frequently a good deal of doubt, even after large experience, as to
just the moment at which the fourth phase begins. With the
understanding that the difference is only a few millimeters, which
is of very little importance, when the diastolic pressure is below
95, it seems advisable to urge the reading of the diastolic pressure
at the beginning of the fifth phase.

The incident of the first phase, or when sound begins, is caused by
the sudden distention of the blood vessel below the point of
compression by the armlet. In other words, the armlet pressure has
at this point been overcome. Young [Footnote: Young: Indiana State
Med. Assn. Jour., March, 1914.] believes that the murmurs of the
second phase, which in all normal conditions are heard during the 20
mm. drop below the point at which the systolic pressure had been
read, is "due to whirlpool eddies produced at the point of
constriction of the blood vessel by the cuff of the instrument." The
third phase is when these murmurs cease and the sound resembles the
first, lasting he thinks for only 5 mm. The third phase often lasts
much longer. He thinks the fourth phase, when the sound becomes
dull, lasts for about 6 mm.


TECHNIC

It is essential that the patient on whom the examination is to be
made should be at rest, either comfortably seated, or lying down.
All clothing should be removed from the arm, and there should be no
constriction by sleeves, either of the upper arm or the axilla. When
the blood pressure is taken over the sleeve of a garment, the
instrument will register from 10 to 30 mm. higher than on the bare