ve in the
hot gelatine.

3. Filter through papier Chardin.

4. Tube, and sterilise as for nutrient gelatine.

~Sugar Agar.~--

1. Prepare nutrient agar (_vide_ page 167, sections 1 to 8). Measure out
1000 c.c.

2. Weigh out glucose, 20 grammes (= 2 per cent.), and dissolve in the
clear agar.

3. Tube, and sterilise as for nutrient agar.

NOTE.--Other "sugar" media are prepared by substituting a
corresponding percentage of lactose, maltose (or any other
of the substances referred to under "Sugar Media," page 177)
for the glucose.

~Iron Bouillon.~--

1. Measure out nutrient bouillon, 1000 c.c. (_vide_ page 141, sections 1
to 6).

2. Weigh out ferric tartrate, 1 gramme (= 0.1 per cent.), and dissolve
it in the bouillon.

3. Tube, and sterilise as for bouillon.

NOTE.--The lactate of iron may be substituted for the
tartrate.

~Lead Bouillon.~--

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

2. Weigh out lead acetate, 1 gramme (= 0.1 per cent.), and dissolve it
in the bouillon.

3. Tube, and sterilise as for bouillon.

~Nitrate Bouillon.~--

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

2. Weigh out potassium nitrate, 5 grammes (= 0.5 per cent.), and
dissolve it in the bouillon.

3. Tube, and sterilise as for bouillon.

NOTE.--The nitrate of sodium or ammonium may be substituted
for that of potassium, or the salt may be added in the
proportion of from 0.1 to 1 per cent. to meet special
requirements.

~Iron Peptone Solution (Pakes).~--

1. Weigh out peptone, 30 grammes, and emulsify it with 200 c.c. tap
water, previously heated to about 60 deg. C.

2. Wash the emulsion into a litre flask with 800 c.c. tap water.

3. Weigh out salt, 5 grammes, and sodium phosphate, 3 grammes, and
dissolve in the mixture in the flask.

4. Heat the mixture in the steamer at 100 deg. C. for thirty minutes,
to complete the solution of the peptone, and filter into a clean flask.

5. Fill into tubes in quantities of 10 c.c. each.

6. Add to each tube 0.1 c.c. of a 2 per cent. neutral solution of ferric
tartrate. (A yellowish-white precipitate forms.)

7. Sterilise as for nutrient bouillon.

~Lead Peptone Solution.~--

Prepare as for iron peptone solution but in step 6 substitute 0.1 c.c.
of a 1 per cent. neutral aqueous solution of lead acetate.

~Nitrate Peptone Soluti