246 ANIMAL PHYSIOLOGY. 
children with their more elastic arteries the speed is slower; 
and the same principle is supposed to explain the higher veloci- 
Fig. 216.—Pulse-curves described by a series of sphygmographic levers placed 20 cm. apart 
along an elastic tube into which fluid is forced by the sudden stroke of a pump. The 
arrows indicate the onward and the reflected waves. The gradual flattening and total or 
partial extinction of the waves are noteworthy (after Marey). 
ty noticed in the arteries of the lower extremities. But with 
such a speed as even five metres a second it is evident that with 
a systole of moderate duration (say °3 second) the most distant 
arteriole will have been reached by the pulse-wave before that 
systole is completed. 
It is known that the blood-current at its swiftest. has no 
such speed as this, never perhaps exceeding in man half a metre 
per second, so that the pulse and the blood-current must be two 
totally distinct things. 
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