STAINING SOLUTIONS 115 



A very useful, though somewhat feeble, staining solution. 

 Cultures should be quite fresh, or the organisms do not stain 

 well. When the organisms are mixed with extraneous material, 

 as in smears, or there is much debris, this is one of the best stain- 

 ing solutions to employ. Methylene blue preparations are, 

 however, not very permanent, and in hot countries rapidly fade. 

 Thionine blue is then preferable. (See below.) 



Film specimens are stained for three to ten minutes, and 

 sections half to twenty-four hours. 



(2) Carbol-methylene blue (Kiihne) : 



Methylene blue . . . . . . 1-5 grm. 



Absolute alcohol ...... 10 c.c. 



Five per cent, aqueous solution of carbolic acid 100 c.c. 

 A more intense staining solution than the former, and very 

 useful for sections, which are stained for from half to six hours. 



(3) Carbol-gentian violet : 



Saturated alcoholic solution of gentian violet . 10 c.c. 

 Five per cent, aqueous solution of carbolic acid 100 c.c. 

 A more intense staining reagent than methylene blue. May be 

 used for Gram's method (p. 119). 



(4) Carbol-fuchsin (Ziehl-Neelsen solution) : 



Fuchsin 1 part 



Absolute alcohol . . . . . .10 parts 



Five per cent, aqueous solution of carbolic acid 100 parts 

 The f uchsin is dissolved in the absolute alcohol and then mixed 

 with the carbolic acid solution. Filter before use. 



An intense staining solution. For films it is best diluted with 

 five to ten parts of water ; stain for two to five minutes. 



(5) Carbol-thionine blue (Nicolle) : 



Saturated solution of thionine blue in alcohol 



(90 per cent.) . . . . . .10 c.c. 



One per cent, aqueous solution of carbolic acid 100 c.c. 

 Sections can be stained in from a few minutes to half an hour. 

 May be used for Gram's method (p. 119). A substitute for 

 methylene blue for all purposes, and is more permanent than the 

 latter. 



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