470 



PATHOGENIC MICROORGANISMS 



produces spores at temperatures above 20 C., which are oval, irregularly 



placed either in the center or slightly nearer one or the other end, and 



cause a bulging of the bacillary body. 



It is readily stained by any of the usual' 1 anilin dyes. Stained by 



Gram's method it is decolorized. 



Cultivation. Bacillus oedematis maligni is strictly anaerobic. 

 Under anaerobic conditions it develops readily upon 

 any of the usual artificial media. The bacillus is not 

 very sensitive to the reaction of media and grows 

 more luxuriantly in all media to which glucose has 

 been added. In all media it forms, by the cleavage of 

 proteids, putridly offensive gases. 



In gelatin at room temperature, colonies develop in 

 about three days as small grayish spherical growths, 

 which microscopically show an arrangement in radial 

 filaments. The gelatin is fluidified. 



In gelatin stab cultures growth begins as a white 

 column extending to within a centimeter of the top 

 of the medium. Soon irregularly radiating processes 

 develop laterally and gas bubbles appear, breaking up 

 the medium. 



Stab cultures in agar show growth within twenty- 

 four to thirty-six hours at 37.5 C., appearing at first 

 as a white line, but soon showing a cloud-like lateral 

 extension along the entire line of the stab. If sugar 

 is present bubbles appear throughout the medium. 



In broth there is general clouding and a granular 

 sediment; no pellicle is formed. Milk is slowly coag- 

 ulated. On blood serum growth is very luxuriant. 

 On potato, a medium used in the earliest studies of 

 the bacillus by Gaffky, the bacillus grow r s readily. 



Isolation may be accomplished by any of the 

 ordinary anaerobic plating methods. The bacillus 

 can usually be obtained for subsequent isolation by 



injection of a susceptible animal with soil, especially that of gardens or 



manured fields. 



Pathogenicity. The bacillus is pathogenic for mice, guinea-pigs, 



rabbits, horses, dogs, sheep, pigs, some birds, and man. Cattle were 



formerly regarded as immune, an opinion which has since been found to 



be erroneous. 



FIG. 102. BA- 

 CILLUS OF MA- 

 LIGNANT EDEMA. 

 Culture in glu- 

 cose agar. 



