84 Modern Microscopy. 



three times through the flame of a spirit-lamp ; this will 

 fix the albumen and fasten the bacteria to the glass. 



To stain Bacteria on Cover-Glasses. They should be 

 floated with the organisms downwards on a saturated 

 watery solution of any of the following anilin dyes : 

 Methyl blue, methyl violet, gentian violet, fuchsin, visuvin, 

 or Bismarck brown. From ten to fifteen minutes is enough 

 for the first four stains ; vesuvin and Bismarck brown re- 

 quire about an hour. When the staining is complete 

 wash the cover in distilled water ; if the colour is too deep 

 wash in a J per cent, solution of acetic acid, and then 

 again in water ; put away to dry. When quite dry add a 

 drop of Canada balsam, and mount on a slide in the usual 

 way. 



When bacteria are present in the organs of animals the 

 tissues should be hardened in methylated spirit for about 

 a week ; then cut very thin sections with a freezing micro- 

 tome. The sections may be stained in any of the above 

 dyes ; then wash in water, dehydrate in spirit, clear in 

 oil of cedar or bergamot, and mount in balsam. 



Ehrlich's Method for Double - staining. To 100 

 parts of a saturated watery solution of anilin oil add 11 

 parts of a saturated alcoholic solution of fuchsin, and filter. 

 Place the covers or sections in the stain in a watch-glass, 

 and warm slowly over a spirit-lamp until vapour rises. 

 Wash in water, and then immerse for about a minute in 

 dilute nitric acid, 1 part of acid to 2 parts water. Wash 

 again in water, and stain again in a solution of methyl 

 blue, 100 parts of distilled water to 20 parts of a saturated 

 solution of methylated blue in alcohol for about 20 minutes. 

 Wash in water, and in the case of sections dehydrate in 

 spirit, clear in oil of cedar or bergamot, and mount in 

 balsam. The cover-glasses must be dried, then add a drop 

 or two of balsam, and mount as above. The anilin oil 

 solution is made by adding the oil to distilled water ; shake 

 well, and let it stand for twenty-four hours before using ; 

 water will only take up about 3 per cent, of anilin oil. 



