28(3 INFECTION AND IMMUNITY 



is entirely analogous to the clumping of colloidal suspensions of 

 any kind, and if we consider that bacterial suspensions are in many 

 other respects similar to colloidal suspensions, namely, in their 

 negative charge and their wandering to the positive pole in neutral 

 solutions, in kataphoresis experiments, it becomes apparent that the 

 actual clumping or agglutination is a purely physical phenomenon, 

 determined by the colloidal equilibrium of the bacteria in suspension. 



Altogether, we ourselves are inclined to regard the so-called 

 agglutinins as identical with other sensitizers, and the actual clump- 

 ing as a colloidal precipitation of organisms that have been altered 

 in their suspension equilibrium as a result of the union with the 

 antibodies together with some serum protein. 



Agglutinated bacteria 22 are not killed by the act of agglutination 

 and are often as virulent as non-agglutinated cultures. Metchnikoff 

 assigned to them a secondary role in relation to protection, but 

 it is quite likely from more recent observations, that they do par- 

 ticipate distinctly in the protective mechanism. Recent work by 

 Bull seems to indicate that bacteria are agglutinated in vivo as a 

 sort of preliminary step to phagocytosis. 



The agglutinins, furthermore, unlike the bactericidal substances 

 in sera, remain active after exposure to temperatures of over 55 C., 

 some of them withstanding even 65 to 70, and can not be reac- 

 tivated by the subsequent addition of normal serum. These facts 

 definitely preclude the participation in the reaction of the alexin 

 or complement. 



Production of Agglutinins. Just as normal sera contain small 

 quantities of bactericidal substances, so do they contain agglutinins 

 in small amount. In a general way these "normal agglutinins" 

 have the same nature as the immune agglutinins, and their presence 

 is probably traceable to the various microorganisms parasitic upon 

 the human and animal body. 



As a matter of fact, the blood serum of new-born guinea-pigs 

 hardly ever contains agglutinin for B. coli, while that of adults 

 acts upon these bacilli in dilutions of 1 :20. 23 Similarly, infants 

 show lower normal agglutinating values than adults. 24 



Agglutinins may be produced in the sera of animals by the intro- 



22 Mesnil, Ann. de 1'inst. Pasteur, 1898. 



2S Kraus und Low, Gesell. d. Aerzte, Wien, 1899. 



"Pfaundler, Jahrb. f. Kinderheilk,., Bd.-50. 



