CHAPTER III. 

 STAINING METHODS. 



L\ order to study a bacterial or blood specimen the first essential is 

 a properly prepared film the matter of staining is of less importance. 

 The slide or cover glass, after cleaning with soap and water or by 

 special solutions, should be polished with a piece of old linen. If a 

 glass surface is free of grease a loopful of water will smear out evenly 

 and over the entire surface. The only quick practical way to make 

 the slide or cover -glass grease free is to burn the surface for a moment 

 in a Bunsen or alcohol flame. The cover -glass must not be warped. 

 To make a preparation, apply a small loopful-of distilled water on the 

 slide or cover glass and, touching a colony with a platinum needle, 

 stir the transferred culture into the loopful (not drop) of water. The 

 mistake is almost invariably made of taking up too much bacterial 

 growth. Fluid cultures do not need dilution. Smearing the mixture 

 over a large part of the cover-glass or over an equal area of a slide, it is 

 allowed to dry. If very little water is used, the preparation dries 

 readily. Otherwise it can be dried in the fingers high over a flame. 

 As soon as dry, the cover glass should be passed three times through 

 the flame, film side up, to fix the preparation. Slides may be fixed by 

 passing them five times through the flame, but the method by burning 

 aVohol recommended for fixing blood-films gives more satisfactory 

 bacterial fixation. For routine work the stain recommended is a 

 dilute carbol fuchsin. Drop about five to ten drops of water on the 

 cover-glass, then add one drop of carbol fuchsin. Allow the dilute 

 stain to act from one to two minutes, then wash in water, dry between 

 small squares of filter-paper (4x4 in.), and mount in balsam or the 

 oil used for the 1/12 in. immersion objective. Some prefer to mount 

 directly in water without preliminary drying. It is good practice to 

 make a rule to always keep the smeared side of the preparation up 

 never allowing it to be reversed. By this simple rule, preparations 



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