170 ATLAS OF BACTERIOLOGY. 



2. Bunge's mordant: 



25 c.c. of a twentyfold diluted officinal ferric chloride 



solution. 

 75 c.c. saturated watery solution of tannin. 



To this solution is added, immediately before using, 

 enougli of a three- per-cent solution of hydrogen per- 

 oxide to produce a reddish-brown color, and it is 

 then filtered (we have always dispensed with the 

 peroxide). 



D. Substances Used for Clearing Up and Mounting. 



1. Xylol. 



2. Canada balsam. 



3. Dammar varnish. 



3. PREPARATION OF STAINED SPECIMENS OF BACTERIA. 

 A. Smear Preparations. 



1. Ordinary Stain with Fuchsin or Methyl Blue. 

 This may be used for all bacteria with the exception 

 of the tubercle bacillus. 



We place upon the cover-glass or slide a loopful of 

 distilled water, mix with it a trace of pure culture 

 (best from a solid nutrient medium) and then spread 

 the drop in a very thin layer. After the fluid has 

 evaporated the preparation, with the layer turned up, 

 is rapidly drawn three times through the flame in 

 order to fix the bacteria on the glass (not to burn 

 them) and the layer of bacteria is covered with the 

 staining solution. After a brief interval (one minute), 

 perhaps after feebly warming the glass, the prepara- 

 tion is washed with water and allowed to dry (some- 



