packing, in the vertical position, in oblong boxes having an internal
measurement of 37 cm. long by 12 cm. wide by 10 cm. deep. Each box (Fig.
105) has a movable partition formed by the vertical face of a weighted
triangular block of wood, sliding free on the bottom (Fig. 105, A); or
by a flat piece of wood sliding in a metal groove in the bottom of the
box, which can be fixed at any spot by tightening the thumbscrew of a
brass guide rod which transfixes the partition (Fig. 105, B). The front
of the box is provided with a handle and a celluloid label for the name
of the contained medium. These boxes are arranged upon shelves in a dark
cupboard--or preferably an iron safe--which should be rendered as nearly
air-tight as possible, and should have the words "media stores" painted
on its doors.

[Illustration: FIG. 105.--Medium box, showing alternative partitions A
and B.]

FOOTNOTES:

[3] This rubber cap has been made for me by the Holborn Surgical
Instrument Co., Thavies Inn, London, W. C.

XI. CULTURE MEDIA.

ORDINARY OR STOCK MEDIA.

~Nutrient Bouillon.~--

1. Measure out double strength meat extract, 500 c.c., into a litre
flask and add 300 c.c. distilled water.

2. Weigh out Witte's peptone, 10 grammes (= 1 per cent.), salt, 5
grammes (= 0.5 per cent.), and mix into a smooth paste with 200 c.c. of
distilled water previously heated to 60 deg. C. (Be careful to leave no
unbroken globular masses of peptone.)

3. Add the peptone emulsion to the meat extract in the flask and heat in
the steamer for forty-five minutes (to completely dissolve the peptone,
and to render the acidity of the meat extract stable).

4. Estimate the reaction of the medium; control the result; render the
reaction of the finished medium +10 (_vide_ page 155).

5. Heat for half an hour in the steamer at 100 deg. C. (to complete the
precipitation of the phosphates, etc.).

6. Filter through Swedish filter paper into a sterile flask.

7. Fill into sterile tubes (10 c.c. in each tube).

8. Sterilise in the steamer for twenty minutes on each of three
consecutive days--i. e., by the discontinuous method (_vide_ page 35).

NOTE.--As an alternative method when neither fresh nor
frozen meat is available nutrient bouillon may be prepared
from a commercial meat extract, as follows:

~Lemco Broth.~--

1. Measure out 250 c.c. distilled water into a litre flask.

2. Weigh out 10 grammes Liebig's Lemco