47 



mordant. Curiously enough the value of each of these 

 methods seems to rest largely in the individual using them, 

 as some workers succeed with one method while others fail 

 with it but obtain excellent results with one of the other 

 processes. Although the flagella are thought to be the 

 organs of locomotion they do not seem to be of any special 

 morphological value in differentiating closely related species. 

 They are, however, elements in the structure of motile bac- 

 teria and their demonstration is much to be desired. 



70. General directions. Make a cover-glass prepara- 

 tion from the growth on the agar culture of Bacillus cholerae 

 suis made in Exercise XVII and stain it with carbol fuchsin. 

 Preserve this to compare with preparations stained for the 

 purpose of demonstrating the flagella. 



Clean about 20 cover-glasses after the special method for 

 flagella staining (4). Make about 10 cover-glass prepar- 

 ations on these from the agar culture and stain for flagella. 

 Use LoefHer's method but if it does not succeed the second 

 process may be tried. 



71. Making cover-glass preparations for flagella 

 stain. Place 2 loopfuls of sterilized, distilled water 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 to dry. The bacteria become 

 disseminated throughout the water by means of their power 

 of locomotion. When dry they are ready for the staining 

 treatment. 



72. Staining the flagella by Loeffler's method. The 

 bacteria are fixed to the cover-glasses by holding them, film 

 upward, between the thumb and fore finger, over a gas flame 



