2. Place a tablet of pyrogallic acid in one division of the interior of
the plate base, and two tablets of sodic hydroxide in the other.

3. Prepare surface plate culture of the organism to be cultivated.

4. Run a few cubic centimetres of distilled water into that division of
the plate base containing the sodic hydroxide.

5. Invert the bottom half of the surface plate over the plate base and
press its edges firmly down into the plasticine filling the groove.

6. Label and incubate.

(D) ~Method IX.~--

~Apparatus Required.~--

Small Ruffer's or Woodhead's flask (Fig. 33).
Sterile india-rubber stopper.
India-rubber tubing.
Glass tubing.
Metal screw clips.
Cylinder of compressed hydrogen; or hydrogen gas apparatus

METHOD.--

1. Sterilise a glass vessel, shaped as in a Ruffer's or Woodhead's
flask, in the hot-air oven. (The tubulure and the side tubes are plugged
with cotton-wool.) After sterilisation, fix a short piece of rubber
tubing occluded by a metal clip to each side tube.

2. Inoculate a large quantity (e. g., 200 c.c.) of the medium. Where
solid media are employed they must first be liquefied by heat.

3. Remove the cotton-wool plug from the tubulure and pour the inoculated
medium into the glass vessel.

4. Close the tubulure by means of an india-rubber stopper previously
sterilised by boiling in a beaker of water.

[Illustration: FIG. 132.--Kipp's hydrogen apparatus, (a) connected up
to two washing bottles containing (b) lead acetate 10 per cent.
solution, to remove H_{2}S and (c) silver nitrate solution to remove
AsH_{3}. A third washing bottle containing pyrogallic acid 10 per cent.
solution, rendered alkaline, to remove any trace of oxygen, is sometimes
introduced.]

[Illustration: FIG. 133.--Improved gas apparatus; the metal is contained
in a perforated glass tube which is submerged in acid when the
triangular bottle is upright (a), but is above the level of the liquid
when the bottle is turned on its side (b).]

5. Connect up the india-rubber tubing on one of the side tubes with a
cylinder of compressed hydrogen (or the delivery tube of a Kipp's Fig.
132 or other hydrogen apparatus, Fig. 133), interposing a short piece of
glass tubing; and in like manner connect a long piece of rubber tubing
which should be led into a basin of water, to the opposite side tube.

6. Open both metal clips and pass hydrogen through the vessel until the
atmospheric air is repl