ao HISTORICAL NOTES ON BEE DISEASES. 
liquefies, and in these liquid channels the bacilli swim to and fro. 
Later some of these channels are apparently deserted of bacilli, so 
that the circles may look as though they were detached from the main 
track. Under low powers, however, the connection between them 
can be traced. 
If the gelatin is inoculated before pouring the plate, the growth 
which takes place is also very characteristic. At first the colonies 
are small and oval or round. Under a low power of the microscope 
the colony does not appear homogeneous, but lines indicating the 
bacilli are seen. The colony soon becomes pear-shaped, and proc- 
esses grow out from the sharp end of the pear into the gelatin. 
Morphology: Rods.—In the larval juices they are rounded or 
slightly tapering at the ends, and often have a clear space near one 
end. Their average length is about 34 4. On agar the rods are 
always somewhat pointed at the ends and varying in size. The 
average length is about 34 4 and the breadth about 3 ». At the 
beginning of spore formation the rods begin to swell and become 
spindle shaped. This increase in diameter is generally near the mid- 
dle, but sometimes it is seen near one end. The capsule of the spore 
is apparently formed within the rod, and is not merely the outer por- 
tion of it. Spores.——The spores are oval, averaging nearly 2 » in 
length and nearly 1 » in breadth. Spores from agar cultures are 
generally arranged side by side in long rows. 
Motility —The bacilli swim with a free oscillating movement. 
Bouillon —Growth takes place readily, causing a cloudiness of the 
medium and the formation after a few days of a shght but not tena- 
cious pellicle. The odor is similar to that described under gelatin. 
This character is more marked when considerable peptone is present. 
Probably there is no change in the chemical reaction. 
Agar—The growth is not nearly so characteristic as in gelatin. 
It takes place most rapidly on the surface, forming a whitish layer. 
Here the bacilli arrange themselves side by side and, forming spores 
in this position, there are after a few days, as a consequence, long 
rows of spores lying side by side. 
Blood serum.—Growth takes place slowly forming long filaments 
and comparatively few spores. 
Potato—At the incubator temperature the growth takes place 
slowly, forming a dryish yellow layer on the surface. It is very slow 
at lower temperatures. 
Milk —Growth takes place readily and coagulation occurs. The 
medium assumes a yellowish color and gives off the odor present in 
gelatin-tube cultures. The coagulation is not firm, but lke tremu- 
lous jelly and may remain so for a considerable time before the sep- 
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