LESSON III 



Staining of Bacteria (continued) Loffler's Methylene-blue Examina- 

 tion of Moulds Hanging Drop Cultures. 



Loffler's Methylene-blue 



PREPARE and stain cover-glass films of the various cultures 

 made during the previous lesson. 



(1) Bacillus prodigiosus : agar-agar culture. 



(a) On a clean cover-glass place a small drop of sterile 

 distilled water. With a sterilised platinum needle remove 

 a trace of the culture, and, mixing it with the drop of 

 water, spread it uniformly over the cover-glass. 



(b) Allow the film to dry in the air, and then pass the 

 cover-glass three times through the flame and proceed as 

 before (vide p. 9), staining the film with methylene-blue. 



If necessary, clear the film with acetic acid (20 per 

 cent). 



Instead of the ordinary aqueous solution of methylene- 

 blue Loffler's methylene-blue may be used with advantage. 

 This is one of the best and most certain of staining 

 solutions, and gives almost always good results. It is 

 prepared in the following manner : 



