. In the "fixed" condition (i. e., fixed, killed,
and stained by suitable methods).

The preparation of a specimen from a tube cultivation for examination by
these methods may be described as follows:

~1. Living, Unstained.~--(a) _"Fresh" Preparation._--

1. Clean and dry a 3 by 1 glass slip and place it on one of the squares
of filter paper. Deposit a drop of water (preferably distilled) or a
drop of 1 per cent. solution of caustic potash, on the centre of the
slip, by means of the platinum loop.

[Illustration: FIG. 68.--Holding tubes for removing bacterial growth, as
seen from the front.]

TECHNIQUE OF OPENING AND CLOSING A CULTURE TUBE.

2. Remove the tube cultivation from its rack or jar with the
left hand and ignite the cotton-wool plug by holding it to
the flame of the Bunsen burner. Extinguish the flame by
blowing on the plug, whilst rotating the tube on its long
axis, its mouth directed vertically upward, between the
thumb and fingers. (This operation is termed "flaming the
plug," and is intended to destroy any micro-organisms that
may have become entangled in the loose fibres of the
cotton-wool, and which, if not thus destroyed, might fall
into the tube when the plug is removed and so accidentally
contaminate the cultivation.)

3. Hold the tube at or near its centre between the ends of
the thumb and first two fingers of the left hand, and allow
the sealed end to rest upon the back of the hand between the
thumb and forefinger, the plug pointing to the right. Keep
the tube as nearly in the horizontal position as is
consistent with safety, to diminish the risk of the
accidental entry of organisms (Fig. 68).

4. Take the handle of the loop between the thumb and
forefinger of the right hand, holding the instrument in a
position similar to that occupied by a pen or a paint-brush,
and sterilise the platinum portion by holding it in the
flame of a Bunsen burner until it is red hot. Sterilise the
adjacent portion of the aluminium handle by passing it
rapidly twice or thrice through the flame. After sterilising
it, the loop must not be allowed to leave the hand or to
touch against anything but the material it is intended to
examine, until it is finished with and has been again
sterilised.

5. Grasp the cotton-wool plug of the test-tube between the