Meat Extract on a
piece of clean filter paper and add to the water in the
flask. Shake the flask well to make an even emulsion of the
meat extract.

3. Weigh out Witte's peptone (10 grammes), salt (5 grammes).
Mix into smooth paste with 100 c.c. distilled water
previously heated to 60 deg. C.

4. Add the peptone salt emulsion to the meat extract
emulsion in the flask and add 650 c.c. distilled water. Heat
in the steamer for forty-five minutes.

5. Standardise the medium and complete as for nutrient
bouillon.

~Nutrient Gelatine.~--

1. Weigh a 2-litre flask on a trip balance (Fig. 106) and note the
weight, or counterpoise carefully.

[Illustration: FIG. 106.--Trip balance.]

An extremely useful counterpoise is a small sheet-brass cylinder about
38 mm. high and 38 mm. in diameter, with a funnel-shaped top and
provided with a side tube by which its contents, fine "dust" shot, may
be emptied out (Fig. 107).

[Illustration: FIG. 107.--Counterpoise; weight when empty, 35 grammes;
when full of dust shot, 200 grammes.]

2. Measure out double strength meat extract, 500 c.c., into the "tared"
flask.

3. Weigh out and mix 10 grammes of peptone, 5 grammes of salt, and make
into a thick paste with 150 c.c. distilled water; then add the emulsion
to the meat extract in the flask; also add 100 grammes sheet gelatine
cut into small pieces; place the flask in the water-bath and raise to
the boil.

[Illustration: FIG. 108.--Arrangement of steam can and water-bath for
the preparation of media.]

4. Arrange a 5-litre tin can (with copper bottom, such as is used in the
preparation of distilled water) by the side of the water bath, fill the
can with boiling water and place a lighted Bunsen burner under it. Fit a
long safety tube to the neck of the can and also a delivery tube, bent
twice at right angles; adjust the tube to reach to the bottom of the
interior of the flask containing the gelatine, etc. (Fig. 108).

5. Keep the water in the steam can vigourously boiling, and so steam at
100 deg. C, bubbling through the medium mass, for ten minutes, by
which time complete solution of the gelatine is effected. A certain
amount of steam will condense as water in the medium flask during this
process--hence the necessity for the use of double strength meat
extract--but if the water bath is kept boiling this condensation will
not exceed 100 c.c.

6. Weigh the flask and its co