964 



PHYSIOLOGY 



If the end o of the tube is closed, the wave of a positive pressure on 

 arriving at B will be reflected back as a positive reflected wave. If a 

 tracing be taken of the oscillations or variations of pressure in the tube, 

 two waves at least are seen) one of which is the primary wave due to the 



Fid. 420. 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. Th? pulse valve is travelling from 

 loft to right, as indicated by the arrows over the primary (a) and secondary 

 (6, 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 7 ,' () 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 lover (VI) the reflected 

 wave, having but a slight distance to travel, becomes fused with the primary 

 vrave, so that the rise of pressure in VI is actually greater than that in V. 

 (From FOSTER, after MAREY.) 



movement of fluid caused by the piston ; the other is the secondary wave 

 reflected back from the periphery. The fact that the secondary wave is 

 a reflected one is shown by the fact that the nearer to the peripheral resist- 

 ance the pulse is recorded, the nearer is the secondary to the primary wave, 

 as is seen in Fig. 420. 



