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arm, as the compression-armlet will bring about the stopping up of 
the plethysmographie apparatus towards the upper-arm. 
After this introduction we may proceed to the experiment : 
For this purpose we quickly increase the pressure in the com- 
pression-armlet, till it certainly surpasses the MBp. This must be 
done quickly in order to prevent the veins of the arm from filling 
abundantly. At a slow augmentation of the pressure in the armlet 
this would occur, as the veins are certainly sooner obliterated than 
the arteries. Therefore we must proceed rather quickly. Then the 
arteries shut themselves soon after the veins. Some veinous congestion 
certainly occurs but this is no impediment. If the pressure in the 
armlet has reached a height that doubtlessly exceeds the MBp in 
the artery, then we let simply the surplus pressure, occasioned by 
the veinous dilation of the arm, escape through a valve in the tube 
of the plethysmographic apparatus, and consequently the curve begins, 
whilst in the plethysmograph atmospheric pressure prevails. Then the 
valve is carefully closed. 
The further course of the experiment can best be demonstrated 
by following the curves. All curves have a typical form and are 
very easily registered. After some practice failures need not oecur. 
Let us take as an instance the curve obtained from J. P. V. (a normal 
individual, 26 years 17. I. 1911 Fig. U). 
We began with a pressure in the armlet of Wysauw of 160 mm. 
He. and made the drum revolve a few seconds. Neither in the 
plethysmographic curve, nor in the curve of the armlet itself any 
pulsation is seen. Consequently a pressure was reached that certainly 
surpassed the MBp. After having stopped the drum, we lowered the 
pressure to 150 mm. Hg. If we made the drum then revolve again 
for a few seconds we did not see any pulsations either, 
In this way we constantly lowered the pressure a few mm. Hg. 
and registered the curves. 
At 145 mm. Hg a feeble pulsation is observed in the curve of 
Wysauw’s armlet, in the plethysmographic curve we do not yet 
discover anything. We see the same at 140 mm. Hg. Now one must 
remark that the plethysmographic curves at 160, 150, 145 and 
140 mm. Hg are registered nearly all at the same level on the drum. 
A great change however takes place at 135 mm. Hg. Suddenly 
the plethysmographic curve goes upward. This means consequently 
that blood penetrates into the arm. For ascension of the curve means 
that the membrane of the Marry-tambour is lifted up. This means 
increase of the pressure of the air in the plethysmographic apparatus, 
and this must be the consequence of swelling of the arm. And the 
