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TUBERCUL OSIS.                          213

Anilin,                                                             4,

Saturated alcoholic solution of gentian violet,   n,
Water,                                                           100,

and placed in an incubator or a paraffin oven, and kept
for twenty-four hours at about the temperature of the
body. When removed from the stain they are washed
momentarily in water, and then alternately in 25-33
per cent, nitric acid and 60 per cent, alcohol, until the
blue color of the gentian violet is almost entirely lost.
It must be remembered that the action of the strong acid
is a powerful one, and that too long a time must not be
allowed for its application. A total immersion of thirty
seconds is quite enough in most cases. After final thor-
ough washing in 60 per cent, alcohol the specimen is
counter-stained in a dilute aqueous solution of Bismarck
brown or vesuvin. The excess of stain is then washed
off in water, and the specimen is dried and mounted in
balsam. The tubercle bacilli will appear of a fine dark
blue, while the pus-corpuscles, epithelial cells, and other
bacteria, having been decolorized by the acid, will be
colored brown by the counter-stain.

This method, requiring twenty-four hours for its com-
pletion, is naturally one which has fallen into disuse for
practitioners who desire in the briefest possible time to
know simply whether bacilli are present in the sputum
or not.

Among clinicians Ziehl's method with carbol-fuchsin
has met with great favor. After having been spread,
dried, and fired, the cover-glass is held in the bite of an
appropriate forceps (cover-glass forceps), and the stain1
dropped upon it from a pipette. As soon as the entire
cover-glass is covered with stain it is held over the flame
of a spirit-lamp or a Bunsen burner until the stain begins
to volatilize a little, as indicated by a white vapor. When

1 Carbol-fuchsin (see p. 86):

Fuchsin,                                                              I;

Alcohol,                                                             10;