EUROPEAN FOULBROOD. 39 
PLATE VI 
A view of the experimental apiary of 54 colonies in which the inoculation ex- 
periments made during the summer of 1915 were conducted. 
PLATE VII 
Photomicrographs illustrating the more commonly encountered bacteria 
in European foulbrood. 
A.—Bacillus pluton: A smear from the stomach of a larva sick with Euro- 
pean foulbrood. Note the paired forms and short chains. These forms are 
numerous in a recent infection, suggesting the organism in the process of mul- 
tiplication. The lancet-shaped form is by far the predominant one in all later 
stages of the disease. X 1000. 
B.—Bacillus pluton: A smear from a larva quite recently infected. The 
multiplying paired forms are at this stage present almost exclusively. X 1000. 
C.—Bacterium eurydice: Stained preparation from a pure culture on the 
surface of agar. X 1000. 
D.— Bacillus alvei: Stained preparation showing spores and spore forma- 
tion. X 800. 
E.—Streptococcus apis: Stained preparation from a pure culture. X _ 800. 
F.— Bacillus alvei: The peculiar arrangement of the spores as sometimes 
seen. From a pure culture, the smear having been made by suspending the 
culture on the slide in normal salt solution. X 1000. 
G.— Bacillus orpheus: Stained preparation made from a pure culture only 
a few hours old. Grown on the surface of agar. X 1000. 
H.—Bacillus orpheus: Stained preparation showing spore formation. Note 
the stained portion along one side and about both ends of the spore. The 
stage is soon reached in a culture at incubator temperature. At room tempera- 
ture it remains in this stage for a considerable period. X 800. 
I.—Longisection of a young larva showing early infection in European 
foulbrood. The bacterial growth is seen as a narrow black area just within 
the peritrophic membrane on one side of the food mass. 
J.—Longisection of larva sick of European foulbrood, showing a later stage 
of infection than that present in IJ. The dark area in the food mass shows 
the bacterial growth. Note that the growth mass does not extend beyond 
the peritrophic membrane and that it does not extend uniformly along this 
membrane and throughout the food mass. 
IX.—Transverse section of larva about the time of its death from European 
foulbrood infection. Note the bacterial mass along the peritrophic mem- 
brane and extending from the membrane into the food mass. As seen within 
the living larva this bacterial mass in the sick larva is practically white, but is 
more or less yellowish white when present with larval food material. The 
gelatinous-like envelope outside the peritrophic membrane and inside the stom- 
ach epithelium in healthy larve thins out as the disease advances. 
PLATE VIII 
The stomach contents of larve sick of European foulbrood removed from 
the organ. The anterior end of the larva is shown. Fairly early stage 
of infection (a) showing the white bacterial mass broken into fragments 
as a result of the tension produced in removing the stomach contents from 
the organ. A somewhat later stage (b) in the course of the disease, show- 
ing the bacterial growth contained in the stomach fragmented, also the 
mucous or gelatinous envelope surrounding the petritrophic membrane. The 
stomach contents removed from a European foulbrood larva (¢c) about the 
time of its death. The bacterial growth at this time is surrounded by very 
little other than the peritrophic membrane. When this membrane is ruptured 
the contents flow out as a thin yellowish-white mass. 
