AGGLUTINATION. 211 



that the agglutinating property, as well as the bac- 

 tericidal power, was the result of immunization. 

 Inasmuch as an increase in the bactericidal power 

 of a serum points to the existence of an acquired 

 immunity,, the question naturally arises : Does the 

 associated property of agglutination have a similar 

 significance ? 



Many observations indicate that the two activi- 

 ties are distinct, that they depend on different 

 substances in ~the serum. The following are the 

 important points involved : 



1. The bactericidal power is destroyed at 56 C.. 

 while agglutinins resist a temperature of 62 C. 



2. In certain cases it has been possible to cause 

 the bacteria to absorb the agglutinin from the 

 serum, leaving the bactericidal substance intact. 



3. A serum may be bactericidal, but not agglu- 

 tinating. 



4. During the course of natural or experimental 

 typhoid fever or cholera the development of the 

 agglutinating and bactericidal powers may not be 

 parallel. In cholera, the agglutinating power may 

 disappear soon, but the bactericidal power remains 

 for a long time. 



5. Micro-organisms which have been killed by a 

 bactericidal serum may lose their toxicity; ag- 

 glutinated bacteria remain virulent. 



Besredka found an apparent relationship be- 

 tween agglutination and immunity; if typhoid 

 bacilli were agglutinated before they were injected 

 into the abdomen of a guinea-pig the animal would 

 recover, but if they were not agglutinated death 

 resulted. The explanation offered for this loss of 

 virulence is that the bacilli being agglutinated and 

 immobilized are more readily taken up by the 



