BACILLUS TYPHOSUS 519 



Widal reaction for the diagnosis of typhoid fever the results 

 are reported to have been almost uniformly satisfactory. In 

 the great majority of cases the reaction is, so far as experi- 

 ence indicates, specific i. e., a typical reaction does not 

 occur between typhoid serum or blood and organisms other 

 than the typhoid bacillus, nor between the typhoid bacillus 

 and serums other than those from cases of typhoid fever. 

 There are, however, confusing reactions so-called pseudo- 

 reactions in which more or less clumping of the bacilli 

 and a diminution of motion, without complete cessation, 

 are observed. These reactions have been seen to occur 

 with normal blood and with blood from other febrile con- 

 ditions. It is said by Johnston and McTaggart 1 that they 

 can be prevented if cultures of just the proper degree of vitality 

 are employed; and this corresponds with the results of a 

 fairly wide personal experience with the test. 



In the light of present experience it is fair presumptive 

 evidence that the serum is from a case of typhoid fever 

 when unmistakable agglutination and cessation of motion 

 are seen in from fifteen to twenty minutes after typhoid 

 bacilli are mixed with the serum of a conspicuous febrile 

 condition. 



The blood of certain animals, as well as a number of 

 chemical substances, such as corrosive sublimate, alcohol, 

 salicylic acid, resorcin, and safranin in high dilution, cause 

 agglutination of the typhoid bacilli; but the reaction is 

 not specific, for in most cases they have the same effect on 

 other motile bacilli. 



Drinking Water. All the points with regard to morpho- 

 logic and biologic characters of bacillus typhosus, and of 

 the organisms closely resembling it, should be borne in 



1 Montreal Medical Journal, March, 1897. 



