172 BACTERIOLOGICAL EXAMINATION OF WATER. 



by the anti-typhoid serum in the high dilution of 1-100,000 

 (the table, however, shows several specimens of B. typhosus 

 which were not agglutinated by dilutions beyond 1-10,000). 

 The typical B. coli of Escherich varied extremely in its reaction 

 to the serum ; some were only agglutinated by a dilution of 

 1-10, others reacted to a dilution of 1-10,000. Taking Beco's 

 results as published by him in the above table, the agglutination 

 test would not appear to be an infallible means of diagnosis, as 

 varieties of B. coli and B. typhosus were agglutinated by the 

 same dilution of the anti-typhoid serum. 



Jatta has quite recently re-investigated this subject and 

 arrived at some important results. He found that the serum 

 of animals immunised by injections of B. typhosus agglutinated 

 this organism more strongly than twenty-eight different speci- 

 mens of B. coli which he investigated. The serum behaved 

 very differently to the various specimens of B. coli ; the results 

 Jatta obtained are shown in the following table : 



Serum of an immunised dog : 



When diluted 1-10,000, agglutinated the B. typhosus. 



When undiluted, had no action on fifteen out of the twenty-four 



cultures of B. coli. 



When diluted 1-10, agglutinated one specimen of B. coli. 

 When diluted 1-100, agglutinated five specimens of B. coli. 

 When diluted 1-300, agglutinated four specimens of B. coli. 



Serum of an immunised sheep : 



When diluted 1-1,000, agglutinated the B. typhosus. 

 When undiluted, had no action on ten specimens of B. coli. 

 When diluted 1-10, agglutinated five specimens of B. coli. 

 When diluted 1-30, agglutinated six specimens of B. coli. 

 When diluted 1-100, agglutinated seven specimens of B. coli. 



The serum of a typhoid patient when tested with the speci- 

 mens of B. coli. gave the following results : 



Serum of patient : 



Diluted more than 1-300, agglutinated the B. typhosus. 

 Diluted 1-300, agglutinated seven specimens of B. coli. 

 Diluted 1-100. agglutinated four specimens of B. coli. 

 Diluted 1-10, agglutinated four specimens of B. coli. 



Jatta's observations appeared to show that as the aggluti- 

 nating action of the serum on the B. typhosus increased or 

 diminished, the action on B. coli also increased or diminished. 

 The serum of the immunised dog, mentioned above, tested 



