asure out 400 c.c. distilled water into a "tared" 2-litre flask.

2. Weigh out 15 grammes agar and mix into a thick paste with 100 c.c.
cold distilled water, and add to the flask.

3. Dissolve the agar by bubbling live steam through the mixture as in
making nutrient agar.

4. Weigh out 250 grammes haricot beans, place in the flask with the agar
mixture.

5. Add 1 c.c. of 1 per cent. aqueous solution sodium bicarbonate.

6. Weigh out 10 grammes sodium chloride and add to the contents of the
flask.

7. Place in the steamer at 100 deg. C. for thirty minutes.

8. Adjust the weight of the medium mass to 1030 grammes (the figure per
litre obtained experimentally) by the addition of distilled water at
100 deg. C.

9. Cool to 60 deg. C., clarify with egg and filter.

10. Weigh out 20 grammes saccharose and add to the contents of the
flask.

11. Tube, and sterilise as for nutrient agar.

~Wood Ash Agar.~--

1. Measure 400 c.c. distilled water into a tared 2-litre flask.

2. Weigh out 10 grammes agar and make into a thick paste with 100 c.c.
cold distilled water.

3. Add this agar paste to the distilled water in the flask.

4. Dissolve the agar by passing live steam through it, as in preparing
nutrient agar.

5. Weigh out 5 grammes clean wood ash and place in a second flask
containing 200 c.c. distilled water with some sterile glass beads: shake
thoroughly in a mechanical shaker for ten minutes.

6. Heat in steamer at 100 deg. C., for thirty minutes.

7. After removal from the steamer dry the outside of the flask
thoroughly, place it over a Bunsen flame and boil for one minute.

8. Filter directly into the flask containing the melted agar mixture.

9. Weigh out 4 grammes maltose. Add to the contents of the flask.

10. Adjust the weight of the medium mass to the calculated figure for
one litre (1019 grammes) by the addition of distilled water at 100
deg. C.

11. Replace the flask in the steamer for twenty minutes, cool to 60
deg. C., and clarify with egg and filter.

12. Tube, and sterilise as for nutrient agar.

_Media for the Study of Special Bacilli._

_B. Acnes._

~Oleic Acid Agar (Fleming).~--

1. Measure out into a sterile stout glass bottle which already contains
about 10 sterile glass beads

Ascitic fluid 250 c.c.

2. Weigh out

Oleic acid 25 grammes

and add it to the ascitic fluid in the bottle.

3. Emulsify evenly by shaking (either