ne 1 gramme
Iodide of potassium 3 grammes
In distilled water 300 c.c.

5. Wash in water.

6. Wash with alcohol until no more colour is discharged and the alcohol
runs away clear and colourless.

The following mixture may be substituted for absolute alcohol as a
decolouriser

Acetone 10 c.c.
Absolute alcohol 100 c.c.

7. Wash in water.

8. Counterstain very lightly with aqueous solution of Neutral Red. Other
counterstains may be used such as dilute eosin, dilute fuchsin, or
vesuvin.

NOTE.--This section may be omitted when dealing with films
prepared from pure cultivations.

9. Wash in water.

10. Dry and mount.

~Gram-Claudius Method.~--

1. Prepare a cover-slip film and fix in the usual way.

2. Stain in methyl violet, 1 per cent. aqueous solution for three to
five minutes.

3. Treat with two lots picric acid, saturated aqueous solution.

4. Wash in water and dry.

5. Decolourise with clove oil.

6. Wash off clove oil with xylol.

7. Mount in xylol balsam.

~Gram-Weigert Method.~--

1-5. Proceed as for the corresponding sections of Gram's method (_quod
vide_).

6. Dry in the air.

7. Wash in aniline oil, 1 part, xylol, 2 parts, until no more colour is
discharged.

8. Wash in xylol.

9. Mount in xylol balsam.

~Modified Gram-Weigert Method.~--(To demonstrate trichophyta in hair.)

1. Soak the hairs in ether for ten minutes to remove the fat.

2. Stain thirty minutes in a tar-like solution of aniline gentian violet
(prepared by adding 15 drops of the alcoholic solution of gentian violet
to 3 drops of aniline water).

3. Dry the hairs between pieces of blotting paper.

4. Treat with perfectly fresh iodine solution.

5. Again dry between blotting paper.

6. Treat with aniline oil to remove excess of stain. (If necessary, add
a drop or two of nitric acid to the oil.)

7. Again treat with aniline oil.

8. Treat with aniline oil and xylol, equal parts.

9. Clear with xylol.

10. Mount in xylol balsam.

To obtain the best differentiation the preparation should be repeatedly
examined microscopically (with a 1/6-inch objective) between steps 5 and
9, as the actual time involved varies with different specimens.

~Ziehl-Neelsen's Method.~--(To demonstrate tubercle and other acid-fast
bacilli.)

1. Smear a thin, even film of the specimen on the cover-slip by means of
the platinum loop. (In the case of sputum,