EXAMINATION OF BACTERIA WITH THE MICROSCOPE. 45 



cover-glass with the platinum wire, which is sterilized in the 

 flame before and after using. The selection of the little 

 white particles will be facilitated if the sputum be poured 

 into a clean glass dish, which may be placed on a black sur- 

 face. A form of porcelain dish is furnished by dealers, the 

 bottom of which is black, and which is convenient, for these 

 manipulations. The smears must be made thin, or the sub- 

 sequent decolorization, after staining, will not be uniform. 

 It is hardly necessary to observe that the operator must be 

 scrupulously careful not to contaminate the material under 

 examination with any kind of extraneous matter. The 

 cover-glasses and slides which are used should be new, and 

 should have been cleaned with bichromate of potassium and 

 sulphuric acid (see page 36). 



When the work is completed, the bottle containing the 

 sputum should be sterilized by steam or boiling. 



Many different methods for staining the tubercle bacillus 

 have been proposed. In most of those now in use the fol- 

 lowing solution is employed 



Fuchsin i gram. 



Carbolic acid, pure 5 c.c. 



Alcohol 10 c.c. 



Distilled water 100 c.c. 



The method given below is the one recommended. 

 Method for staining the tubercle bacillus: 



(a) The cover-glass preparation is made, dried, and fixed 

 by passing through the flame three times. 



(b) The cover-glass, held in forceps or in a watch- 

 crystal is covered with steaming carbol-fuchsin for five 

 minutes. 



(c) Wash in water. 



(d) Wash in alcohol containing 3 per cent, of hydro- 

 chloric acid one minute, or longer if necessary to remove 

 the red color. 



