x" 1 - c - 4 Shaw: Microtechnical Methods 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. 



