10 PRACTICAL BACTERIOLOGY. 



Actual movement, where the bacteria swim or move 

 about in the suspending fluid. This last is what we 

 mean by motility of a bacterium. 



4. Make a hanging drop preparation from the 18 

 hours, broth culture of Bacillus typhosus supplied. 



(a) Transfer a drop of the culture to a clean cover 

 glass. (Never neglect aseptic precautions). 



(&) Ring about with vaseline, the depression on a 

 hollow ground slide. 



(c) Invert the cover glass over the cell and press 

 firmly into the ring of vaseline, so as to exclude the air. 



In examining the preparation find the edge of the 

 drop with the low dry power, then fixing the slide, 

 examine with the oil-immersion lens, partially closing 

 the diaphragm. 



5. In like manner examine the liquefied gelatine 

 culture of Staphylococcus pyogenes aureus. 



No motility is present, but Brownian movement can 

 be noted. 



Hanging Drop Cultures. 



Hanging drop cultures are used to study the manner 

 of division, the process of spore formation and germina- 

 tion, and the motility of bacteria. The three former 

 require continual microscopic observation of the culture 

 drop, at certain periods. 



6. Make hanging drop cultures of Bacillus anthracis 

 and of Streptococcus pyogenes. 



(a) Place cleansed cover glasses, sterilized by pass- 

 ing through the flame, on a strip of wire gauze, sterilized 



