172 HOG CHOLERA 



Morphology. — A rod-shaped organism varying in size according to 

 the medium in which it has developed. From agar cultures it is from 

 1.2 to 1.8/-/ long and from .5 to .8// broad. The ends are rounded. 

 Spores have not been observed. It is actively motile and a variable 

 number but usually from 3 to 5 flagella have been demonstrated. The 

 length of the flagella also varies. The average seems to be about 7// — 

 although filaments 55 microns with an average length of 35 to 40// are 

 reported by Ferrier. It stains readily with the aniline dyes. Prepara- 

 tions made from cultures usually stain uniformly ; while in the prepara- 

 tions made from the tissue of inoculated animals there is frequently 

 exhibited a light center with a deeply stained peripherj'. 



Cultural characters and biochemic properties. — This bacillus is 

 grown readily on all of the ordinary media used in bacteriological work 

 at a temperature of 30 to 38° C. It is aerobic and facultative anaerobic. 



Agar. — On the surface of inclined agar after 24 hours at a tempera- 

 ture of 37° C. a grayish, glistening nonviscid growth appears. When 

 isolated the colonies are nearly round, convex, 0.5 to 2.0 mm. in 

 diameter. The edges are sharply defined and even. In stab cultures a 

 grayish growth develops along the needle track with a more vigorous 

 growth on the surface about the needle puncture. The growth reaches 

 its maximum in about 48 hours. 



Gelatin. — In this medium the growth is moderately feeble, the 

 colonies appearing as grayish dots. When magnified they are finely 

 granular and of a yellowish tint. The quantity and form of growth 

 depends considerably upon the reaction of the gelatin. If decidedlj' 

 alkaline there is often a tendency for the growth to spread. There is no 

 softening or liquefaction of the medium. 



Potato. — The growth on potato takes the form of a verj- thin, glisten- 

 ing layer. It is usually of a faintly yellowish color but this is subject 

 to variation on different potatoes. If the reaction is strongly acid no 

 growth appears. 



Bouillon. — In alkaline bouillon it imparts in 24 hours a uniformly 

 ■cloudy appearance to the liquid. Ordinarily there is no membrane on 

 the surface. After some days' standing the growth begins to settle, 

 forming a grayish, friable sediment. If the bouillon contains muscle 

 sugar the reaction will be changed to acid, in from 24 to 48 hours, due 

 to the fermentation of the sugar. Later, however, the liquid will 

 become strongly alkaline, unless there was too much muscle sugar pres- 

 ent. In acid bouillon the growth is less vigorous. It grows better in a 

 bouillon containing peptone than in a simple beef broth. 



Milk. — When the milk is acid in the beginning it gradually becomes 

 alkaline. There is no precipitation or coagulation of the casein. After 

 standing for from two to three weeks in an incubator a gradually 

 developing opalesence of the milk can be observed. Later it becomes 

 clear, then light brownish in color. If allowed to stand longer in the 

 incubator the volume of the culture shrinks by evaporation and the 



