STAINING. 157 
2. Dry. 
3. Heat. 
4, Stain. 
5. Rinse in water. 
6. Decolorize. 
4. Rinse in water. 
8. Double stain. 
9. Rinse in water. 
10. Dry. 
11. Mount in Canada balsam. 
What may be said concerning the first three steps of this process ? 
Tn choosing the material from which to make the smear, cheesy-looking 
particles, if present, should be taken. The smear is made as before 
described. The drying may be done by waving the specimen about in 
the air of the room, or in the heated air over a flame. The third step 
or heating is for the purpose of fixing the smear to the cover glass, and 
is done by passing it back and forth three times slowly through a 
flame. Care must be taken not to burn the specimen or cause it to 
turn brown by too much heat or else it will not take the stain. 
What is the most convenient stain to use and how is it used ? 
The Ziehl carbol-fuchsin is the most convenient. To use it place 
some of the dye in a shallow dish, float the prepared cover glass, 
specimen side down, upon it, let it stand five or six hours at the tem- 
perature of the room and the staining will be complete. A quicker 
way is to float the specimen upon some of the dye in a watch glass, and 
apply just enough heat to cause it to steam, but not boil. This takes 
about fifteen minutes to stain. Another and still quicker method is 
to take the cover glass with the specimen side up in a pair of forceps, 
and pour a few drops of the staining solution upon it. It is now held 
so that the flame of an alcohol lamp or Bunsen burner just touches the 
under side of the glass. The solution is allowed just to come to a boil. 
This may be repeated once or twice, but care must be taken that the 
staining solution does not dry up. After heating in this way the 
specimen is thrown into clean water to rinse off the excess of dye. 
How is the specimen decolorized ? ‘ 
By dipping into a solution of nitric acid 1 part, water 4 parts, for 
an instant until all color has disappeared, rinsing at once in water and 
completing the process in strong alcohol. 
