ogen gas supply by
means of rubber tubing.

[Illustration: FIG. 135.--Novy's jar for plate cultivations.]

[Illustration: FIG. 136.--Novy's jar for tube cultivations.]

5. Attach a piece of rubber tubing to the exit tube b and collect
samples of the issuing gas (over water) and test from time to time.

6. When the air is completely displaced by hydrogen, turn the handle of
the stopper at right angles to the line of entry and exit tubes; this
seals the orifice of both tubes.

7. Disconnect the gas apparatus and incubate.

(E) ~Method XII~ (Bulloch's Method).--

~Apparatus Required.~--

Bulloch's jar.
Pot of resin ointment.
Small glass dish 14 cm. diameter by 5 cm. deep.
Vessel for tube cultures or metal rack for plate cultures.
Pyrogallic acid tablets.
Cylinder of compressed hydrogen.
Geryk or other air pump.
Rubber pressure tubing.
10 c.c. pipette.
Glass tubing.
Dry granulated caustic soda or compressed tablets each, containing
0.4 grammes sodic hydroxide.
Small beaker of water.

METHOD.--

1. Prepare the cultivations in the usual way.

2. Place the glass dish in the centre of the glass slab, and stand the
cultivations inside this.

3. Place a sufficient number of pyrogallic acid tablets at one side of
the glass dish (i. e., 1 tablet for each 100 cubic centimeters air
capacity of the bell jar). Place a small heap of dry granulated soda (or
half a dozen tablets of sodic hydroxide) by the side of the pyro
tablets.

4. Smear the flange of the bell jar with resin ointment and apply the
jar firmly to the glass slab, covering the cultivations--so arranged
that the long tube passes with its lower end into the glass dish at a
point directly opposite to the pyrogallic acid tablets. Lubricate the
two stop-cocks with resin ointment (Fig. 137).

5. Connect up the short tube a with the gas-supply by means of rubber
pressure tubing and open both stop-cocks.

6. Connect a long, straight piece of glass tubing to the long tube b
by means of a piece of rubber tubing interposing a screw clamp: and
collect samples of the issuing gas from time to time and test.

7. When the air is displaced, shut off the stop-cock of the entry tube,
then that of the exit tube b. Screw down the clamp and remove the
glass tube from the rubber connection and connect up the short tube a
to the air pump by means of pressure tubing.

8. Open the stop-cock of tube a and with two or