on (Pakes).~--

1. Weigh out Witte's peptone, 10 grammes, and emulsify it with 200 c.c.
ammonia-free distilled water previously heated to 60 deg. C.

2. Wash the emulsion into a flask and make up to 1000 c.c., with
ammonia-free distilled water.

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

4. Weigh out sodium nitrate, 1 gramme, and dissolve in the contents of
the flask.

5. Filter through Swedish filter paper.

6. Tube, and sterilise as for nutrient bouillon.

~Litmus Bouillon.~--

1. Measure out nutrient bouillon, 1000 c.c. (_vide_ page 163, sections 1
to 6).

2. Add sufficient sterile litmus solution to tint the medium a dark
lavender colour. (Media rendered +10 will usually react very faintly
alkaline or occasionally neutral to litmus.)

3. Tube, and sterilise as for bouillon.

~Rosolic Acid Peptone Solution.~--

1. Weigh out rosolic acid (corallin), 0.5 gramme, and dissolve it in 80
per cent. alcohol, 100 c.c. Keep this as a stock solution.

2. Measure out peptone water (Dunham), 100 c.c., and rosolic acid
solution, 2 c.c., and mix.

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

4. Filter through Swedish filter paper.

5. Tube, and sterilise as for nutrient bouillon.

~Capaldi-Proskauer Medium, No. I.~--

1. Weigh out and mix

Sodium chloride 2.0 grammes
Magnesium sulphate 0.1 gramme
Calcium chloride 0.2 gramme
Monopotassium phosphate 2.0 grammes

2. Dissolve in water 1000 c.c. in a 2-litre flask

3. Weigh out and mix

Asparagin 2 grammes
Mannite 2 grammes

and add to contents of flask.

4. Measure out 25 c.c. of the solution and titrate it against decinormal
sodic hydrate, using litmus as the indicator. Control the result and
estimate the amount of sodic hydrate necessary to be added to render the
remainder of the solution neutral to litmus. Add this quantity of sodic
hydrate.

5. Filter.

6. Add litmus solution 47.5 c.c. (= 5 per cent.).

7. Tube, and sterilise as for nutrient bouillon.

~Capaldi-Proskauer Medium No. II.~--

1. Weigh out and mix

Peptone 20 grammes
Mannite 1 gramme

2. Dissolve in water 1000 c.c. in a 2-litre flask.

3. Neutralise to litmus as in No. I (_vide supra_, Step 4).

4. Filter.

5. Add litmus solution 47.5 c.c. (= 5 per cent.).

6. Tube, and sterilise as for nutrient bouillon.

~Urine Media. Bouillon.~--

1. Collect freshl