386 TYPHOID FEVER 



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. McConkey's agar medium with 

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

 the fa3ces is rubbed up in broth and some of the mixture stroked 

 on the medium. The formation of acid by the b. coli colonies 

 enables them to be excluded, and therefore, as the b. dysenteriye 

 is not a lactose fermenter, the colourless colonies which develop 

 after twenty -four hours are picked out for further investigation. 



As already stated, both acute arid chronic cases are marked 

 by the presence of this organism. In the former, where death 

 may occur in from one to six days, the chief changes, according 

 to Flexner, are a marked swelling and corrugation of the mucous 

 membrane, with haemorrhage and pseudo-membrane at places. 

 There is extensive coagulation-necrosis with fibrinous exuda- 



