CIRCULATION OF THE BLOOD. sl 
In another subject, stat. 22, the following are the results :— 
Ratio borne by sphygmosystole to whole beat, as 
Pulse-rate, 
Found Caleulated 
by measurement. from radial equation. 
77 2 6625 2°595 
78 2°575 2-575 
85 2-443 2°44 . 
With regard to the posterior tibial artery, most of the results were 
obtained by the employment of the double sphygmograph, to be de- 
scribed further on, im which the superposition of the simultaneous 
posterior tibial trace on that from the radial artery showed that the 
interval between the commencing primary and dicrotic rises is the 
same in both. The following are a few independent measurements 
from tracings from the artery behind the ankle :— 
Proportion borne by first os — by 
Pulse-rate. part to whole hole ay a 
beat in ankle trace. bf in radial 
trace (approximately). 
70 2-7 2-76 
73 2°675 2-685 
80 2-596 2-525 
82 2 °4575 2-5 
82°5 2°517 2-495 
88 2°378 2-378 
Corollary.—The length of the interval between the primary and 
secondary rises being exactly the same in the carotid, radial, and pos- 
terior tibial arteries, which are three vessels at very different distances 
from the heart, it is evident that the length of this interval is constant 
throughout the larger arteries, and must be of the same duration at the 
origin of the aorta that it is in the radial artery at the wrist. 
The corollary to Prop. III leads to theoretical results of consider- Page 144. 
: able importance ; for as the duration of the different elements of each 
3 beat in the radial artery is the same as that in the commencing aorta, 
a by superposing the sphygmograph-trace upon the cardiograph-trace at 
. any given pulse-rate, a comparison can be made between the duration 
of the different physiological changes going on in the heart and those 
going on in the commencing aorta; in other words, the time during 
which the ventricular and arterial systoles are continuous can be ascer- 
tained with precision by an indirect method, which alone is possible in 
the human subject. 
G 
