398 TYPHOID FEVER 



themselves into two chief groups, whose differences lie in their 

 behaviour towards certain sugars, in their capacities of forming 

 indol, and in their agglutinating reactions. The relation of 

 amoebae to dysentery will be discussed in the Appendix. 



Bacillus Dysenteriae. Morphological Characters. This 

 bacillus morphologically closely resembles the typhoid bacillus, 

 but is on the whole somewhat plumper, and filamentous forms 

 are comparatively rare. Involution forms sometimes occur, 

 especially in glucose agar. Most observers have found no trace 

 of motility, whilst others say that it is slightly motile. Vedder 

 and Duval have, however, demonstrated in the case of one strain 

 the presence of numerous lateral flagella, which are of great 

 fineness, but of considerable length. No spore formation occurs ; 

 the organism is stained readily by the ordinary dyes, but is 

 decolorised by Gram's method. 



Cultural Characters. In these also considerable resemblance 

 is presented to the typhoid bacillus. In gelatin a whitish line of 

 growth occurs along the puncture, but the superficial film-like 

 growth is usually absent, or at least poorly marked. In plate 

 cultures the superficial growths have often the vine-leaf contour 

 of typhoid colonies, but they are more slimy. On agar, growth 

 occurs as a smooth film with regular margins, but after two or 

 three days, especially if the surface be moist, Vedder and Duval 

 describe an outgrowth of lateral offshoots on the surface of the 

 medium. On agar plates the colonies resemble those of the 

 typhoid organism, being of smaller size and less opaque than 

 those of the bacillus coli. In peptone bouillon a uniform haziness 

 is produced. As has been indicated, different strains of the 

 bacillus behave differently towards different sugars, and the 

 results of all observers do not agree, so that only general state- 

 ments can be made. Without going into the question of the 

 particular strains to be placed in the two groups, we may say 

 that, roughly, these may be classified into the Shiga-Kruse group 

 and theFlexner group. All produce acid in peptone-glucose and 

 in taurocholate peptone-glucose ; none produce change in lactose. 

 The Shiga group do not produce acid in maltose or mannite, 

 while the Flexner group do, and, generally speaking, the former 

 do not produce indol, while the latter do. Forms intermediate 

 between the two groups occur, and special attention has been 

 directed to a " Y " strain which does not ferment maltose. There 

 is never any evolution of gas observed in sugar media. In litmus 

 milk there is developed at first a slight degree of acidity, which 

 is followed by a phase of increased alkalinity ; no coagulation of 

 the milk ever occurs. On potato the organism forms a transparent 



