BACILLI OF DYSENTERY 385 



macrophages, with red corpuscles, points to bacillary rather 

 than amoebic dysentery (Mackie). Another feature of bacillary 

 dysentery is the fact that abscess of the liver does not occur 

 as a complication. 



Agglutination. — There is- general agreement regarding the 

 agglutination of this bacillus by the serum — that is, in the 

 cases of dysentery from which the organism can be culti- 

 vated — and the reaction is of diagnostic value. The reaction 

 may appear on the second day, and is most marked after from 

 six to seven days in the acute cases. Agglutination of the 

 Shiga bacillus in an hour in a serum dilution of one in fifty is 

 usually accepted as being of diagnostic significance. The case of 

 the Flexner bacillus is much more difficult ; on the one hand, it 

 is susceptible to agglutination by normal sera to such an extent 

 that probably a positive result with dilutions more concentrated 

 than 1-100 cannot be taken as indicating the presence of 

 infection ; on the other hand, the individuality of a strain used 

 may be such that it is not agglutinated by sera originated by 

 other strains. In chronic cases the reaction is less marked 

 than in acute. 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. It has been generally found that the serum 

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

 not agglutinated strains of the Flexner group, and corresponding 

 results have been made in cases associated with the Flexner 

 group. The sera of animals immunised with the bacilli are 

 used for such tests, but great care must be exercised in their 

 application, as the sera vary in different instances as regards 

 their action on strains allied to that used for injection. As a 

 rule, an anti-Y serum agglutinates strains of the Flexner group, 

 but Martin and Williams found that one-sixth of the mannite- 

 fermenting dysentery organisms cultivated by them were not 

 agglutinated by a univalent-Y serum when first isolated, though 

 half of these acquired this property on cultivation. It is doubt- 

 ful whether a univalent serum can be got which will agglutinate 

 all mannite-fermenting types. Agglutination of a dysentery 

 bacillus has not been obtained with serum from cases other 

 than those of dysentery, nor has a similar bacillus been cultivated 

 from such sources. The reaction is also absent in those cases 

 of dysentery which are purely amoebic in nature. 



Pathogenic Properties. — The organism is pathogenic to guinea- 



2 5 



