4 PRACTICAL BACTERIOLOGY. 



(c) Fuchsin. Several staining solutions are used of 

 this dye, of these Ziehl's carbol-fuchsin is most useful. 

 This stain is made by taking, 



Saturated alcoholic solution of fuchsin 



crystals 11 cc. 



5% carbolic acid solution . . 89 cc. 



Fuchsin can also be used as anilin water fuchsin, 

 or as diluted fuchsin. These are made of the same 

 strength as the like preparations of gentian violet. 



All stains must be filtered before use. 



Cover glasses should be kept in alcohol and handled 

 with forceps. When they are required for use, rub dry 

 with a clean cloth. 



1. (a) Take a clean cover glass and sterilize it by 

 passing it quickly through the gas (or spirit lamp) 

 flame. Then with a platinum loop (using all the pre- 

 cautions of the first lesson), remove a drop of the lique- 

 fying gelatine culture of Staphylococcus pyogenes 

 aureus, and smear this over the cover glass. 



(b) Allow the film to dry in the air, or dry it by 

 holding it high over the flame. Fix the film by passing 

 it quickly three times through the flame. 



(c) Clear away the gelatine by placing the cover 

 glass in 10% acetic acid for five minutes. 



(d) Remove from the acid, rinse through water and 

 then dry. 



(e) Float the cover glass, film surface down, in anilin 

 water gentian violet, or in diluted gentian violet, for 



