dle, and the subsequent emulsion of the bacterial
residue remaining on the walls of the candle with a small measured
quantity of sterile bouillon.

A. ~Enrichment Method.~

(Dealing with the demonstration of bacteria of intestinal origin.)

_Apparatus Required_ (_Preliminary Stage_):

Incubator running at 42 deg. C.
Case of sterile pipettes, 1 c.c. graduated in tenths.
Case of sterile pipettes, 10 c.c. graduated in c.c.
Case of sterile pipettes, graduated to deliver 25 c.c.
Tubes of bile salt broth (_vide_ page 180).
Flask of double strength bile salt broth (_vide_ page 199).
Tubes of litmus silk.
Sterile flasks, 250 c.c. capacity.
Buchner's tubes.
Tabloids pyrogallic acid.
Tabloids sodium hydrate.
Bunsen burner.
Grease pencil.

(_Later stage_):

Incubator running at 37 deg. C.
Surface plates of nutrose agar (see page 232).
Aluminium spreader.
Tubes of various media, including carbohydrate media.
Agglutinating sera, etc.

METHOD.--

1. Number a set of bile salt broth, tubes 1-5, and a duplicate set
1a-5a.

2. Number one flask 7 and another 8.

3. To Tubes No. 1 and 1a add 0.1 c.c. water sample.

To Tubes No. 2 and 2a add 1 c.c. water sample.

To Tubes No. 3 and 3a add 2 c.c. water sample.

To Tubes No. 4 and 4a add 5 c.c. water sample.

To Tubes No. 5 and 5a add 10 c.c. water sample.

4. Put up all the tubes in Buchner's tubes and incubate anaerobically at
42 deg. C.

NOTE.--The bile salt medium is particularly suitable for the
cultivation of bacteria of intestinal origin, and at the
same time inhibits the growth of bacteria derived from other
sources.

The anaerobic conditions likewise favor the multiplication of intestinal
bacteria, and also their fermentative activity. The temperature 42 deg. C.
destroys ordinary water bacteria and inhibits the growth of many
ordinary mesophilic bacteria.

5. Pipette 25 c.c. of double strength bile salt broth into flask 6, and
50 c.c. double strength bile salt broth into flask 7.

6. Pipette 25 c.c. water sample into flask 6, and 50 c.c. water sample
into flask 7.

7. Incubate the two flasks aerobically at 42 deg. C.

8. After twenty-four hours incubation note in each culture:

a. The presence or absence of visible growth.

b. The reaction of the medium as indicated by the colour change, if
any, the litmus has undergone.

c. The presence or absence of ga