348 TYPHOID FEVER 



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

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

 them to be excluded, and, therefore, as the b. dysenteric 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 and 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- 

 tion and abundance of polymorpho-nuclear leucocytes, and the 

 structure of the mucous membrane, as well as that of the 

 muscularis mucosae, is often lost in the exudation. There is 

 also great thickening of the sub-mucosa, with great infiltration of 

 leucocytes, these being chiefly of the character of " plasma cells." 

 In the more chronic forms the changes correspond, but are 

 more of a proliferative character. The mucous membrane is 

 granular, and superficial areas are devoid of epithelium, whilst 

 ulceration and pseudo-membrane are present in varying degree. 

 A feature of bacillary dysentery is the fact that abscess of the 

 liver does not occur as a complication. 



Agglutination. All the above-mentioned observers agree re- 

 garding the agglutination of this bacillus by the serum that is, 

 in the cases of dysentery from which the organism can be cul- 

 tivated. The reaction may appear on the second day, and is 

 most marked after from six to seven days in the acute cases ; it 

 is usually given in a dilution of from one in twenty to one in 

 fifty within an hour, though sometimes much higher dilutions 

 give a positive result. In the more chronic cases the reaction 

 is less marked, and here the sedimentation method is to be 

 preferred. It is difficult to make any general statements with 

 regard to the effects of dysenteric sera on the different strains 

 of the bacilli, but it may be said that generally a serum 

 agglutinates the strain which produced it and the other strains 

 of the same group in higher dilutions than it does the strains of 

 the other group. Many observers have found that the serum 

 from a case associated with strains of the Shiga-Kruse group 

 have not agglutinated strains of the Flexner group, and 

 corresponding observations have been made in cases associated 

 with the Flexner group. Often the sera of animals immunised 

 with bacilli have been used for such tests, but apparently great 

 care must be exercised in basing diagnoses on such observations, 

 for some species of animals when treated with a particular strain 



