THE BACILLUS OF TYPHOID FEVER. 



437 



0.5 to 0.8 [j. broad, with rounded ends; may also grow out into long 

 threads, especially upon the surface of cooked potato. The dimen- 

 sions of the rods differ considerably in different media. Spherical or 

 oval refractive granules are often seen at the extremities of the rods, 

 especially in potato cultures kept in the incubating oven ; these are 

 not reproductive spores, as was at first supposed. The bacilli have 

 numerous flagella arranged around the periphery of the cells usually 

 from five to twenty, but many short rods have but a single 



FIG. 106. FIG. 107. 



FIG. 106. Bacillus typhi abdominalis, from single gelatin colony. X 1,000. From a photo- 

 micrograph. (Frankel and Pfeiffer. > 



FIG. 107. Bacillus typhi abdominalis, from single gelafn colony. X 1,000. From a photo- 

 micrograph. (Sternberg.) 



terminal flagellum. These flagella are spiral in form, about 0. 1 /* 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). 



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- 



