84 MICROSCOPIC EXAMINATION OF BACTERIA. 



which is suspected of being tubercular. Nothing but the 

 needle should come in contact with it, and as soon as there is 

 no further use for it it should be covered with a 5 per cent, 

 carbolic acid solution or milk of lime. The inoculating 

 needle should be sterilized immediately after use, and like- 

 wise anything else that may have come in contact with the 

 suspected material. The film is dried in the air and fixed in 

 the flame before staining : 



Ehrlich-Weigert method: Float the cover-glass, film side 

 down, in a watch-crystal containing anilin methylene-violet ; 

 or immerse the cover-glass film side up. Heat until the stain 

 begins to steam ; then set it aside for two or three minutes. 

 Remove the specimen from the stain and decolorize in 1 part 

 of nitric acid and 3 of distilled water. Hold the cover-glass 

 with the forceps and move it gently to and fro for a few 

 seconds. Wash in 60 per cent, alcohol and then in water. 

 If a contrast-stain is wanted, cover the film for a few minutes 

 with a saturated solution of vesuvin. Wash, dry, and mount 

 in Canada balsam. The tubercle bacillus is stained violet or 

 purple, and all the other organisms, as well as the mucus, are 

 stained a light brown. 



Friedlaender method: The stain used in this method is 

 known as ZiehPs solution. It consists of: 



Fuchsin, 1 gram ; 



Alcohol, 10 c.c. 



Dissolve, and add 100 c.c. of a 5 per cent, solution of 

 carbolic acid. 



Cover the smear with this stain and heat gently until steam 

 is given off". Decolorize with : 



Nitric acid, 5 c.c. ; 



Alcohol (80 per cent.), 95 " 



and counter-stain with methylene-blue. Wash in distilled 

 water, dry, and mount in Canada balsam. The tubercle 

 bacillus is stained a bright red, everything else blue. 



Gabbett method : This is an exceedingly simple method, 



