sight; 
nevertheless a careful review of the different processes which are in 
operation in the heart at the time has suggested to me an explanation 
which seems reasonable. It depends on the fact that the extreme 
shortness of the diastole makes any variation in its length have a 
