rough Swedish filter paper.

6. Tube in quantities of 10 c.c. or store in flasks.

7. Sterilise in the steamer at 100 deg. C. for twenty minutes on each of
three consecutive days.

The natural reaction of the wort should _not_ be interfered with.

NOTE.--It is sometimes more convenient to obtain
"_unhopped_"[6] beer wort direct from the brewery. In this
case it is diluted with an equal quantity of distilled
water, steamed for an hour, filtered, filled into sterile
flasks or tubes, and sterilised by the discontinuous method.

~Wort Gelatine.~--

1. Measure out wort (prepared as above), 900 c.c., into a sterile flask.

2. Weigh out gelatine, 100 grammes (= 10 per cent.), and add it to the
wort in the flask.

3. Bubble live steam through the mixture for ten minutes, to dissolve
the gelatine.

4. Cool to 60 deg. C.; clarify with egg as for nutrient gelatine
(_vide_ page 164).

5. Filter through papier Chardin.

6. Tube, and sterilise as for nutrient gelatine.

~Wort Agar.~--

1. Measure out wort (as above), 700 c.c., into a sterile flask.

2. Weigh out powdered agar, 20 grammes; mix into a smooth paste with 200
c.c. of cold wort and add to the wort in the flask.

3. Bubble live steam through the mixture for twenty minutes, to dissolve
the agar.

4. Cool to 60 deg. C.; clarify with egg as for nutrient agar (_vide_ page
167).

5. Filter through papier Chardin, using the hot-water funnel.

6. Tube, and sterilise as for nutrient agar.

~Peptone Water (Dunham).~--

1. Weigh out Witte's peptone, 10 grammes, and salt, 5 grammes, and
emulsify with about 250 c.c. of distilled water previously heated to
60 deg. C.

2. Pour the emulsion into a litre flask and make up to 1000 c.c. by the
addition of distilled water.

3. Heat in the steamer at 100 deg. C. for thirty minutes.

4. Filter through Swedish filter paper.

5. Tube in quantities of 10 c.c. each.

6. Sterilise in the steamer at 100 deg. C. for twenty minutes on each of
three consecutive days.

~"Sugar" or "Carbohydrate" Media.~--

Formerly the ability of bacteria to induce hydrolytic changes in
carbohydrate substances was observed only in connection with a few
well-defined sugars, but of recent years it has been shown that when
using litmus as an indicator these so-called "fermentation reactions"
facilitate the differentiation of closely allied species, and the list
of substances employed in this connection has