BACILLUS DYSENTERIC 347 



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

 cultures also the superficial growths are smaller and have less of 

 the film-like character, than those of the typhoid organism. 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 

 statements 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 the Flexner group. All produce acid in peptone-glucose and 

 in taurocholate peptone-glucose, none produce change in lactose or 

 cane-sugar. 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 inter- 

 mediate between the two groups occur. 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 or 

 whitish layer, which, however, in the course of a few days assumes 

 a brownish-red or dirty grey colour, with some discoloration of 

 the potato at the margin of the growth. 



Relation to the Disease. The organism has been found in 

 large numbers in the dejecta, especially in the acute cases, where 

 it may be present in almost pure culture. In the thirty-six cases 

 examined, Shiga obtained it in thirty-four from the dejecta, and in 

 the two others post mortem from the intestinal mucous membrane. 

 The organism does not appear to spread deeply or to invade 

 the general circulation. In the more chronic cases it is difficult 

 to obtain on account of the large number of the bacillus coli and 

 other bacteria present. Vedder and Duval found agar plates to 

 be the best method of culture, these being incubated at the 

 blood temperature. They also found that if the colonies which 

 appeared at twelve hours were marked with a pencil, there was 

 a greater probability of obtaining the bacillus of dysentery from 

 those which appeared later, most of those appearing early being 

 colonies of the bacillus coli. MacConkey's agar medium with 

 lactose added may be used for isolation from stools. A little of 



