THE METHODS OF STAINING MICROBES 69 



drying for a few minutes, they are passed rapidly 

 (three or four times) through a Bunsen flame. To 

 stain the preparations they are allowed to float 

 (with the prepared side downwards) on the surface 

 of an aqueous solution of methyl violet, gentian 

 violet, or magenta, for a short time. After this the 

 cover-glasses are washed with water, then spirit, 

 and finally with sterilised distilled water. They 

 are then drained, dried, and mounted in Canada 

 balsam or any suitable medium. The preparation 

 must now be set aside to dry, and when thoroughly 

 dry it is ' ringed ' or sealed with Hollis' glue. 



Before continuing the description of the various 

 methods of staining, we describe the preparation of 

 several staining fluids : (1) Gentian violet stain is 

 prepared by rubbing 2 grammes of gentian violet in 

 a glass mortar with 10 cc. of alcohol (sp. gr., 0*83), 

 in which has been dissolved 2 cc. of aniline oil. To 

 this is added 90 cc. of distilled water ; (2) Koch's 

 methyl violet stain contains the following ingre- 

 dients: Aniline water, 100 cc. ; an alcoholic solu- 

 tion of methyl violet, 11 cc. ; and absolute alcohol, 

 10 cc. ; (3) the stain known as Bismarck brown is 

 prepared by dissolving 2 grammes of Bismarck 

 brown in 15 cc. of alcohol, and then adding 85 cc. 

 of distilled water ; (4) haematoxylin solution con- 

 tains 2 grammes of haematoxylin, 2 grammes of 

 alum, and 100 cc. each of alcohol, glycerine, and 

 distilled water; (5) the methylene blue stain is 

 prepared by dissolving 2 grammes of methylene 

 blue in the same quantities of alcohol and water as 

 are required to prepare the Bismarck brown stain ; 



