10 BXILLETIN 810, V. S. DEPAKTMENT OF AGEICXJLTTJEE. 



BACILLBS PLUTON 



An artificial medium for the cultivation of Bacillm piston has not 

 yet been devised. To accomplish this may or may not be a particu- 

 larly difficult task. The media ordinarily used m the laboratory are 

 not suitable. Bee-larv^ agar, brood-filtrate media, egg-yolk-sus- 

 pension agar (19), and combinations of these have not thus tar 

 proved sufficient for the purpose. The species is an unusual one. 

 The generic classification has not been determined definitely and this 

 may not be possible until the proper condition for the artificial culti- 

 vation of the species has been supplied. 



The morphology of Bacillus pluton is somewhat variable, in very 



early infection its form is that of a short rod in pairs or in chains, or 



possibly of a coccus with the individuals similarly arranged (fag. 1; 



PI VII B) The length is then equal to or somewhat greater than 



' the breadth. In slightly later 



stages of infection the predomi- 

 nating form is that of a lancet- 

 shaped coccus (fig. 1; PI. VII, 

 A), and in late stages this form 

 is present almost exclusively. 

 The lancet form occurs singly, 

 varying greatly in size and hav- 

 ing a length which approximates 

 twice the width. The length is 

 more often less than 1 [^ than 

 greater. The organism colors 

 uniformly with the aniline stains, 

 FIG. i.-BaciJius pluton. ^tains with iron hematoxylin, and 



is gram-positive. It does not 

 form spores. This is evidenced by the microscopic appearance and 

 also by the thermal death point of the species. Its resistance to dry- 

 ing, disinfectants, and other environments is discussed later in the 

 present paper. 



Seven rabbits inoculated, six subcutaneously and one intraperi- 

 toneally, with a suspension of larvae dead of European foulbrood 

 proved to be refractory. Only a slight rise of temperature followed 

 the inoculations and the weight was not materially affected. Six 

 guinea pigs inoculated subcutaneously with similar material proved 

 not to be susceptible to infection with the species. Four pigeons 

 inoculated in the pectoral muscles and two white rats inoculated sub- 

 cutaneously also proved refractory. In none of these inoculated ani- 

 mals were there any lesions of particular note produced. 



Growth of Bacillus pluton in the infected larva begins close to the 

 surface of the peritrophic membrane (PI. VII, I) in contact with the 

 food of the larva. As growth continues the bacterial mass extends 

 toward the center of the lumen of the peritrophic sac (PI. VII, K), 



