n consists in:

(a) Inoculating a tube of sterile nutrient medium with a portion of
the material to be examined.

(b) Incubating the inoculated tube at a suitable temperature.

The details of the first of these processes must be varied somewhat
according to whether the tubes of nutrient media are inoculated or
"planted" from--

1. Pre-existing cultivations.

2. Morbid material previously collected (_vide_ page 373).

3. Fluids, tissues, etc., or from the animal body direct.

The method of preparing tube cultivations from pre-existing cultivations
is as follows:

[Illustration: FIG. 117.--Inoculating tubes, seen from the front.]

~1. Fluid Media~ (e. g., Nutrient Bouillon).--

1. Flame the cotton-wool plug of the tube containing the cultivation and
also that of the tube of sterile bouillon.

2. Hold the two tubes, side by side, between the left thumb and the
first and third fingers, allowing the sealed ends to rest on the dorsum
of the hand, and separating the mouths of the tubes (which are pointed
to the right) by the tip of the second finger. Keep the tubes as nearly
horizontal as is possible without allowing the fluid in the bouillon
tube to reach the cotton-wool plug (Fig. 117).

3. Sterilise the platinum loop and allow it to cool.[8]

4. Grasp the plug of the tube containing the cultivation between the
little finger and palm of the hand and remove it from the tube.

5. Grasp the plug of the bouillon tube between the fourth finger and the
ball of the thumb and remove it from the tube.

6. Pass the platinum loop into the tube containing the culture--do not
allow the loop to touch the sides of the tube, or the handle to touch
the medium--and remove a small portion of the growth; withdraw the loop
from the tube, keeping the infected side of the loop downward.

7. Pass the loop into the bouillon tube almost down to the level of the
fluid, reverse the loop so that the infected side faces upward, emulsify
the portion of the growth in the moisture adhering to the side of the
tube which is uppermost. Withdraw the loop.

8. Replug both tubes.

9. Sterilise the platinum loop.

10. Label the bouillon tube with (a) the name of the organism and
(b) the date of inoculation.

11. Incubate.

~2. Solid Media.~--Solid media are stored in tubes in one of two ways:

1. Oblique tube or slanted tube (Fig. 118), in which the medium has been
allowed to solidify whilst the tube was retained in an inclined
position