THE DYSENTERY BACILLI 441 



Bacilli of Group II.: 



" Y" (homologous) 6,400 



"Ferra" 6,400 



"Seal Harbor 6,400 



Bacilli of Group IV.: 



" Baltimore " 1,600 



"Gray" 1,600 



"Harris" 1,600 



"WoUstein" 1,600 



Serum of Rabbit immunized against Gkoup IV. ("Baltimore" 

 culture) . 



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 



"WoUstein " 3,200 



In common, all these groups possess an identical morphology, the 

 Gram-negative staining characteristics, the lack of motility with close 

 adherence to the line of inoculation in the Hiss tube medium, the in- 

 ability to liquefy gelatin, the inability to form acid from lactose, and 

 the inability to produce gas from any carbohydrate media. 



Biological Considerations. — The dysentery bacilli in neutral broth 

 or upon agar slants may remain alive without transplantation for 

 periods of several months. They are aerobes and facultative anaerobes 

 when proper sugars are present, preferring, however, the aerobic environ- 

 ment. They are easily destroyed by heat, an exposure to 60° C. killing 

 them usually in a short time (ten minutes) . Against cold they show 

 considerable resistance,. surviving freezing for a period of several weeks. 

 They show little resistance to the usual strengths of the common chem- 

 ical disinfectants. 



Pathogenicity. — There is practically no doubt at the present time as to 

 the etiological connection between the bacilli of this group and the dis- 

 eases clinically classified as acute dysentery. A more chronic form of 



