in HANGING DROPS 15 



(e) With a straight sterilised platinum needle inoculate 

 two of the drops with a minimal trace of the Streptococcus 

 broth culture, and two with a minimal trace of Bacillus 

 filamentosus. 



(/) Now carefully place each cover-glass on the vaseline 

 ring around the hollow on the slide, the drop facing, of 

 course, downwards. 



(g) Gently press the cover-glass down on the vaseline, 

 so as to completely shut off all air from the chamber. 



(h) Place the slides in the warm or cold incubator, 

 according as broth (agar-agar) or gelatine is used. 



Examine the hanging drops after twenty-four hours 

 with a high power, using a narrow diaphragm. 

 In the one case there will be a pure culture of 

 streptococci, in the other a pure culture of filament 

 ous bacilli. 



Examination of Bacteria in a Hanging Drop 



To study the motility of micro-organisms, hanging drops 

 should be made. 



(a) Take an ordinary clean slide. 



(b) With a cork-borer cut a small ring -|- to |j- in. in 

 diameter out of filter-paper, four to eight layers thick. 



(c) Trim the perforated filter-paper so as to fit the slide, 

 moisten it with water, and place it on the centre of the 

 slide. 



(d) With a sterilised platinum loop place a drop of a fresh 

 broth culture of the Bacillus filamentosus on the centre of 

 a clean sterilised cover-glass. 



