62 LABORATORY BACTERIOLOGY 
Saturated alcoholic solution of methyl violet, basic fuchsin, 
or methylene blue can be substituted for gentian violet in the 
above formula with equally good results. 
93. Staining the flagella by Loeffler’s method. Place 2 loop- 
fuls of sterilized distilled water or normal salt solution on the 
center of the cover glass. Gently touch the surface growth 
on the agar culture with the end of the platinum needle and 
immerse it in the water on the cover glass without spreading 
the drop. The impregnated needle should carry bacteria 
enough for 3 or 4 preparations. Then place the tray of cover 
glasses in the incubator todry. The bactéria’ become dissemi- 
nated throughout the water by means of their power of loco- 
motion. When dry they are ready for the staining treatment. 
The bacteria are fixed to the cover glass by holding them, 
film upward, between the thumb and forefinger, over a gas 
flame for about aminute. They are then treated with Loeffler’s 
mordant. 
Place the fixed cover-glass preparation in a large test tube, 
cover it with the mordant, and carefully heat over a gas flame 
or in a water bath until steam is given off. Allow the mordant 
to act for from 3 to 5 minutes. Then remove the cover glass 
with a bent wire loop and fine forceps and thoroughly rinse it 
in water. Then place it in a similar tube and cover with 
carbol fuchsin for staining. Heat this as the mordant was 
heated and allow the stain to act for from 5 to ro minutes. 
Remove the cover glass as before and thoroughly rinse in water. 
If the stain is too deep, decolorize by rinsing the preparation 
for a few seconds in alcohol and again in water. It is then 
ready for the microscopic examination in water, or it may be 
allowed to dry and then be mounted in balsam. If the first 
preparation fails, add 2 drops of a 10% solution of sulphuric 
acid to the mordant. 
