tage onward
the process is varied slightly for each particular bacterium.

~I. The Coli-typhoid Group.~--

~II. Streptococci.~--

~III. Bacillus Anthracis.~--

~IV. Bacillus Tetani.~--

The methods adopted for the isolation of these organisms are identical
with those already described under water (page 437 _et seq._).

~V. Bacillus Oedematis Maligni.~--Method precisely similar to that
employed for the B. tetani.

~VI. The Nitrous Organisms.~--

1. Take ten tubes of Winogradsky's solution No I (_vide_ page 198) and
number them consecutively from 1 to 10.

2. Inoculate each tube with varying quantities of the material as
follows:

To tube No. 1 add 1.0 c.c. of the soil water.
To tube No. 2 add 0.1 c.c. of the soil water.
To tube No. 3 add 1.0 c.c. from Capsule I.
To tube No. 4 add 0.1 c.c. from Capsule I.
To tube No. 5 add 1.0 c.c. from Capsule II.
To tube No. 6 add 0.1 c.c. from Capsule II.
To tube No. 7 add 1.0 c.c. from Capsule III.
To tube No. 8 add 0.1 c.c. from Capsule III.
To tube No. 9 add 1.0 c.c. from Capsule IV.
To tube No. 10 add 0.1 c.c. from Capsule IV.

Label and incubate at 30 deg. C.

~VII. The Nitric Organisms.~--

3. Take ten tubes of Winogradsky's solution No II, number them
consecutively from 1 to 10 and inoculate with quantities of soil water
similar to those enumerated in section VI step 2. Label and incubate at
30 deg. C.

4. Examine after twenty-four and forty-eight hours' incubation. From
those tubes that show signs of growth make subcultivations in fresh
tubes of the same medium and incubate at 30 deg. C.

5. Make further subcultivations from such of those tubes as show growth,
and again incubate.

6. If growth occurs in these subcultures, make surface smears on plates
of Winogradsky's silicate jelly (_vide_ page 198).

7. Pick off such colonies as make their appearance and subcultivate in
each of these two media.

TESTING FILTERS.

Porcelain filter candles are examined with reference to their power of
holding back _all_ the micro-organisms suspended in the fluids which are
filtered through them, and permitting only the passage of germ-free
filtrates. In order to determine the freedom of the filter from flaws
and cracks which would permit the passage of bacteria no matter how
perfect the general structure of the candle might be, the candle must
first be attached by means of a long piece of pressure tubing, to a
powe