494 PATHOGENIC BACTERIA. 



0.5 c.cm. of distilled water, and add to it a drop or two of a six- 

 day-old culture of the same bacillus, a drop of it allowed to stand 

 for a few hours in a moist chamber, when examined under the 

 microscope, will show typical agglutinations. The addition of a 

 little distilled water will have the same effect ; hence the infer- 

 ence is drawn that the reaction is a passive, not an active, histo- 

 genic one." 



IX. The specific nature of the reaction is now univer- 

 sally accepted. There are, however, certain cases of 

 irregular phenomena which diminish the absolute reli- 

 ability of the test. These may or may not be dependent 

 upon conditions which it is within the province of expe- 

 rience to explain. 



Normal human serum, when concentrated, occasion- 

 ally exerts a slight agglutinating effect upon the typhoid 

 bacillus. This seldom occurs except with concentrations 

 exceeding those employed for diagnostic purposes. • 



The blood of certain animals normally possesses an 

 agglutinating property for the typhoid and other bacilli. 

 Some individuals are peculiar in that their blood acts 

 more strongly in its agglutinating and bacteriolytic action 

 than others. 



A few diseases, which may or may not be related to 

 typhoid, occasionally produce in the blood of their vic- 

 tims a reactive effect upon the typhoid bacillus. The 

 number of cases in which such errors can occur is shown, 

 by reference to the statistics of Pepper, Stengel, and 

 Kneass (given above), to be very small, and the validity 

 of the test is very slightly influenced by them. It will 

 be shown elsewhere that for a final opinion upon the 

 specificity of any reaction attempted for purposes of 

 scientific diagnosis certain definite criteria are given 

 which allow of little or no deviation, and to which 

 non-conformity by those reporting irregularities must 

 be submitted before their weight is established. 



Villiez and Battle ' found that in three cases of malaria 

 from Madagascar a positive reactive phenomenon oc- 

 curred in one. 



1 Presse ?neJ., 1896, No. 84. 



