HANGING-DROP PREPARATIONS. 



75 



culture, a loop of the liquid is placed on the middle of the 

 under surface of the sterile cover-glass, which is held in 

 forceps, the points of which have been sterilised in a Bunsen 

 flame. If the organism be growing in a solid medium, an 

 eyelet of sterile bouillon is placed on the cover-glass in the 

 same position, and a very small quantity of the culture 

 (picked up with a platinum needle) is rubbed up in the 

 bouillon. The cover is then carefully lowered over the cell 

 on the slide, the drop not being allowed to touch the wall 

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



FIG. 26. 



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

 B. Another form of slide for similar cultures. 



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 

 plate (an ordinary glass plate used for plate cultures is 

 convenient). The drop is then placed on its upper 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 



