38 ESSENTIALS OF BACTERIOLOGY. 



CHAPTER VI. 



SPECIAL METHODS OF STAINING AND MODIFICATIONS. 



Gram's Method of Double Staining. (For cover-glass speci- 

 mens.) I. A hot solution of anil, water gentian violet 2 to 1U 

 minutes. 



II. Directly without washing, into Gram's solution of iod. 

 potass, iod. 1 to 3 min. (the cover-glass looks black). 



III. Wash in alcohol 60 per cent, until only a light brown 

 shade remains (as if the glass were smeared with dried blood). 



IV. Rinse off alcohol with water. 



V. Contrast color with either eosin, picro-carmine, or bismark- 

 brown. The bacteria will appear deep blue, all else red or brown 

 on a very faint brown background. 



The following bacteria do not retain their color with Gram's 

 method are therefore not available for the stain : 

 Bacillus of typhoid. 

 Spirillum of cholera. 

 Bacillus of chicken cholera. 



" of hemorrhagic septicaemia. 

 " of malignant oedema. 

 " of pneumonia (Friedlander). 

 " of glanders. 

 Diplococcus of gonorrhoea. 

 Spirillum of relapsing fever. 

 Gram's Method for Tissues (modified by Giinther). 



I. Stain in anil, water gent, violet' . . 1 minute. 



II. Dry between filter paper. 



III. Iod. potass, iod. sol. .... 2 minutes. 



IV. Alcohol minute. 



V. 3 perct. sol. hydrochloric acid in alcohol 10 seconds. 



VI. Alcohol, ol. of cloves, and Canada balsam. 



To Stain Spores. Since spores have a very firm capsule, 

 which tends to keep out all external agents, a very intensive 

 stain is required to penetrate them, but once this object attained 

 it is equally as difficult to decolorize them. 



