258 



ARTIFICIAL PULSE. 



[BOOK i. 



near to the peripheral resistance, with a considerable length of 

 tubing between them, and both levers be made to write on a 

 recording surface, one immediately below the other, so that their 

 curves can be more easily compared, the following facts may be 

 observed, when the pump is set to work regularly. They are 

 perhaps still better seen if a number of levers be similarly 

 arranged at different distances from the pump as in Fig. 45. 



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FIG. 45. 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.) 



