706 PATHOGENIC MICROORGANISMS 



Bacilli of Group I.: 



"Shiga" .' less than 100 



"Kruse".. . 100 



" New Haven" 100 



Bacilli of Group II.: 



"Y" 400 



"Ferra" 400 



"Seal Harbor" 400 



Bacilli of Group IV. : 



"Baltimore" (homologous) 3,200 



"Harris" 3,200 



"Gray" 3,200 



" Wollstein" 3,200 



We have described the above experiments of Hiss in considerable 

 detail not because we believe they represent the final classification of 

 the dysentery group, but because they illustrate the close antigenic 

 relationship of the dysentery bacilli and the relatively close correlation 

 between cultural and serological properties which they revealed. 



There seems to be little doubt about there being a large number of 

 different dysentery bacilli which vary from each other in minor charac- 

 teristics, and it is very difficult to be sure whether one is dealing with 

 permanent type differences or with temporary variations or suppressions. 

 For this reason-, it may be best to state definitely what the common 

 characteristics are which belong to organisms of this group and into 

 what main subdivisions they can be classified. 



All the dysentery bacilli are Gram-negative bacilli, usually slender, 

 but on occasion, especially in old cultures, short and plump, being mor- 

 phologically indistinguishable with certainty from typhoid or similar 

 bacilli.. There are all of them non-motile and non-spore bearing. They 

 do not liquefy gelatin. None of them produce gas on carbohydrate 

 media, none of them produce acid on lactose. 



They grow easily on the ordinary media, their colonies on agar and 

 gelatin being like those of typhoid but apt to be more delicate. On 

 broth they produce an even clouding and on differential media, like 

 those of Endo, Conradi-Drigalski, etc., they grow like typhoid but 

 rather more delicately. 



The main types into which they can be divided are the Shiga type, 

 the Flexner type, the Bacillus "Y" type of Hiss and Park and the 

 Strong type. By many observers, notably Park, the Shiga type is the 

 only one that is spoken of as the B. dysenteric, the other types being 



