tube No. 1a and agar tube No. 1. Flame the plugs and
remove them from the tubes (retaining the plug of the agar tube in the
hand); flame the mouths of the tubes, pour the serum into the tube of
liquefied agar and replace the plug of the agar tube.

3. Mix thoroughly and pour plate No. 1 _secundum artem_.

4. Treat the remaining tube of agar and serum in a similar fashion, and
pour plates Nos. 2 and 3.

5. Dry the serum agar plates in the incubator running at 60 deg. C. for
one hour (see page 232).

6. Inoculate the plates in series as described for gelatine surface
plates (page 231).

(e) _Blood Agar, Human._--

1. Melt a tube of sterile agar and pour it into a sterile plate; let it
set.

2. Collect a few drops of human blood, under all aseptic conditions, in
a sterile capillary teat pipette.

3. Raise the cover of the Petri dish very slightly, insert the extremity
of the capillary pipette, and deposit the blood on the centre of the
agar surface. Close the dish.

4. Charge a platinum loop with a small quantity of the inoculum. Raise
the cover of the plate, introduce the loop, mix its contents with the
drop of blood, remove the loop, close the dish and sterilise the loop.

5. Finally smear the mixture over the surface of the agar with a
sterilised L-shaped rod.

6. Label and incubate.

(If considered necessary, two, three, or more similar plates may be
inoculated in series.)

(f) _Blood Agar, Animal._--

When preparing citrated blood agar (page 171) it is always advisable to
pour several blood agar tubes into plates, which can be stored in the
ice chest ready for use at any moment for surface plate cultures.

(g) Hanging-drop or block culture, (_vide_ page 233).

~3. Serial Cultivations.~--These are usually made upon agar or
blood-serum, although gelatine may also be used.

The method is as follows:

1. Take at least four "slanted" tubes of media and number them
consecutively.

2. Flame all the plugs and see that each can be readily removed.

3. Charge the platinum loop with a small quantity of the inoculum,
observing the usual routine, and plant tube No. 1, smearing thoroughly
all over the surface. If any water of condensation has collected at the
bottom of the tube, use this as a diluent before smearing the contents
of the loop over the surface of the medium.

4. Without sterilising or recharging the loop, inoculate tube No. 2, by
making three parallel streaks from end to end of the slanted