ee that it fits the mouth of the tube accurately.

3. Remove the stopper from the caustic soda bottle.

4. Drop one of the pyrogallic acid tablets[9] into the Buchner's tube
(roughly, use 1 gramme pyrogallic acid for every 100 c.c. air capacity
of the receiving vessel).

5. Add about 1 c.c. of the soda solution.

6. Place the inoculated tube inside the Buchner's tube. The pyrogallic
tablet acts as a buffer and prevents damage to either the inoculated
tube or the Buchner's tube even should it be slipped in hurriedly.

7. Fit the india-rubber stopper tightly into the mouth of the Buchner's
tube.

[Illustration: FIG. 130.--Buchner's tube.]

The pyrogallic acid tablet dissolves slowly in the soda solution and its
oxidation proceeds very slowly at first so that ample time is available
when this method is adopted.

8. Restopper the caustic soda bottle.

9. Place Buchner's tube in a wire support, and incubate.

~Method VII~ (Wright's Method).--

1. Prepare tube cultivation in the usual way.

2. Cut off that portion of the cotton-wool plug projecting above the
mouth of the tube with scissors, then push the plug into the tube for a
distance of 2 or 3 cm.

3. By means of a pipette drop about 1 c.c. of pyrogallic acid 10 per
cent. aqueous solution on to the plug. It will immediately be absorbed
by the cotton-wool.

4. With another pipette run in an equal quantity of the caustic soda
solution.

5. Quickly close the mouth of the tube with a tightly fitting
india-rubber stopper.

6. Incubate.

[Illustration: FIG. 131.--McLeod's anaerobic plate base with half petri
dish inverted _in situ_]

~Method VIII~ (McLeod's Method).--

~Apparatus and Solutions Required.~--

McLeod's plate base (a hollow glazed earthenware disc 9 cm.
in diameter and 2 cm. deep: the upper surface is pierced by
a central hole, 2 cm. in diameter, giving access to the
interior, the lower part of which is divided into two by a
low partition. A shallow groove encircles the upper surface
near to the edge).

Plasticine.
Pyrogallic acid (1 gramme) compressed tablets.
Sodic hydroxide (0.4 gramme) compressed tablets.
Wash bottle of distilled water.
Surface plates of one or other agar medium (in petri dishes
of 8 cm. diameter).
Surface plate spreader.

METHOD.--

1. Roll out a long cylinder of plasticine and fit it into the groove on
the upper surface of the earthenware base.