AGf~ICULTURAL RESEARCH, PUSA.

STAINING METHODS 149
the top of the Bunsen flame for a few seconds so that
the slide becomes hot. Care must be taken not to
char the film, and when the slide is just too hot to be
borne on the back of the hanel, fixation is complete.
Films on cover-slips require a minimum of time for
fixing owing to the thinness of the glass. The covcrslips
may be held by means of Comet's forceps.
With solid material, such as cultures on agar, etc.,
it is necessary to place a loopful of clean "IJater on the
slide. The loop is t.hen sterilised and a minute quantity
of material, obtained by just touching the growth, is
transferred to the drop, thoroughly emulsified, and
the mixture is spread evenly on the slide. The resulting
film is fixed and dried as above. Beginners are
very apt to take more material than necessary from
the cultnrc and thus make too thick jilms_
STAINING
The method of staining varies with the nnture of
the prcparation (film or section).
FILMS
'fhe stains arc poured directly or filtered on to the
slide. W hen staining is completed, the dye is washed
off with water and the slide is allowed to dry in the
vertical position or is placed between two sheets
of 'white fluftless blotting-paper or filter paper. The
drying of the film is completed over the Bunsen name.
Such stained films may be monnted in Canada balsam
under a cover-slip, or may be examined ulllllounted
with the oil-immcrsion lens, a small drop of eedarwood
oil being placed directly on the film. If it is
desired to mouut the preparation later, the oil can
be removed with xylol.
TISSUE SECTIONS
. The scetions being embedded in parafllll (1,idc p.177),
it is neeessary to rentoye the paraffin so that a watery
stain may penetrate. 1'he paraffm is first removed