538 BACTERIOLOGY. 



is employed in decoloration and the length of time that 

 these are allowed to act on the stained section likewise 

 affect the result. In the event of failure the student, there- 

 fore, should ascertain by systematic trial which of these 

 factors is the one at fault. Success in staining sections 

 requires an intelligent perseverance in, and a study of the 

 method employed. 



As a rule, a few sections should be transferred to some 

 water in an Esmarch or Petri dish. Owing to the diffusion 

 currents the sections spread out perfectly. The thin sec- 

 tions can then be transferred by means of a mounted needle, 

 at times assisted by a spatula, to the filtered, staining fluid. 

 The latter contains either fuchsin, gentian violet or methyl- 

 ene blue. 



( The fuchsin can be used in dilute aqueous solution 

 (p. 147), such as is employed in the simple staining of cover- 

 glasses. Carbolic fuchsin (p. 292) is used for the simple and 

 double staining of bacteria. 



Gentian violet is employed in dilute aqueous solution, 

 or as anilin-water gentian violet (p. 288). This dye stains 

 rapidly and deeply and it should not, therefore, be allowed 

 to act as long as the other dyes. 



Methylene blue is a slow, weak stain and should be 

 allowed more time to act than either of the preceding. It 

 may be used in dilute aqueous solution or as Loffler's alka- 

 line methylene blue solution (p. 332). Kiihne's carbolic 

 methylene blue, made by adding 1.5 g. of methylene blue 

 and 10 g. of alcohol to 100 c.c. of 5 per cent, carbolic acid 

 and heating till complete solution takes place, is very 

 useful. 



ANTHRAX BACILLUS. 



Simple stain. The section is transferred from water to 

 the dilute anilin dye, and is allowed to remain there for 

 from 5 to 15 minutes. It is then washed for 2 or 3 minutes 



