Bacillary Dysentery 649 



entery bacillus, and that the validity of much that is accepted at 

 present may have to be amended. This seems to be particularly 

 true with regard to the matter of fermentation, the details of which 

 are displayed in the table taken from Muir and Ritchie's " Manual 

 of Bacteriology" (p. 650). 



Morphology. — ^The organism is a short rod with rounded ends, 

 generally similar to the typhoid bacilli. It usually occurs singly, 

 but may occur in pairs. It is frequently subject to involutional 

 changes. It is doubtfully motile and is probably without flagella. 



Staining. — 'When stained with methylene-blue the ends color 

 more deeply than the middle; and organisms from old cultures 

 show numerous involution forms and irregularities. It stains 

 with ordinary solutions, but not by Gram's method. It has no 

 spores. 



Cultivation. — ^The organism grows well in slightly alkaline media 

 under aerobic conditions. 



Colonies. — ^The colonies upon gelatin plates are small and dew- 

 drop-Uke in appearance. Upon microscopic examination they are 

 seen to be regular and of spheric form. By transmitted light they 

 appear granular and of a yellowish color. They do not spread out 

 in a thin pellicle like those of the colon bacillus, and there are no 

 essential differences between superficial and deep colonies. 



Gelatin Punctures. — ^The growth in the puncture culture consists 

 of crowded, rounded colonies along the puncture. A grayish-white 

 growth forms upon the surface. There is no liquefaction of the 

 medium. 



Agar-agar. — ^Upon the surface of agar-agar, cultures kept in 

 the incubating oven show large solitary colonies at the end of 

 twenty-four hours. They are bluish-white in color and rounded 

 in form. The surface appears moist. In the course of forty- 

 eight hours a transparent border is observed about each colony, and 

 the bacilh of which it is composed cease to stain evenly, presenting 

 involution forms. 



Glycerin agar-agar seems less well adapted to their growth than 

 plain agar-agar. Blood-serum is not a suitable medium. 



Litmus Milk.— Milk is not coagulated. As the growth progresses 

 there is sUght primary acidity, which later gives place to an in- 

 creasing alkaUnity. 



Potato. — Upon boiled potato the young growth resembles that 

 of the typhoid bacillus, but after twenty-four hours it becomes 

 yellowish brown, and at the end of a week forms a thick, brownish- 

 pink pellicle. 



Bouillon. — In bouiUon the bacillus grows well, clouding the 

 liquid. No pellicle forms on the surface. 



Metabolic Products. — The organism does not form indol, does 

 not ferment dextrose, lactose, saccharose, or other carbohydrates. 



