MICRO-ORGANISMS. Dtf 



Watson Cheyne recommended that the sections, after stain- 

 ing in the Fuchsine Aniline Water, should be transferred to 

 Distilled Water, rinsed in Alcohol and placed in the following 

 contrast stain for one or two hours: Saturated Alcoholic 

 Solution of Methylene Blue, 20 cc. ; Distilled Water, 100 cc. ; 

 Formic Acid (sp. gr. 1-2), 1 cc. 



Ziehl Neelsen Method. 



This method is applicable for staining the bacilli of tubercle 

 and leprosy, and at the same time affords a diagnostic sign, 

 for these are the only micro-organisms that can retain the 

 stain after treatment with acid. 



The sections are removed from weak Spirit into Neelsen's 

 stain (Carbolic Fuchsine) (p. 59) for 10 or 15 minutes; then 

 decolourised in Sulphuric or Nitric Acid (p. 62), rinsed in 

 60 p. c. Alcohol and washed in a large volume of Water, to 

 remove the Acid. 



Nitric Acid is apt to contain considerable traces of Nitrous 

 Acid, which has a bleaching action on f uchsine-stained bacilli. 

 Where this is suspected it is better to use Sulphanilic Nitric 

 Acid (p. 62), the Sulphanilic Acid destroying any free Nitrous 

 Acid that may be contained in the Nitric Acid. 



For counterstaining, the sections may be treated as de- 

 scribed for nuclear staining with Methyl Green or Methylene 

 Blue (p. 36). 



Dehydrate in Absolute Alcohol, clear in Cedar Oil, and 

 mount in Balsam. 



Kuhne's Method. 



Place sections for 10 minutes in Carbolic Fuchsine; 

 thoroughly rinse in water; decolourise in Fluorescine Alcohol; 

 then transfer to Ethereal Oil, Xylol and Balsam ; or, to coun- 

 terstain before mounting, sections may be transferred for 5 to 

 10 minutes into Methyl Green Aniline Oil, diluted with half its 



