16 BACTERIA: FORMS AND REPRODUCTION 



Ex. 11. Staining of Flagella. The flagella or motile organs 

 of bacteria are of extraordinary fineness and delicacy, and 

 appear to dissolve or become thrown off and disorganized 

 when the water in which the bacteria are living dries up. 



Under certain conditions they may be rendered visible by 

 staining, but the operation is one of much difficulty and 

 uncertainty. The chief elements of success are extreme clean- 

 liness of the cover-glasses on which the organisms are placed, 

 and a culture of the bacteria in the right state of development, 

 the best results being obtained from growths eight to sixteen 

 hours old upon an agar medium. 



Various staining methods have been devised, those of Loeffler 

 and Van Ermengem being as useful as any. 



Loeffler's Method. 



(1) Take an absolutely clean slide, cleaned as in Ex. i ; 

 wipe it with a clean handkerchief, and handle it with the 

 fingers as little as possible. Place upon it three small drops 

 of water. 



(2) With a fine platinum loop remove a small portion of a 

 six to eighteen hours old agar culture of Bs. subtilis, Bact, 

 (Proteus] vulgare, or other motile species, and place it in the 

 first drop of water : this will become slightly turbid. Now 

 pass the platinum loop through the flame, and, when cool 

 transfer a part of the first drop to the second on the slide ; in 

 the same way add a small part of the second to the third drop. 

 By diluting in this manner the bacteria become separate from 

 each other. 



(3) Take one or two absolutely clean cover-glasses. Now dip 

 the end of a platinum needle, the top of which has been bent at 

 right angles, into the third drop, and with one stroke gently rub 

 the water which adheres to it on to the surface of the cover- 

 glass ; repeat the operation on another part of the cover-glass. 

 Dry the cover-glass in an incubator at 37C. for three or four 

 minutes. The dilutions, spreading of the drops and smears, and 



