76 METHODS OF CULTIVATION OF BACTERIA. 



course adheres. The slide with the cover attached is then 

 turned right side up, and the preparation is complete. 



In the case of B the drop of fluid is placed on the 

 centre of the table x. The drop must be thick enough to 

 come in contact with the cover-glass when the latter is 

 lowered on the slide, and not large enough to run over 

 into the surrounding trench y. The cover-glass is then 

 lowered on to the drop, and vaseline is painted along the 

 margin of the cover-glass. The method of microscopic 

 examination is described on page 94. 



Anarobic Hanging -drop Cultures. The growth and 



/ cf 



FiG. 27. Graham Brown's chamber for anaerobic hanging-drops. 



examination of bacteria in t hanging-drops under anaerobic 

 conditions involve considerable difficulty, but may be carried 

 out in an apparatus devised by Graham Brown (Fig. 27). 

 It consists of two brass plates (a and a') which can be 

 approximated by screws, and which have two rounded 

 apertures in their middle f in. in diameter. These support 

 two rubber rings, an upper thinner one (^) and a lower 

 thick one (*/), their inner diameter being the same as that 

 of the apertures in the plates. Between b and d is placed 

 a stout cover-glass of suitable size (c) ; d is separated from 

 the plate a by a square plate of glass (e) (a portion of an 

 ordinary glass-slide for microscopical purposes does well). 

 Two small metal tubes (/) are inserted through the rubber d. 



