VII. THE MECHANISM OF AGGLUTINATION * 



BY DR. JULES BORDET. 



The expression "phenomenon of agglutination" is usually em- 

 ployed to indicate that bacteria, in a homogeneous suspension in a 

 fluid like bouillon or isotonic salt solution collect in clumps and 

 fall to the bottom of the tube when acted on by a specific serum. 

 We demonstrated the first instance of this phenomenon in 1895 

 by showing that cholera vibrios suspended in salt solution lose 

 their motility when subjected to the action of a small dose of fresh 

 or heated anticholera serum and that they then rapidly collect in 

 small masses that float in the fluid. f 



This agglutination must be considered from several different stand- 

 points. In the first place it must be studied as an entity without 

 any reference to its physiological significance. When looked at 

 from this viewpoint agglutination has evident relation both with 

 physics and with chemistry. If we attempt to define the importance 

 of this phenomenon in immunity, when we wish, for instance, to 

 know whether it is functional in defense of the animal body or what 

 cells secrete the substances that cause it and liberate them in the 

 serum and so endow it with its particular activity, we must con- 

 sider agglutination from the physiological standpoint. 



In the present study we shall consider the mechanism of agglu- 

 tination and shall begin by reviewing the principal theories that have 

 been offered to explain the phenomenon. We may note at once 

 that, to be satisfactory, a theory on a subject like this should have 

 a general bearing, and should not deal simply with the agglutination 

 of bacteria. Bacteria are not the only cells clumped by serum; 

 the agglutination of red blood cells by the serum of an animal of 

 another species, must also be taken into consideration. We have 



* Le mdchanisme de 1'agglutination. Annales de 1'Institut Pasteur, 1899, 

 XIII, 225. 



t See article, p. 8. 



142 



