ne
carefully.

5. Kill the second guinea-pig at the end of the second week and examine
carefully.

6. Utilise the remainder of the deposit for microscopical examination
and cultivations upon Dorset's egg medium.

NOTE.--No value whatever attaches to the result of a
microscopical examination for the presence of the B.
tuberculosis unless confirmed by the result of inoculation
experiments.

~6. Streptococcus Pyogenes Longus.~--

(A) 1. Spread serial surface plates upon nutrose agar. Also plant serial
cultivations upon sloped nutrient agar (six tubes in series).

2. If the resulting growth shows colonies which resemble those of the
streptococcus, make subcultivations upon agar and in bouillon, in the
first instance, and study carefully.

(B) 1. Plant a large loopful of the deposit D^{2} into each of three
tubes of glucose formate bouillon, and incubate anaerobically (in
Buchner's tubes) for twenty-four hours at 37 deg. C.

2. If the resulting growth resembles that of the streptococcus, make
subcultivations upon nutrient agar.

3. Prepare subcultivations of any suspicious colonies that appear, upon
all the ordinary media, and study carefully.

If the streptococcus is successfully isolated, inoculate serum bouillon
cultivations into the mouse, guinea-pig, and rabbit, to determine its
pathogenicity and virulence.

~7. Staphylococcus Pyogenes Aureus.~--

1. Examine carefully the growth upon the serial blood serum cultivations
prepared to isolate B. diphtheriae and the serial agar cultivations to
isolate streptococci after forty-eight hours' incubation.

2. Pick off any suspicious orange coloured colonies, plant on sloped
agar, and incubate at 20 deg. C. Observe pigment formation.

3. Prepare subcultivations from any suspicious growths upon all the
ordinary media, study carefully and investigate their pathogenicity.

~8. Micrococcus Melitensis.~--The milk from an animal infected with M.
melitensis usually contains the organisms in large numbers and but few
other bacteria.

1. Spread several sets of surface plates upon nutrose agar, each from
one loopful of the deposit in tube D^{1} or D^{2}.

2. Spread several sets of surface plates upon nutrose agar, each from
one drop of the original milk sample.

3. Incubate aerobically at 37 deg. C. and examine daily up to the end
of ten days.

4. Pick off suspicious colonies, examine them microscopically and
subcultivate upon nutrose agar in tu