THE CIRCULATION OF THE BLOOD. 945 
If water be sent through a long elastic tube (so coiled that 
points near and remote may be felt at the same time) by a bulb 
syringe, imitating the heart, and against a resistance made by 
drawing out a glass tube to a fine point and inserting it into 
the terminal end of the rubber tube, an intermittent pressure 
like that occurring in the artery may be observed; and further 
Ng | 
in 
iat 
Fic. 215.—Marey’s apparatus for showing the mode in which the pulse is Brepagated in the 
arteries. B,a rubber pump, with valves to prevent regurgitation. The working of the 
apparatus will be apparent from the inspection of the figure. ‘ 
that it does not occur at precisely the same moment at the two 
points tested. 
Information more exact, though possibly open to error, may 
be obtained by the use of more elaborate apparatus, and the 
graphic method. 
Fig. 216 gives an idea of the main features of the pulse-trac- 
ings of an arterial scheme or arrangement of tubes in supposed 
imitation of the conditions existing in the vascular system of 
the mammalian body. Attention is especially directed to the 
abrupt ascent, the more gradual descent, and the secondary 
waves, which are either waves of oscillation or reflex waves. 
It may also be noticed that the rise is later as the part of 
the tube at which it occurs is more distant from the pump; 
also that it gets gradually less in height and at the same time 
that all the secondary waves are diminished or totally disap- 
pear; and with the exception of the latter these results hold 
good of the pulse in the arteries of a living animal. 
By measurement it has been ascertained that in man the 
pulse-wave travels at the rate of from five to ten metres per sec- 
ond, being of course very variable in velocity. It would seem 
that the more rigid the arteries the more rapid the rate, for in 
