262 Messrs. L. Hill, J. M. McQueen, and W. W. Ingram. 



Table where Supporting Pressure is Applied as far as possible Simultaneously 



at Elbow and Forearm. 



Supporting pressure of armlet 

 applied at position III and part 

 of II. 



Supporting pressure of 

 sphygmometer bag 

 at position IV. 



Sphygmometer bag at part of 

 position I and part of II. 



Increase in mm. of Hg on 

 ^previous reading before 

 application of supporting pres- 

 sure at elbow and forearm. 



mm. of Hg. 

 Experiment I ... 20 

 Experiment II . . . 30 

 Experiment III ... 40 

 Experiment IV ... 50 



mm. 

 20 

 30 

 40 

 50 



Note. — Care must be taken 

 that the bag at IV is 

 applied as in Diagram 

 III a. 



5-10 

 5-10 

 5-10 

 5-10 



Note. — It is not possible to apply these pressures at Positions IV, III and part of II with 

 perfect synchronism, as the pressure cannot be raised in the armlet to 50 mm. without two 

 compressions of the pump. 



Accordingly, provided one guards against errors from change in the arterial 

 wall through manipulation — we have noted that after many readings with the 

 bag at position I the artery becomes obviously harder and the reading rises — 

 and, provided one constantly guards against a rise in arterial pressure during 

 an experiment, then lack of support of the wall may account for a loss of 

 pressure of 5-10-15 mm. of Hg. But such lack is obviously unable to account 

 for the low reading at position I of 50-60 mm. of Hg. Further, the experi- 

 mental observations with the sphygmometer bag on varying positions at IV 

 show that the main factor must be the resonance of the tissues. 



But low readings with the sphygmometer bag are not confined to aberrant 

 radial arteries. Thus one may observe the same phenomenon on the dorsalis 

 pedis artery. 



Beading with bag on dorsalis pedis horizontal position — 



mm. Hg. mm. Hg. 



Dorsalis pulse disappears 85. Bight radial pulse disappears 145. 

 „ „ reappears 80 „ „ „ reappears 140. 



In this case the dorsalis pedis available was short and the foot was fleshy. 

 In another case where the dorsalis pedis is longer and the tissues sur- 

 rounding it scantier, then — 



