Pulse Wave and the Measurement of Arterial Pressure. 351 



distended or deformed. Experimenting in the same manner with this 

 xylol-soaked tube we obtained — 



Systolic pressure. 



Obliteration pressure. 



mm. Hg. 

 133 



mm. Hg. 

 95 (fig. 5) 



Thus the rubber tube by soaking in xylol was brought to resemble the 

 artery. 



Fig. 5. 



Further experiments we have done on human arteries are these : — 

 I. We bandage the arm with a rubber bandage, place the armlet on the 

 upper arm, raise the pressure in it above systolic pressure, and then 

 remove the bandage — the arm is left exsanguined. We now place the 

 sphygmograph (using the weight extension method) in position on the 

 radial artery, then let go the armlet. We find that the pulse curve returns 

 slowly to its full amplitude when the weight extension is 300 grm., while it 

 returns almost instantaneously when the weight is 150 grm. (see fig. 6, 

 2 and 3). When the heavier weight is used the pulse wave does not lift it 

 until the tissues fill with blood and the peripheral resistance increases 

 to such a degree that the systolic pressure in the surrounding tissues and 

 artery overcomes the pressure of the sphygmograph pad which is pressing 



