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whilst ouly the distal chamber is connected with the registering- 
apparatus (according to ERLANGER’s principle) and registers the pulsations 
of the encircled artery. With our method we have consequently, at 
the same time, registered the curve that depends on the principle 
of the greatest oscillations. Occasionally we have used the narrow 
compression-armlet of Riva-Rocci and then we have not registered 
the oscillations. 
We wrote consequently above each other: I the curve according 
to the oscillatory method, 2 the curve of the plethysmograph. Only 
the pressure prevailing every time in the armlet was read on the 
manometer and always immediately registered in the curve. 
In order to obtain fine curves, it is advisable to make the patient 
hold his breath for a few seconds every time when, at a definite 
pressure, both curves are registered. Otherwise the respiration can 
always be more or less distinctly observed in the plethysmographic 
curve, which, though not rendering the reading impossible, causes 
at all events some difficulty. It is interesting, that even during a 
pressure in the compression-armlet far above the MB when certainly 
all the veins and arteries are tightly compressed, the respiration remains 
always distinctly visible in the curve. Even then every inspiration 
lowers the curve a little, every exspiration raises it, and this is the 
case just as well when compression-armlet and plethysmograph- 
band are both applied round the upper-arm, as when the former is 
applied round the upper-arm and the latter round the forearm, and 
consequently the influence of the one on the other is entirely exeluded. 
This influence of respiration is even to be observed, if the patient’s 
whole arm is tightly held by an assistant. We hope we shall he 
able to give an explanation of this phenomenon in a subsequent 
investigation. 
At present the communication suffices that in case we wish to obtain 
fine curves, the patient has to hold his breath each time. However, 
the moments, that interest us, can for the rest likewise be read with 
great accuracy with ordinary calm respiration. 
How strongly the plethysmograph-band and the compression armlet 
encircle the arm is of little consequence, if only one takes care to 
remain below the mp. This is of course easy to do, and is moreover 
quite usual. We did not observe a single exception in this respect, 
not even with very thick arms. And if in the beginning we remain 
below that pressure, the gradually more and more inflated compression- 
armlet will exceed the pressure of the plethysmograph-band ; conse- 
quently this is no longer of any account. There is, however, no 
objection to taking a wide band, which does not even press a thick 
