up to one litre exactly.

_Diplococcus Pneumoniae._

~Blood Agar (Washbourn).~--

1. Melt up several tubes of nutrient agar (_vide_ page 167) and allow
them to solidify in the oblique position.

2. Place the tubes, in the horizontal position, in the "hot" incubator
for forty-eight hours, to evaporate off some of the condensation water.

3. Kill a small rabbit with chloroform and nail it out on a board (as
for a necropsy). Moisten the hair thoroughly with 2 per cent. solution
of lysol.

4. Sterilise several pairs of forceps, scissors, etc., by boiling.

5. Reflect the skin over the thorax with sterile instruments.

6. Open the thoracic cavity by the aid of a fresh set of sterile
instruments.

7. Open the pericardium with another set of sterile instruments.

8. Sear the surface of the left ventricle with a red-hot iron and remove
fluid blood from the heart by means of sterile pipettes (e. g., those
shown in Fig. 13, c).

9. Deliver a small quantity of the blood on the slanted surface of the
agar in each of the tubes, and allow it to run over the entire surface
of the medium.

10. Place the tubes in the slanting position and allow the blood to
coagulate.

11. Return the "blood agar" to the hot incubator for forty-eight hours
and eliminate any contaminated tubes. Store the remainder for future
use.

_Media for the Study of Mouth Bacteria Generally._

~Potato Gelatine (Goadby).~--

1. Prepare glycerine potato broth (see page 203, sections 1 to 5).

2. Add 10 per cent. gelatine to the potato decoction and bubble live
steam through the mixture for ten minutes.

3. Estimate the reaction; adjust the reaction of the medium to +5.

4. Cool the medium to below 60 deg. C., clarify with egg as for nutrient
gelatine.

5. Filter through papier Chardin.

6. Tube, and sterilise as for nutrient gelatine.

_Media for the Study of Protozoa._

~Tissue Medium (Noguchi).~--_For spirochaetes (cultivations must be grown
anaerobically)._

1. Plug and sterilise test-tubes 20 x 2 cm.

2. Kill a small rabbit with chloroform vapour. Open the abdomen with
all aseptic precautions, remove kidneys and testicles and transfer to a
sterile glass dish. Cut up the organs with sterile scissors into small
pieces--say 4 millimetre cubes. The four organs should yield from 25 to
30 pieces of tissue.

3. Drop a small piece of sterile tissue into the bottom of each
sterilised tube.

4. Take a flask containing about 400 c.c.