64 MICRO-ORGANISMS. 



For Living Bacteria. 



The fluid under examination is mixed on the slide with a 

 drop of an aqueous (free from Alcohol) solution of Gentian 

 Violet, Fuchsine, or Methylene Blue. 



For Tissues and Cover-glass Preparations. 



Stain for a few minutes in the Gentian-Violet Aniline- 

 Water (p. 58) ; wash in water, and all but decolourise the 

 ground substance in strong Alcohol ; counterstain, if re- 

 quired, and mount as usual. 



Gram's Method. 



Sections are removed from weak Alcohol, and placed in 

 Gentian- Violet Aniline- Water for 1 to 3 minutes. (Tubercle 

 sections 12 to 24 hours.) 



The sections are quickly rinsed in Absolute Alcohol and 

 transferred into Gram's solution (p. 61), until they acquire 

 a brown colour; this takes about 1 to 3 minutes. The 

 sections are then washed in 90 p. c. Alcohol until they 

 are a pale yellow, dehydrated, cleared, and mounted in 

 Balsam. 



The sections are frequently counterstained with Eosine or 

 Vesuvine. 



Weigert's Modification of Gram's Method. 



As the prolonged washing in Alcohol may remove colour 

 from the organisms, Weigert proposed the substitution of 

 Aniline for Alcohol, and conducts the process on a slide. 

 Place the section on a glass slide, and stain it with a few 

 drops of Gentian- Violet Aniline-Water ; remove the excess 

 of fluid, and apply for 2 minutes a few drops of Gram's solu- 

 tion. Eemove this by gently blotting it off ; then wash the 

 section by allowing Aniline to flow gently backwards and 

 forwards over it'; when no more colour comes away, pour off 



