AND BLOOD PRESSURE 125 



Woman Recumbent, 93 Years old. 



The writer, however, investigating the accuracy of small un- 

 enclosed sphygmometer bags, has come to the conclusion that they 

 introduce grave errors. The pressure may not be transmitted by 

 them to the artery, but go to displacing surrounding tissues, or to 

 stretching the rubber bag. The bag must be big, must be flaccid, 

 and must be entirely enclosed by a rigid casing, e.g. the hand, or 

 leather cuff of the armlet. Oliver's hsemodynamometer appears 

 to him not free from the errors which pertain to small unenclosed 

 bags. 



In seventeen out of the eighteen " diastolic" readings taken 

 with the armlet cited by Oliver, the readings are almost the same 

 (within 5 mm. Hg) on forearm and arm, or right or left arm. On 

 the other hand they exceed by 15 mm. Hg, in all except one case, 

 those taken by the hsemodynamometer. This suggests the inaccuracy 

 of the latter instrument, for the maximal pulsation index of the 

 armlet method has been tested against the blood pressure of dogs. 

 The writer has found the systolic pressure of old people may vary 

 with the different strokes of the heart, and in the young with 

 emotional excitement, and as the obliteration method gives us 

 the maximal stroke in any period, it is necessary to test the armlet 

 method by having two instruments at once on the opposite arms, 

 with two observers reading at the same time. Doing this Martin 

 Flack and the writer have found the readings taken by the ob- 

 literation method to be the same, not only in normal people but 

 in several cases of high pressure (180 to 230 mm. Hg) and of 

 thickened arteries. They have also taken the pressure with one 

 arm up and the other down, and found that the difference corre- 

 sponds to the pressure of the column of blood separating the top 

 of one armlet from the top of the other top meaning the part 

 next the shoulder. If the rigidity of the arterial wall came 



