70 METHODS OP CULTIVATION OF BACTEKIA 



the wall or the edge of the cell. The edge of the cover-glass is 

 covered with vaseline, and the preparation is then complete and 

 may be placed under the microscope. If necessary, it may be first 

 incubated and then examined on a warm stage. (2 ) The sterile 

 cover-glass is placed on a sterile glass plate. The drop is then 

 placed on its topper surface, the details being the same as in the 

 last case. The edge of the cell in the slide is then painted with 

 vaseline, and the slide, held with the hollow surface downwards, 

 is lowered on to the cover-glass, to the rim of which it of course 

 adheres. The slide with the cover attached is then quickly 

 turned right side up, and the preparation is complete. 



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



^ ^z^^^^^^^^ ^^^ ^z^^^szzz zzzz^ 



a w;;///ss///;;;////s///,>? ^ z^r 7,,.'/,;, / >s//;»;7 77777m 



Fig. 25. 



A. Hollow-ground slide for hanging-drop cultures, shown in plan and section. 

 B. Another form of slide for similar cultures. 



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. It is sometimes 

 convenient for the observation of the growth of bacterial colonies 

 or of fungi to make hanging-drop cultures with a solid medium. 

 This can be done by substituting a drop of melted gelatin 

 or agar for bouillon and inoculating the surface after solidi- 

 fication. The method of microscopic examination is described 

 on page 89. 

 The Bacteriological Examination of the Blood. — A fairly 



