32 HISTOEICAL NOTES ON BEE DISEASES. 



liquefies, and iii tliese 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 fii'st 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 3^ pL. On agar the rods are 

 always somewhat pointed at the ends and varying in size. The 

 average length is about 3^ fi and the breadth about f /x. At the 

 beginning of spore formation the rods begm 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 withm 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 slight but not tena- 

 cious pellicle. The odor is similar to that described under gelatin. 

 Tliis 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 wliitish 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.— Ai 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 3'^ellowish color and gives off the odor present in 

 gelatin-tube cultures. The coagulation is not firm, but like tremu- 

 lous jelly and may remain so for a considerable time before the sep- 



