BACTERIA. 161 



glass, pour a little staining solution into a watch-glass, and place 

 the cover on it, with the dried material downwards^ leave for from 

 5—60 minutes. The time can only be learnt by practice, as the 

 materials differ. When thoroughly stained, wash the cover-glass 

 in methylated or rectified spirits until all the superfluous colour is 

 removed, taking care that it is not washed too much, or the 

 Bacteria film washed off". Then dry the cover-glass by holding it 

 on its edge on blotting-paper, allow to dry. Then mount in 

 Canada Balsam. 



To Stain Sections of Tissue containing Bacteria. — Place them 

 in the stains given below and leave for some hours. When deeply 

 stained, wash in water to remove excess of stain, then lay them out 

 flat in spirit and leave till no more colour comes away. Transfer 

 to absolute alcohol which fixes the colour, then to clove oil, and 

 mount in Canada Balsam. 



The best stains are Gentian Violet, Spiller's Purple, and 

 Methyl Blue, the great difficulty being to obtain good samples 

 of the dye, as the manufacturers change the numbers often, and 

 the anilins differ greatly. 



Gentian Violet, 2%. — Take 2 grms. of the powder, rub it up 

 in a mortar with 10 c.c. alcohol (sp. gr., o'83o), some prefer that 

 in which 2 c.c. of anilin oil has been dissolved. Then add 

 gradually 90 c.c. of distilled water while stirring. 



Spiller's Purple. — Make as above, using the same strength. 



Methyl Blue.— A 2% solution in distilled water and a little 

 alcohol added whilst triturating the powder, previous to the water 

 being added. (A litde Liq. Potassae, i c.c, may be added in 

 preference to alcohol, if desired.) 



Grain's method, with a saturated alcoholic solution of gentian 

 violet and anilin water and iodide of potassium, is good. 



For Bacilli in Sputum and Tissue. — The methods are very 

 numerous, but I prefer Gibbes' Double-Stain or his Magenta and 

 Nitric Acid Methods, as they are always to be relied on if the dyes 

 are pure and take very little time. I have seen and prepared 

 specimens of sputa in five minutes for diagnostic purposes. The 

 Bacilli do not fade. 



