(1195 ) 
We had hoped that at the moment of the Bp something similar 
would occur in the arteries and veins to what is observed at the 
moment of the M/Bp. Sometimes we suppose that from the rise and 
fall of the curve we can read something about the mbp and the 
Aw, but it appeared that this was not regularly the case. We made 
several experiments, but continued to be unsuccessful. Therefore we 
have been obliged to desist from determining the mAp and the 
mBp + Aw in this way. We only succeeded — by another method — 
to determine the bp + Aw from the plethysmographic curve. From 
what we know already about the Aw, we can, however, easily 
calculate the Bp alone. 
In order to determine the mbp + Aw we act as follows: 
After having closed the valve again we recorded once more the 
curve at 110 mm. Hg. Then every time the pressure was lowered 
5 mm. Hg, the valve of the plethysmograph was opened, shut again 
and the curve recorded. 
After fixation of the whole curve, the amplitude of the pulsation 
was measured at every observed pressure. Now it appeared that this 
amplitude gradually increased till, beginning from a definite pressure, 
it became constant, and only decreased again a little at very low 
pressure (because the armlet at that pressure fitted less tightly round 
the arm). 
We need not say that, as we were now trying to gather information 
from the amplitude of the pulse-wave, it should be registered every 
where at the same level. 
In our opinion consequently the pressure at which, operating in 
this way, we saw the pulsation show for the first time the maximal 
amplitude, is the Bp + Aw. 
To understand this we had best reverse our reasoning — as if 
from O we constantly raised the pressure. 
Thereby we must keep in view that the pulse-curve of the plethys- 
mograph is a volume-curve. 
If now the pressure in the compression-armlet is lower than the 
