ted from the rabbit's
heart to a small Erlenmeyer flask containing a number of sterile glass
beads and 5 c.c. concentrated sod. citrate solution. (See page 378.)

10. Agitate thoroughly and set aside for a couple of hours.

11. Melt up several tubes of nutrient agar (see page 167) and cool to
42 deg. C.

12. With a sterile 10 c.c. graduated pipette transfer 1 c.c. citrated
blood from the Erlenmeyer flask to each tube of liquefied agar. Rotate
the tube between the hands in order to diffuse the citrated blood evenly
throughout the agar.

13. Place the tubes in a sloping position and allow the medium to set.

14. Place tubes of blood agar for forty-eight hours in the incubator at
37 deg. C. and at the end of that time eliminate any contaminated tubes.

15. Store such tubes as remain sterile for future use.

~Milk.~--

1. Pour 1 litre of fresh cow's or goat's milk into a large separating
funnel, and heat in the steamer at 100 deg. C. for one hour.

2. Remove from the steamer and estimate the reaction of the milk (normal
cows' milk averages +17). If of higher acidity than +20, or lower than
+10, reject this sample of milk and proceed with another supply of milk
from a different source.

Reject milk to which antiseptics have been added as preservatives.

3. Allow the milk to cool, when the fat or cream will rise to the
surface and form a thick layer.

4. Draw off the subnatant fat-free milk into sterile tubes (10 c.c. in
each).

5. Sterilise in the steamer at 100 deg. C. for twenty minutes on each of
five successive days.

6. Incubate at 37 deg. C. for forty-eight hours and eliminate any
contaminated tubes. Store the remainder for future use.

~Litmus Milk.~--

1. Prepare milk as described above, sections 1 to 3.

2. Draw off the subnatant fat-free milk into a flask.

3. Add sterile litmus solution, sufficient to colour the milk a deep
lavender.

4. Tube, sterilise, etc., as for milk.

~Nutrose Agar (Eyre).~--

(This is a modification of the well known Drigalski-Conradi medium
originally introduced for the isolation of B. typhosus).

1. Collect 250 c.c. perfectly fresh ox serum (_vide_ Blood Serum, page
168, steps 1 to 5) and add to it 450 c.c. sterile distilled water.

2. Weigh out agar powder, 20 grammes, and emulsify it with 250 c.c. of
the cold serum water.

3. Weigh out

Witte's peptone 10 grammes
Sodium chloride 5 grammes
Nutrose 10 gramme