The Resonance of the Tissues. 



265 



slowly, to normal or above normal. This is the important point, that the 

 blood-pressure reading in the radial artery rises much more slowly in the cold 

 ischemic limb wherein the arteries are constricted than in the warm ischemic 

 limb wherein the arteries are dilated. At the conclusion of the experiment, 

 when the blood pressure is back to normal, the aberrant radial artery still 

 feels like a whipcord — highly contracted. Massage of the whipcord artery will 

 bring it back to the worm-like condition which obtained in the congested 

 limb. 



Accordingly we can conclude that the phenomenon occurs in the dilated or 

 in the contracted artery — it is immaterial which. Consequently the initial 

 low blood pressures (as measured by the disappearance of pulse) on allowing 

 the blood to enter the arteries are independent of the state of the arterial 

 wall. They are also independent of the peripheral resistance. 



Blood-pressure estimations were made on the aberrant radial artery at the 

 close of these experiments on the warm limb (now congested) and on the 

 ■cold limb. 



When the systolic pressure had arisen to the normal 120-130 mm. of Elg- 

 in the forearm in the warm limb the reading obtained at position I on the 

 dilated aberrant radial artery was 50-60 mm. of Hg. In the cold limb when 

 the blood-pressure reading in the forearm was found to be 150-160 mm. of 

 Hg (the same as the initial pressure in the individual tested), the constricted 

 aberrant radial artery gave a reading of 70-80 mm. of Hg. 



We conclude, therefore, that the pulse in either the dilated artery or the 

 contracted artery can be damped down by a pressure 70-80 mm. Hg or so 

 below normal. Experiments similar to the above, and with like result, can 

 be performed on the dorsalis pedis artery. 



We have traced in the ischemic limb the rise in the size of the beat of the 

 radial artery, or of the dorsalis pedis artery, or of the aberrant radial artery 

 (at position I) using both Mackenzie's polygraph and the weight-extension 

 method and the Dudgeon sphygmograpb, and blocking the artery below to 

 prevent the recurrent pulse. When the armlet is compressed in the upper 

 arm and the pressure suddenly let go, one notes that the beat in the congested 

 limb returns quicker to its normal size than in the ischaeniic limb. In all 

 -cases the beat takes longer to come to normal when the weight-extension 

 Dudgeon is used than when the tracings are taken by the polygraph. The 

 weight-extension method of applying the Dudgeon avoids the plethysmo- 

 graphic effect of the polygraph (Lewis). One often finds the pulse takes 

 a minute to return to its maximal swing, i.e. until the surrounding tissues are 

 filled with blood and resonate with it. 



It might be argued in the light of the fact that the return of the maximal 



