AGGLUTININS 95 



infection. Why this should be is not clear, unless we assume that 

 the organisms have developed new characteristics, in consequence of 

 which they are no longer open to attack by the bacteriolysins of the 

 serum, and that the subsequent defence of the body must be carried 

 on by other forces. For the correctness of this view there is some 

 actual basis (see preceding chapter), but even so the last word on 

 the use of the bacteriolytic sera has probably not yet been spoken. 



But in any event the discovery of the bacteriolysins must be 

 regarded as one of the greatest importance, as it has enabled us to 

 gain a certain insight into the defensive mechanism of the animal 

 body, which is most essential to further advance. Practically 

 important is the fact that the action of the bacteriolytic immune 

 amboceptors is specific and thus permits of a twofold diagnostic 

 application. As the amboceptor content of the immunized animal 

 is always higher than that of the normal control, a higher titer in 

 reference to a given organism may be regarded as evidence of a 

 preceding infection. Similarly one can use an immune serum for 

 the purpose of identifying a given organism by comparing its action 

 with that of a normal serum upon the organism in question, in the 

 peritoneal cavity of a guinea-pig. Both methods are in actual use, 

 the first for ascertaining whether or not an individual has recently 

 passed through an attack of cholera, the other for establishing the 

 identity of the corresponding organism after its isolation from the 

 feces. (For a description of the method see Diagnostic Bacteriolytic 

 Reactions.) 



Agglutinins. The next group of antibodies was discovered by 

 Gruber and Durham (1896). These are termed agglutinins from the 

 fact that the sera in question, when brought together with emulsions 

 of the corresponding organisms, will cause the "clumping" or agglu- 

 tination of the bacteria, and if these are normally motile, incidentally 

 affect their loss of motility. As this property also is specific within 

 certain limitations and the technique involved in its demonstration 

 very simple, the principle has been extensively utilized for diagnostic 

 purposes. As in the case of the bacteriolysins it may be applied 

 both for the identification of a given organism and in search for the 

 corresponding agglutinin. Under -the name of the Widal reaction the 

 test is now used the world over as one of the most importantjactors 

 in the diagnosis of typhoid fever (see Agglutination Reaction). 



The significance of the process of agglutination is not very clear. 



