Introduction. 



Since NicoLLK drew attention to the fact ttiat the agglutination of bacteria 

 by an agglutinating immune-serum depended upon the formation of a compound 

 between the agglutinating body, or agglutinine, of the serum, and the agglutinable 

 substance in the bacteria, and after Bordet and later Joos had proved that this 

 agglutination would not take place unless a salt were present, it has been custom- 

 ary to regard the process as a direct or indirect consequence of the union of 

 these three substances. Very various views, however, are held by different obser- 

 vers as to the precise nature of this union. Thus Gruber, and Neufeld, believe 

 that it is a simple chemical combination; Joos, that it resembles the formation of 

 a double salt; while Bordet states that the union is no more than a simple phys- 

 ical process of absorption, and that it brings about agglutination either directly 

 or in consequence of a change in the molecular attraction between the bacteria 

 and the fluid in which they are suspended. 



The application of Ehrlich's side-chain theory and its terminology to the 

 phenomena of agglutination has led to still further speculation as to the nature and 

 mode of action of the specific agglutinines, that is to say, of those occurring in 

 immune-sera. Ehrlich, Wassermann, and Kirstein, regard agglutinines as receptors 

 of the second order; Bail believes them to be receptors of the third order. Eisen- 

 berg & Volk appear to be uncertain whether they are receptors of the second order 

 or of the third, and describe the agglutinines as composed of two molecular groups, 

 the first a labile specific group causing agglutination, the second a more stable 

 group that serves to unite the agglutinine to the bacteria that are to be agglutin- 

 ated. Proceeding further, they state that an agglutinine can be converted partially 

 or entirely into an aggliitinoid by various physical or chemical agents, such as 

 heat, acids, or alkalies; and they compare the agglutinoids to Ehrlich's toxoids. 

 The discoveries of Eisenberg & Volk, Wassermann, and others, go to shew— that 

 the agglutinoids fall into two classes, the proagglutinoids and the synagglutinoids; 

 the former having an affinity greater than, the latter an affinity equal to, that of 

 the agglutinine for the agglutinable substance of the bacteria; while neither of them 

 is able to bring about agglutination by its own unaided action, yet their presence 

 in solution hinders agglutination by an agglutinine, since they unite with the bind- 

 ing groups of the bacteria, and thus prevent the agglutinine from doing so. 



29* 



