EUROPEAN rOULBROOD. 39 



PJ.ATE VI 



A view of the experiiuoutal aitiary of 54 colonics in which (h(! inoculation ex- 

 periments made (Uirinj? tlie summer of 1915 were conducted. 



Plate VII 



Photomicrograplis illusli-atin^^ llie iiioiv commonly encountered bacteria 

 in European foulhrood. 



A. — liacilius pluton: A smear from the stomacli of a larva sick witli Euro- 

 pean foulhrood. Note the paired forms and sliort 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 lat<'r 

 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 curydice: 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. 



P. — 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 orphcus: Stained preparation made from a pure culture only 

 a few hours old. Grown on the surface of agar. X 1000. 



H. — Bacillus orplieus: 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 j^oung larva showing early infection in European 

 foulhrood. 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 foulhrood, showing a later stage 

 of infection than that present in I. 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. 



K. — Transverse section of larva about the time of its death from European 

 foulhrood 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 larvje thins out as the disease advances. 



Plate VIII 

 The stomach contents of larvae sick of European foulhrood 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 tl>e tension pi'oduced 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 foulhrood 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. 



