Bacillary Dysentery 689 



dysentery 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." 



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

 generally similar to the typhoid bacillus. It measures 1.5-3 ^ ^^ 

 length by 0.8 -i m in breadth. It usually occurs singly, but may 

 occur in pairs and rarely in short chains. It forms no spores, is not 

 motile and is 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 or- 

 dinary solutions, but not by Gram's method. 



Isolation. — The bacillus may be obtained in greatest numbers 

 from the flakes of mucus in the dysenteric discharges. To free these 

 from the numerous bacteria of the feces, it has been recommended 

 that they be washed in salt-solution, before being smeared over 

 the surface of plates of such media as are used for the isolation of 

 the typhoid bacillus. As the general cultural difficulties experienced 

 in regard to the typhoid and dysentery bacilli are much the same, 

 the recommendations concerning the former apply equally to the lat- 

 ter. When the colonies supposed to be those of the dysentery bacilli 

 have been isolated and transplanted, the final identification must 

 be made by comparison with the table showing the general require- 

 ments, and by the application of the agglutination test by appropriate 

 serums. 



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

 at temperatures between 10° and 42°C. The most vigorous growth 

 takes place at about 37°C. It is an aerobe and optional anaerobe. 



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

 drop-like 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 Hke 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 inform. 

 The surface appears moist. In the course of forty-eight hours a 

 transparent border is observed about each colony, and the bacilli 

 of 'which it is composed cease to stain evenly, presenting involution 

 iorms. 

 44 



