s formation, as indicated by a froth
on the surface of the medium, and the collection of gas in the inner
"gas" tube.

9. Replace those tubes which show no signs of growth in the incubator.
Examine after another period of twenty-four hours (total forty-eight
hours incubation) with reference to the same points.

10. Remove culture tubes which show visible growth from the Buchner's
tubes, whether acid production and gas formation are present or not.

11. Examine all tubes which show growth by hanging-drop preparations.
Note such as show the presence of chains of cocci.

12. Prepare surface plate cultivations upon nutrose agar from each tube
that shows growth either macroscopically or microscopically, and
incubate for twenty-four hours aerobically at 37 deg. C.

13. Examine the growth on the plates either with the naked eye or with
the help of a small hand lens. Practice will facilitate the recognition
of colonies of the coli group, the typhoid group and the paratyphoid
group; also those due to the growth of streptococci. The investigation
from this stage proceeds along two divergent lines of enquiry--the first
being concerned with the identity of the bacilli--typhoid bacilli, the
second with that of the cocci.

A. _B. Coli and its allies._

14. Pick off coliform or typhiform colonies; make streak or smear
subcultivations upon nutrient agar; incubate aerobically for twenty-four
hours at 37 deg. C.

15. Examine the growth in each tube carefully both macroscopically and
microscopically. If the growth is impure, replate on nutrose agar, pick
off colonies and subcultivate again. When the growth in a tube is pure,
add 5 c.c. sterile normal saline solution or sterile broth, and emulsify
the entire surface growth with it.

16. Utilise the emulsion for the preparation of a series of
subcultivations upon the media enumerated below, using the ordinary loop
to make the subcultures upon solid media, but adding one-tenth of a
cubic centimetre of the emulsion to each of the fluid media by means of
a sterile pipette.

Gelatine streak.
Agar streak.
Potato.
Nutrient broth.
Litmus milk.
Dextrose peptone solution.
Laevulose peptone solution.
Galactose peptone solution.
Maltose peptone solution.
Lactose peptone solution.
Saccharose peptone solution.
Raffinose peptone solution.
Dulcite peptone solution.
Mannite peptone solution.
Glycerin peptone solution.
Inu