Pathogenic Bacteria

TYPHOID FEVER. 367

The organisms are actively motile, the motility prob-
ably being caused by the numerous flagella with which
the bacilli are provided. The flagella stain well by
Loffler's method, and, as they are numerous (ten to
twenty) and readily demonstrable, the typhoid bacillus is
the favorite subject for their study. The movements of

FIG. 106.—Bacillus typhi, from an agar-agar culture six hours old, showing the
flagella stained by Loffler's method; x 1000 (Frankel and Pfeiffer).

the short bacilli are oscillating, those of the longer indi-
viduals serpentine.

The organism stains quite well by the ordinary meth-
ods, but loses the color entirely when stained by Gram's
method. Its peculiarity of staining is the readiness with
which the bacillus gives up its color in the presence of
solvents, so that it is particularly difficult to stain it in
tissue.

When sections are to be stained the best method is to
allow the tissue to remain in Loffler's alkaline methylene
blue for from fifteen minutes to twenty-four hours, then
wash in water, dehydrate rapidly in alcohol, clear up in
xylol, and mount in Canada balsam. Ziehl's method
also gives good results. The sections are stained for fif-
teen minutes in a solution of distilled water 100, fuch-