After allowing it to
remain at rest long enough to permit subsidence of all that will settle,
the stopper is gently turned and a drop taken off the lower end upon a
slide, to be examined at leisure with the microscope. The cap, ground and
fitted upon the lower end, is put there as a precautionary measure, as
will be seen farther on.
[Illustration: VANDERPOEL'S SETTLING TUBES.]
The tube shown at 4 is, we think, an improvement upon all of the
foregoing, for upon it there is no side tube to break off, and everything
is comprised in a small space. As will be seen by referring to the
figure, there is a slight enlargement in the ground portion of the
stopper end of the tube, this protuberance coming down about one-half the
length of the stopper, which is solid and ground to fit perfectly. The
lower half, however, is provided with a small longitudinal slit or
groove, the lower end of which communicates with the interior of the
tube, while the upper end just reaches the enlargement in the side of the
latter. Thus in one position of the stopper there is a communication
between the tube and the outer air, while in all other positions the tube
is quite shut. In all these tubes care must be taken to fill them
_completely_ with the urine, and to allow no bubbles of air to remain
therein.
The first of these settling tubes was made without the ground cap on the
lower end, the latter being inserted into a small test tube for safety.
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