HANGING-BLOCK CULTURE 235 



Hanging-block Culture (Hill). 



Apparatus required: As for hanging-drop cultivation 

 with the addition of a scalpel. 



Carry out the method as far as possible under cover 

 of a bell glass, to avoid aerial contamination. 



1. Liquefy a tube of nutrient agar (or gelatine) and 

 pour into a Petri dish to the depth of about 4 mm. and 

 allow to set. 



2. With a sharp scalpel cut out a block some 8 mm. 

 square, from the entire thickness of the agar layer. 



3. Raise the agar block on the blade of the scalpel 

 and transfer it, under side down, to the centre of a 

 sterile slide. 



4. Spread a drop of fluid cultivation (or an emulsion 

 of growth from a solid medium) over the upper surface 

 of the agar block as if making a cover-slip film. 



5 . Place the slide and block covered by the bell glass 

 in the incubator at 37 C. for ten minutes to dry 

 slightly. 



6. Take a clean dry sterile cover- slip in a pair of for- 

 ceps, and with the help of a second pair of forceps lower 

 it carefully on the inoculated surface of the agar (avoid- 

 ing air bubbles) , so as to leave a clear margin of cover- 

 slip overlapping the agar block. 



7. Invert the preparation and with the blade of the 

 scalpel remove the slide from the agar block. 



8. With a platinum loop run a drop or two of melted 

 agar around the edges of the block. This solidifies at 

 once and seals the block to the cover-slip. 



9. Prepare a sterile hanging-drop slide, and smear 

 hard vaseline or melted white wax on the rim of the 

 metal cell. 



10. Invert the cover-slip with the block attached on 

 to the hanging-drop slide, and seal the cover-slip firmly 

 in place. 



11. Observe as for hanging-drop cultivations. 



