lustration: FIG. 21.--Fermentation tubes.]

~Fermentation Tubes~ (Fig. 21).--These are used for the collection and
analysis of the gases liberated from the media during the growth of some
varieties of bacteria and may be either plain (a) or graduated (b).
A simple form (Fig. 21, c) may be made from 14 cm. lengths of soft
glass tubing of 1.5 cm. diameter. The Bunsen flame is applied to a spot
some 5 cm. from one end of such a piece of tubing and the tube slightly
drawn out to form a constriction, the constricted part is bent in the
bat's-wing flame, to an acute angle, and the open extremity of the long
arm sealed off in the blowpipe flame. The open end of the short arm is
rounded off and then plugged with cotton-wool, and the tube is ready for
sterilisation.

CLEANING OF GLASS APPARATUS.

All glassware used in the bacteriological laboratory must be thoroughly
cleaned before use, and this rule applies as forcibly to new as to old
apparatus, although the methods employed may vary slightly.

~To Clean New Test-tubes.~--

1. Place the tubes in a bucket or other convenient receptacle, fill with
water and add a handful of "Sapon" or other soap powder. See that the
tubes are full and submerged.

2. Fix the bucket over a large Bunsen flame and boil for thirty
minutes--or boil in the autoclave for a similar period.

3. Cleanse the interior of the tubes with the aid of test-tube brushes,
and rinse thoroughly in cold water.

4. Invert the tubes and allow them to drain completely.

5. Dry the tubes and polish the glass inside and out with a soft cloth,
such as selvyt.

~New flasks, plates, and capsules~ must be cleaned in a similar manner.

~To Clean New Graduated Pipettes.~--

1. Place the pipettes in a convenient receptacle, filled with water to
which soap powder has been added.

2. Boil the water vigorously for twenty minutes over a Bunsen flame.

3. Rinse the pipettes in running water and drain.

4. Run distilled water through the pipettes and drain.

5. Run rectified spirits through the pipette and drain as completely as
possible.

6. Place the pipettes in the hot-air oven (_vide_ page 31), close the
door, open the ventilating slide, and run the temperature slowly up to
about 80 deg. C. Turn off the gas and allow the oven to cool.

Or 6a. Attach each pipette in turn to the rubber tube of the foot
bellows, or blowpipe air-blast, and blow air through the pipette until
the interior is dry.

Glassware that