96 PRACTICAL BACTERIOLOGY. 



the solutions may be warmed. After a drop has beea 

 placed upon the cover-glass, the latter may be care- 

 fully taken up with the forceps, and held over a low 

 flame until steam begins to be formed. It is then 

 withdrawn from the flame for a time, after which it is 

 heated again once or twice in a similar manner. The 

 liquid must on no account be allowed to boil, as, in 

 that case, stain precipitates are formed, which can only 

 be got rid of later on with great difficulty. If the 

 staining solution on one part of the cover-glass should 

 become dry, it is best to add a little more of the solu- 

 tion, and to apply heat for a moment, rather than to 

 try and wash off the dried up stain with cold water. 

 The cover-glass is then immediately rinsed in water, 

 the best plan being to hold it under a tap until no 

 more colour comes off. It is then laid on a slide, being 

 firmly pressed down upon it with the left thumb nail, 

 whilst it is dried with a soft linen cloth, after which 

 it can be examined with the microscope. When the 

 cover- glass is floated on the staining solution, which. 

 it is best to put in a flat porcelain dish, the latter is 

 held over a flame until clouds of steam rise up from, 

 it ; it should then be allowed to stand for about two 

 minutes, without being heated again ; the cover-glass 

 is then taken out with the forceps and treated as 

 before. 



In successful preparations the bacteria are stained a 

 deep red or violet, whilst the background is colourless. 



