ase of sterile capsules (25 c.c. capacity).
Case of sterile graduated pipettes, 10 c.c.
(in tenths of a cubic centimetre).
Case of sterile graduated pipettes, 1 c.c.
(in tenths of a cubic centimetre).
Flask containing 250 c.c. sterile bouillon.
Tall cylinder containing 2 per cent. lysol solution.
Plate-levelling stand.
Case of sterile plates.
Tubes nutrient gelatine or gelatine agar.
Tubes of wort gelatine.
Tubes of nutrient agar.
Water-bath regulated at 42 deg. C.
Bunsen burner.
Grease pencil.

METHOD.--

1. Arrange four sterile capsules in a row; number them I, II, III, and
IV.

2. Fill 9 c.c. sterile bouillon into the first, and 9.9 c.c. bouillon
into each of the three remaining capsules.

3. Remove 1 c.c. milk from one of the bottles by means of a sterile
pipette and add it to the bouillon in capsule I; mix thoroughly by
repeatedly filling and emptying the pipette.

4. Remove 0.1 c.c. of the milky bouillon from capsule I, add it to the
contents of capsule II, and mix as before.

5. In like manner add 0.1 c.c. of the contents of capsule II to capsule
III; and then 0.1 c.c. of the contents of capsule III to capsule IV.

Then 1 c.c. of dilution I contains 0.1 c.c. milk sample.
1 c.c. of dilution II contains 0.001 c.c. milk sample.
1 c.c. of dilution III contains 0.00001 c.c. milk sample.
1 c.c. of dilution IV contains 0.0000001 c.c. milk sample.

6. Melt the gelatine and the agar tubes in boiling water; then transfer
to the water-bath and cool them down to 42 deg. C.

7. Number the gelatine tubes consecutively 1 to 12.

8. Inoculate the tubes with varying quantities of the material as
follows:

To tube No. 1 add 1.0 c.c. of the milk sample.
2 add 0.1 c.c. of the milk sample.
{ 3 add 1.0 c.c. from capsule I.
{ 4 add 0.1 c.c. from capsule I.
{ 5 add 1.0 c.c. from capsule II.
{ 6 add 0.1 c.c. from capsule II.
{ 7 add 0.5 c.c. from capsule III.
{ 8 add 0.3 c.c. from capsule III.
{ 9 add 0.2 c.c. from capsule III.
{ 10 add 0.5 c.c. from capsule IV.
{ 11 add 0.3 c.c. from capsule IV.
{ 12 add 0.2 c.c. from capsule IV.

9. Pour plates from the gelatine tubes; label, and incubate at 20 deg. C.

10. Liquefy five wort gelatine tubes