THE bacillus of typhoid fever (Fig. 105) was discovered
by Eberth and Koch in 1880, and was first secured in
FIG. 105.—Bacillus typhi, from a twenty-four-hours-old agar-agar culture;
x 650 (Heim).
pure culture from the spleen and affected lymphatic
glands by Gaffky four years later.
The organism is a small, short bacillus about 1-3 ^
(2-4^ Chantemesse, Widal) in length and 0.5-0.8^ broad
(Sternberg). The ends are rounded, and it is rather ex-
ceptional for the bacilli to be united in chains, though
this arrangement is common in potato cultures. The
size and morphology vary distinctly with the nature of
the culture-medium and the age of the culture. Thoinot
and Masselin in describing these morphological peculi-
arities mention that when grown in bouillon it is a very
slender bacillus; in milk it is a large bacillus; upon
agar-agar and potato it is very thick and short; and in
old gelatin cultures it forms very long filaments.