THE BACILLUS OP TYPHOID FEVER. 



347 



terminal flagellum. These flagella are spiral in form, about 0. 1 >u in 

 thickness, and from three to five times as long as the rods (Babes). 



In stained preparations unstained " vacuoles" may often be seen 

 at the margins of the rods, either along the sides or at the ends ; 

 these appear to be due to a retraction of the protoplasm from the cell 

 membrane. 



The typhoid bacillus stains with the aniline colors, but more 

 slowly than many other bacteria, and easily parts with its color when 

 treated with decolorizing agents e.g., iodine solution as employed in 

 Gram's method. Loffler's solution of methylene blue is an excellent 

 staining agent for this bacillus, but permanent preparations fade out 

 after a time ; f uchsin, gentian violet, or Bismarck brown, in aqueous 

 solution, may also be used. The flagella may be demonstrated by 

 Loffler's method of staining (p. 32). 



Fie. 110. Bacillus typhi abdominal! s, stained by Loffler's method, showing flagella. x 1,000. 

 From a photomicrograph by Frankel and Pfeiffer. 



To stain the bacillus in sections of the spleen, etc. , it is best to 

 leave these in Loffler's methylene blue solution or in the carbol- 

 fuchsin solution of Ziehl for twelve hours or more ; or the aniline- 

 fuchsin solution may be used. The sections should be washed in 

 distilled water only, when Ziehl's solution is used, or with a very di- 

 lute solution of acetic acid when Ehrlich's tubercle stain is employed 

 (Baumgarten). 



Biological Characters. The typhoid bacillus is a motile, aero- 

 bic, non-liquefying bacillus, which grows readily in a variety of 

 culture media at the " room temperature." Although it grows most 

 abundantly in the presence of free oxygen, it may also develop in its 

 absence, and is consequently a facultative anaerobic. 



