Page 200 - My FlipBook

174 THE MICRO-OROANISMS OF THE HUMAN MOUTH.

experience, preferable; methyl-violet, methyleiie-blue, and ve-
suvin not quite so good. The staining Avith fuchsine is carried
out in the following manner : Enough of a concentrated alco-
holic solution of fuchsine is added to water to turn it cherry-red.
In this solution the sections are allowed to remain for three to
five minutes, and are then placed (after Gram's method) for one
to three minutes into a solution of iodine 1.0, iodide of potas-
sium 2.0, distilled water 300.0. Then they are put into absolute
alcohol, which must be renewed as soon as it becomes red. In
the alcohol the color gradually disappears from the tissue, while
the bacteria retain it. The sections must not be left in the alco-
hol too long, otherwise the bacteria will also give up a portion
of their coloring-matter. Some experience is necessary in order
to take out the cuts at the proper time. From the alcohol they
are transferred to oil of cloves, then mounted in Canada balsam.
By this method the parts infiltrated w^ith bacteria, or the bac-
teria themselves, are colored red ; everything else appears un-
stained.
I have obtained equally good, and, in fact, I have sometimes
thought, better, results by simply treating the slightly overstained
cuts with absolute alcohol, though the process is somewhat longer,
it sometimes requiring an hour or more to decolorize the prepara-
tions, during which time the alcohol must be repeatedly changed.
The preparations, when taken from the alcohol, must not show
a diftuse staining, but rather a difierential staining, some parts of
the preparation appearing to the naked eye quite colorless and
others bright red.
The other coloring-materials above mentioned are employed
in the same way as fuchsine. Eemarkably beautiful prepara-
tions may be obtained in a very few minutes by employing Giin-
ther's modification of Gram's method with gentian-violet.
The cuts are brought from absolute alcohol for one to two
minutes in a deep violet solution of gentian-violet in aniline
water, then removed on the point of a platinum wire, lightly
toucbed to bibulous paper to remove the excess of coloring solu-
tion, placed for two minutes in the iodine-iodide of potassium
solution, one-half minute in alcohol, ten seconds in 3 per cent,
alcoholic solution of hydrochloric acid, then again one to five