98 STUDY OF BACTERIA 



plasm, forming, as it were, a double salt between the two. Cer- 

 tain substances, alkalies, carbolic acid, iron and copper sulphate, 

 tannic acid, alum, and aniline oil, are added to a solution of aniline 

 dyes, and they act as mordants, or fixatives, making the dye bite 

 into the protoplasm of the bacterial cells. Spores, capsules, and 

 flagella, are hard to stain, and special heavily mordanted stains are 

 used to demonstrate them. Chemical reaction occurring in the 

 cell protoplasm is of great value in differentiating bacteria. The 

 presence of granules in bacterial cells is often only shown by 

 the use of special stains, which deeply color them. Bacteria of the 

 tubercle group are called "acid-fast," because, after being stained, 

 it is difficult to decolorize them with acid solutions. These bac- 

 teria are hard to stain and resist decolorizing agents after they 

 are stained. 



1 . Loffler's alkaline methylene blue solution consists of 



Saturated alcoholic solution of methylene blue 30 c.c. 



Ho, ooo solution caustic soda solution in water 100 c.c. 



Mix. 



This is the most useful of all the staining mixtures employed. 



2. ZeihFs solution carbol-fuchsin consists of 



Fuchsin i gram. 



Carbolic acid crystals 5 grams. 



Dissolved in 100 c.c. of water, to which is added 10 c.c. of absolute alcohol. 



This can also be made by taking a 5 percent solution of carbolic 

 acid in water and adding sufficient saturated solution of fuchsin in 

 water until a bronze scum persists upon the top. This is used for 

 staining tubercle bacilli in sputum and sections. It must be 

 heated when used for rapid staining. Tubercle bacilli can be 

 stained in cold solution, if immersed over night in it. 



3. Fuchsin solution. 



Saturated alcoholic solution of basic fuchsin i c.c. 



Water. . . . 100 c.c. 



