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253 
phragm and the filter floor. The rubber diaphragms are about 
10 mm thick and those of cork about 9. The mouth of the 
flask is provided with a two-hole rubber stopper, which fits 
tightly when about half of the stopper is within the neck. A 
channel is cut on the larger end from one hole to the margin. 
A glass tube of a size to fit snugly in the stopper hole is bent 
at right angles in two places so that one arm shall reach through 
the stopper from the channel to the smaller end of the stopper, 
and the other end shall extend upward in a vertical direction 
beyond the margin of the flask and a little higher than the 
filter floor. A straight piece of glass tubing, large enough to 
slip over the bent tube and long enough to reach from the bend 
of the small tube to the level of the flask spout, is provided on 
one end with a short piece of soft rubber tubing. If necessary, 
about 7 mm of this rubber tubing is turned back over itself 
to make it fit snugly over the bent tube. The inner end of 
the other hole in the stopper is plugged with a piece of tightly 
fitting glass rod or with beeswax-resin cement. A piece of 
wood to serve as a base for the apparatus is fitted with an 
upward projecting metal rod of a size to fit snugly in the 
stopper perforation and to reach almost up to the plug. The 
arrangement and use of this apparatus are shown in fig. 4. 
To prepare the apparatus for use a piece of filter paper is 
placed over the mouth of the flask and pressed into the neck 
with the diaphragm, which is introduced larger side first. 
When the smaller side is flush with the mouth the paper is 
trimmed, and then the diaphragm is pressed, with a loosely fit- 
ting cork, so far into the neck as to be well beyond the reach 
of the stopper. Holding the flask mouth upward under a flow- 
ing stream of water, the neck is filled from filter floor to brim 
with care to exclude bubbles, the stopper is inserted with 
its bent tube in place, and the apparatus immediately inverted 
and placed in position on its base. Water is added to the level 
of the free arm of the bent tube. The larger tube with its 
rubber connection is slipped over the bent tube and filled with 
water, and immediately the specimens in fixing fluid, preferably 
previously diluted, are poured into the space above the filter 
floor. The specimens are allowed to settle, a filter paper wick 
is placed in the spout to insure steady outflow, and inflow of 
water into the tube is provided. The height of the inflow tube 
is adjusted to fix the maximum limit of pressure and rate of 
flow. Washing can be hastened by occasionally siphoning off 
the liquid from above the specimens, provided the filter paper 
will withstand the increased pressure. 
