2 SO BACTERIOLOGY. 



Alcohol . . . . . 70 

 Nitric acid ... .30 



which must be filtered before use. The sections are 

 washed in water (or weakly acidified 50 per cent, alcohol), 

 dried and mounted in the usual way. 



Pfuhl-Petris method. The colouring solution consists of 

 10 ccm. of a saturated alcoholic solution of fuchsine added 

 to 100 ccm. of water. Float the cover-glasses for two 

 minutes in the solution heated till steam rises. Wash for 

 one minute in glacial acetic acid, rinse in water, and after- 

 stain in an alcoholic or watery solution of malachite green 

 for a half or one minute. Rinse again in water. Dry, and 

 examine in glycerine, or preserve in Canada balsam. 



Senkewitsctt s method. Stain cover-glass-preparations in 

 concentrated fuchsine solution. When strongly coloured, 

 wash out the stain for one to two minutes in alcohol, to 

 which one drop of nitric acid has been added for every 

 10 ccm. Rinse in water, dry, and mount in Canada balsam. 



Kaatzers method. Place the cover-glass-preparations 

 for twenty-four hours in a solution of over-saturated alco- 

 holic gentian-violet, or, if warmed to 80 C., for three 

 minutes. Decolorise in a solution consisting of 



Alcohol go per cent. . '..'. 100 ccm. 

 Water . . . ... 20 ccm. 



Strong hydrochloric acid ... 20 drops. 



Rinse in 90 per cent, alcohol, and after-stain with concen- 

 trated watery solution of vesuvin for two minutes ; wash 

 again in distilled water, dry, and mount in Canada balsam. 

 EhrlicHs method and eosin. The author has found that 

 after sections have been stained with methyl-violet and 

 bismarck-brown by Ehrlich's method, as described by Koch 

 (p. 163), they may with advantage be immersed in a weak 

 alcoholic solution of eosin, then rinsed in clean absolute 

 alcohol, clarified with clove-oil, and mounted in Canada 



