AGf~ICULTURAL RESEARCH, PUSA.

STAINING lIlETIIODS ] ,IHl
li'ilms.-Smcars arc made, dried and fixed in the
usual manner:
(1) Flood the slide with filtered carbol fuchsin and
heat until steam rises. Allow the preparation
to stain for five minutes, heat being applied
at intervals to keep the stain hot. The stain
must not he allowed to evaporate and dry on
the slide.
(2) Wash with water.
(3) Immerse the slide in 20 per cent. sulphuric acid.
'rhe red colour of' the preparation is changed
to yellowish brown. Arter about a minute in
the acid rerllove the slide, wash with water
and place it in the acid again. This process
should be repeated several times. The object
of the washing is to remove the compound of
acid with stain and allow fresh acid to gain
access to the preparation. The decolorisation
is finished when, after washing, the smear is a
faint pink.
(,1) Wash the slide well in water.
(5) Treat with 95 per cent. alcohol for two minutes.
(6) Wash with water.
(7) Counter-stain with Lamer's methvlene blue or
dilute malachite green for tCll to tEirt.y se('(tnds.
(8) Wash, blot, dry and mount.
Acid-fast bacilli stain bright rcd, while the tissue
cells and othcr organisms are stained blue.
Other organisms are" acid-fast" in addition to the tubercle
bacillus. The most important in diagnostic work is the smegma
bacillus, which is frequently found in samples of urine. Treatment
with spirit in addition to acid may, however, decolorise
this type of organism, whereas the tubercle bacillus is both
acid- and alcohol-fast. The decolorisation with spirit is therefore
important when examining urine for the prcsencc of the
tubercle bacillus.
It should be notefl that in filmR staine(l by Ziehl-Neelsell's
method, red-stained organisms in the midst of hyaline material
must not be regarded as tubercle bacilli, as SUell material may
be resistant to decolorisation.