k for the neck of Winchester quart, perforated
with two holes and fitted with one 6 cm. length of straight
glass tubing, and one V-shaped piece of glass tubing, one
arm 32 cm. in length, the other 52 cm., the shorter arm
being plugged with cotton-wool. The rubber stopper must be
sterilised by boiling and the glass tubing by hot air,
before use.

Flask containing 250 c.c. sterile broth.

Test-tube brush to fit the lumen of the candle, enclosed in
a sterile test-tube (and previously sterilised by dry heat
or by boiling).

Case of sterile pipettes, 10 c.c. in tenths.

Case of sterile pipettes, 1 c.c. in tenths.

Case of sterile pipettes, 1 c.c. in hundredths.

Tubes of various nutrient media (according to requirements).

Twelve Buchner's tubes with rubber stoppers.

Pyrogallic acid tablets.

Caustic soda tablets.

[Illustration: Sample form]]

[Illustration: FIG. 209.--Water filtering apparatus. That portion of the
figure to the left of the vertical line is drawn to a larger scale than
that on the right, in order to show details of Sprengel's pump.]

METHOD.--

1. Fit up the filtering apparatus as in the accompanying diagram (Fig.
209), interposing the wash-bottle with sulphuric acid between the
filter flask and the force-pump (in the position occupied in the diagram
by the central vertical line), and placing another screw clamp on the
rubber tubing connecting the lateral arm of the filter flask with the
wash-bottle.

[Illustration: FIG. 210. Sterile test-tube brush.]

2. Filter the entire 2000 c.c. of water through the filter candle.

3. When the nitration is completed, screw up the clamps and so occlude
the two pieces of pressure tubing.

4. Reverse the position of the glass tubes in the Wulff's bottle so that
the one nearest the air pump now dips into the sulphuric acid.

5. Slowly open the metal clamps and allow air to gradually pass through
the acid, and enter filter flask, and so restore the pressure.

6. Unship the apparatus, remove the cork from the mouth of the candle.

7. Pipette 10 c.c. of sterile broth into the interior of the candle, and
by means of the sterile test-tube brush (Fig. 210) emulsify the slimy
residue which lines the candle, with the broth.

Practically all the bacteria contained in the original 2000 c.c. of
water are now suspended in 10 c.c. of broth, so that 1 c.c. of the
suspension is