ted figure for one
litre (1040 grammes).

7. Cool to 60 deg. C. and clarify with egg as for nutrient agar (_vide_
page 168).

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

9. Weigh out lactose, 10 grammes (= 1 per cent.), and dissolve it in the
agar.

If desired, add 5 c.c. of a 1 per cent. (= 0.5 per cent.) aqueous
solution of neutral red.

10. Tube, and sterilise as for nutrient agar.

~Litmus Nutrose Agar (Drigalski-Conradi).~--

This medium should be prepared in precisely the same manner as the
Nutrose agar described on page 172 substituting meat extract for serum
water, and increasing the percentage of agar added per litre to 3 per
cent.

~Fuchsin Agar (Braun).~--

1. Liquefy and measure out into a sterile flask:

Nutrient agar 1000 c.c.

2. Weigh out: lactose 10 grammes and dissolve in the fluid agar.

3. Adjust the reaction to -5 and filter.

4. Measure out and mix thoroughly with agar:

Fuchsin, alcoholic solution 5 c.c.

The fuchsin solution is prepared by mixing:

Fuchsin (basic) 3 grammes.
Absolute alcohol 60 c.c.

Allow to stand twenty-four hours, then centrifugalise thoroughly and
decant the supernatant fluid into a well-stoppered bottle.

5. Measure out and add to the nutrient agar, sodium sulphite, 10 per
cent. aqueous solution, freshly prepared 25 c.c.

6. Tube and sterilise as for nutrient agar.

7. Store in a dark cupboard.

~Fuchsin Sulphite Agar (Endo).~--

1. Liquefy and measure out into a sterile flask:

Nutrient agar 1000 c.c.

2. Weigh out

Lactose 10 grammes.

and dissolve in the fluid agar.

3. Adjust the reaction to +3 and filter.

4. Measure out and mix thoroughly with the fluid agar.

Fuchsin, alcoholic solution (_vide supra_) 5 c.c.

5. Measure out and add to the medium

Sodium sulphite, 10 per cent. aqueous solution 25 c.c.

6. Tube and sterilise as for nutrient agar.

~Brilliant Green Agar (Conradi).~--

1. Liquefy and measure out into a sterile flask

Nutrient agar 1000 c.c.

2. Adjust reaction to +30 by the addition of normal phosphoric acid; and
filter.

3. Measure out and mix thoroughly with the fluid medium

Brilliant green (Hoechst) 1 per thousand aqueous solution 6.5 c.c.

4. Measure out and add to the medium

Picric acid (Gruebler), 1 per cent. aqueous solution 6.5 c.c.

5. Tube and sterilise