92 MICROSCOPIC EXAMINATION OF BACTERIA. 



clear. Stain for five or ten minutes; wash in water, dry in 

 the air, and mount in Canada balsam. 



STAINING BACTERIA IN TISSUE : The tissue is removed, 

 fixed, and hardened according to the rules laid down in text- 

 books on histology, and embedded in celloidin or paraffin. 

 The cut sections are stained with Loeffler's alkaline methy- 

 lene-blue, and then differentiated with a 1 per cent, solution 

 of hydrochloric acid for a few seconds, dehydrated in absolute 

 alcohol, cleared in xylol, and mounted in balsam. 



Pfeiifer stains the sections for one-half hour in dilute 

 carbol-fuchsin, and then transfers them to absolute alcohol 

 slightly acidulated with acetic acid. As soon as the section 

 takes on a reddish-violet color it is transferred to xylol, 

 cleared, and mounted in balsam. 



A very simple method is to stain with the ordinary aqueous 

 staining solutions for from five to eight minutes, and then 

 decolorize in a 1 per cent, acetic acid solution for a few 

 seconds. This removes the stain from the tissues, but leaves 

 the color in the bacteria. Any contrast-stain may be used, 

 after which the specimen is dehydrated in absolute alcohol, 

 cleared in xylol, and mounted. Gram's stain is used also 

 for staining bacteria in tissue. The specimen is stained first 

 in Ehrlich's anilin-water gentian-violet for from five to thirty 

 minutes, washed in water, immersed in Gram's solution for a 

 few minutes, washed in 95 per cent, alcohol until thoroughly 

 decolorized, dehydrated in absolute alcohol, cleared in xylol, 

 and mounted. 



