224 



AKTIFICIAL PULSE. 



[Book i. 



perhaps still better seen if a number of levers be similarly 

 arranged at different distances from the pump as in Fig. 59. 



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Fir;. 59. Pulse-curves described by a series of sphygmographic levers placed at 

 intervals of 20 cm. from each other along an elastic tube, into which fluid is forced 

 by the sudden stroke of a pump. The pulse-wave is travelling from left to right, as 

 indicated by the arrows over the primary (a) and secondary (b, c) pulse-waves. The 

 dotted vertical lines drawn from the summit of the several primary waves to the 

 tuning-fork curve below, each complete vibration of which occupies ■£> sec, allow the 

 time to be measured which is taken up by the wave in passing along 20 cm. of the 

 tubing. _ The waves a' are waves reflected from the closed distal end of the tubing ; 

 this is indicated by the direction of the arrows. It will be observed that in the 

 more distant lever VI. the reflected wave, having but a slight distance to travel, 

 becomes fused with the primary wave. (From Marey.) 



At each stroke of the pump, each lever rises until it reaches 

 a maximum (Fig. 59, la, 2a, &c), and then falls again, thus 

 describing a curve. The rise is due to the expansion of the part 

 of the tube under the lever, and the fall is due to that part of the 



