58 ESSENTIALS OF BACTERIOLOGY 



a cover-glass and stained with the ordinary dyes; but in order 

 to eliminate the coloring-matter of the red corpuscles and 

 bring the stained bacteria more prominently into view, 

 Gunther recommends that the blood, after drying and fixing, 

 should be rinsed in a dilute solution of acetic acid (i to 5 per 

 cent.). The hemoglobin is thereby extracted, and the cor- 

 puscles appear then only as faint outlines. 



Instead of " fixing" by heat, Canon employs alcohol for five 

 minutes, especially in staining for influenza bacilli which have 

 been detected in the blood. 



CHAPTER VIII 



SPECIAL METHODS OF STAINING AND MODIFICATIONS 



Gram's Method of Double Staining (For Cover-glass 

 Specimens). I. A hot solution of anilin- water gentian- violet 

 two to ten minutes. 



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

 iodin potassium iodid one to three minutes (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, picrocarmin, or Bis- 

 marck-brown. The bacteria will appear deep blue, all else 

 red or brown on a very faint brown background. 



Gram's Method for Tissues (Modified by Gunther) 

 I. Stain in anilin-water gentian- violet . . i minute 

 II. Dry between filter-paper. 



III. Iodin potassium iodid solution 2 minutes 



IV. Alcohol ]4 minute 



V. 3 per cent, solution hydrochloric acid 



in alcohol 10 seconds 



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



