252 The Philippine Journal of Science ms 
means of regulating the maximum pressure of the water under 
the filter floor. The assembled apparatus in use is represented 
by fig. 3. 
In use the bend of the U tube is first filled with distilled water 
to a level somewhat above the filter floor. Then, with the inlet 
mouth and side tube closed, the tube is inverted with the filter 
side lowermost, and shaken if necessary, to release all air bub- 
bles from below the filter. It is returned to the upright posi- 
tion and hung on a suitable sup- 
port. Next, the open side is 
filled with water up to the level 
of the outlet, and the liquid con- 
taining the specimens is quickly 
poured into the other side, the 
object being to prevent any fix- 
ing fluid from passing through 
the filter. In practice it is pref- 
erable to decant superfluous fix- 
ing fluid and dilute before pour- 
ing into the washing apparatus. 
After the specimens have been 
allowed to settle, a narrow wick 
of several layers of filter paper, 
pointed at the outer end, is in- 
serted in the outlet tube to in- 
sure a steady outflow. The bent 
tube on the side tube of the inlet 
arm is provided v/ith a similar 
wick and adjusted to provide 
for the maximum limit of pres- 
sure. Washing water is allowed 
to drop into the inlet mouth of 
the U tube. 
A form of this apparatus having a larger capacity is made 
by using an Erlenmeyer flask from which the bottom has been 
cut with a diamond, the edges smoothed by heating over a flame, 
and a spout, like that of a beaker, shaped in the larger end 
as shown in fig. 4. The flasks used have a nearly cylindrical 
neck about 4 cm long and 33 mm inside diameter, and it is 
preferable that this inside diameter be smallest near the union 
of the neck with the conical body of the flask. A ring dia- 
phragm to fit tightly in the neck is cut from a cork or rubber 
stopper. The aperture in the diaphragm should be large enough 
to permit the exit of bubbles which may form between the dia- 
Fig. 4. Larger washing apparatus made 
from a flask. Diaphragm of cork or rubber, 
d; filter paper, f; material, to; plug, p; 
supporting rod, n; rubber stopper with two 
holes, s; glass tubes, t and t' ; rubber con- 
nection, c; base, b; filter paper wicks, w 
and w' ; supply of water, x; wick in front 
view of lip, w." X J. 
