148 
Journal of Agricultural Research 
Vol. XXI. No. 3 
THE ORGANISM 
DESCRIPTION 
The causal organism is a short rod with rounded ends, single, in pairs 
or chains, 1 to 2 u long by 0.5 to 0.7 m broad, when stained from 24- 
hour agar cultures. It is motile by means of one to three bipolar flagella 
(PI. 38, B). It does not form spores, is Gram-negative, is not acid-fast 
and stains readily with the ordinary anilin stains. Capsules were stained 
from 10-day agar cultures with Ribbert’s stain. Rods with swollen ends 
occur in old milk cultures. 
CULTURAL CHARACTERS 1 
Agar plates. —On +15 (Fuller’s scale) peptone-beef agar at 20° to 25 0 
C., colonies appear on the second day. By the fourth day the surface 
colonies are 2 mm. in diameter, thin, white, round with entire margin, wet 
shining, finely granular, semitransparent, with internal concentric mark¬ 
ings by oblique light, especially in the thinner margins. As colonies 
enlarge (5 to 8 mm.) they are white, slightly convex, and may be either 
round or irregularly scalloped (PI. 37, C). The scallops are formed by 
wedges of more transparent growth in which distinct radiating lines are 
seen by direct transmitted light (PI. 38, D). By oblique transmitted light 
the wedges show both radiating lines and also internal concentric markings 
(PI. 38, E). In consistency they are viscid, becoming more so with age. 
Buried colonies are lenticular, becoming round to irregular. 
Agar stabs. —In agar stabs the surface growth is flat, wet shining, 
moderate, at first round, later with an undulate margin, then covering 
the entire surface. Stab growth is moderate, granular, tapering down¬ 
ward, ending at one-half the depth of the agar. In old cultures crystals 
form from the surface downward in ragged spears 1 to 2 cm. long. There 
is no discoloration of the agar. 
Agar streaks.— Two-day-old streaks from bouillon are filiform, 2 
mm. wide, tapering upward, white, wet shining, with thin margins and 
granular center. Later (6 days old) growth is 4 to 5 mm. wide with 
finely scalloped edges and radiating lines by transmitted light, running 
from the granular center into the translucent margins. The V is half 
filled with white precipitate. The growth is very viscid. 
Gelatin plates. —On gelatin plates kept at 15 0 C. colonies appear on 
the fourth day. At 20° they are visible on the second day. Growth is 
very slow and without liquefaction at 15° Colonies are thin, round, 
later becoming flower-like—that is, with a crater-like center and wider 
scalloped margin (PI. 38, C). At 21 0 to 24 0 very slow liquefaction occurs, 
beginning about the tenth day, especially on thickly sown plates. On 
thinly sown plates colonies usually lie in a shallow, dry Saucer. 
1 Kahlbaum’s agar and Difco peptone were used throughout. 
