THE BACILLUS OF TYPHOID FEVER. 437 
0.5 to 0.8 » 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 
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Fie. 106, Fia. 107. 
Fic. 106.—Bacillus typhi abdominalis, from single gelatin colony. X 1,000. From a photo- 
micrograph. (Frinkel and Pfeiffer.) 
FiG. 107.—Bacillus typhi abdominalis, from single gelat‘n 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. Léffler’s solution of methylene blue is an excellent 
staining agent for this bacillus, but permanent preparations fade out 
after a time ; fuchsin, gentian violet, or Bismarck brown, in aqueous 
solution, may also be used. The flagella may be demonstrated by 
Léffler’s method of staining (p. 32). 
To stain the bacillus in sections of the spleen, etc., itis best to 
leave these in Léffler’s methylene blue solution or in the carbol- 
fuchsin solution of Ziehl for twelve hours or more; or the aniline- 
