THE PHENOMENON OF AGGLUTINATION 235 



56 C.), as a rule agglutinins will not disappear from serum until 

 the temperature is raised to between 70 and 80 C. Once de- 

 stroyed, however, no reactivation takes place upon the addition of 

 fresh normal serum. Ehrlich, for this reason, has conceived the 

 structure of agglutinins as "Ilapiines of the Second Order," in 

 which he supposes that the zymophore and the haptophore groups are 

 inseparably connected, and in which we could assume an alteration 

 of the less stable zymophore group without interference with the 

 functional integrity of the haptophore group. Such an altered ag- 

 glutinin could be spoken of as "agglutinoid," and this could become 

 united with a bacterial cell without 

 inducing agglutination, but, by its 

 union, prevent subsequent combina- 

 tion of the cell with unaltered agglu- 

 tinin. This process of "agglutinoid 

 Yerstopfung" has been held respon- 

 sible for the failure of agglutination 

 when bacteria that have been in con- 

 tact with heated serum are subse- 

 quently exposed to the action of ac- 



tively agglutinating serum. It is 



^ i ;? t . -i i i DIAGRAMMATIC REPRESENTATION OF 



assumed that the agglutmoids which EHRLICH 's CONCEPTION OF THE 



were present in the heated serum STRUCTURE OF AGGLUTININ. 



have occupied the bacterial receptors 



and have thereby prevented the union of these with the agglutinins 

 later added. 



The work of Eisenberg and Yolk 51 has gone very thoroughly 

 into these conditions and forms the strongest bulwark of this point 

 of view. These workers showed that bacteria thus exposed have 

 not only become less sensitive to agglutinins, but have, at the same 

 time, lost much of their power to absorb agglutinins when compared 

 with normal bacteria. The same loss of agglutinating power which 

 is observable in heated agglutinating serum is evident to a lesser 

 extent in serum w r hich has been preserved at room temperature. 

 Eisenberg and Yolk have shown that such serum, in addition to a 

 loss of its total agglutinin content, loses the power to agglutinate 

 in high concentrations. Thus a serum which has been preserved in 

 this way will no longer agglutinate bacteria in concentrations of 1 

 to 20, 1 to 40, or even 1 to 100, but will agglutinate as before in 

 higher dilutions. This is taken to mean that the agglutinoids formed 

 during the period of standing possess a higher affinity for the bac- 

 terial antigen than do the true unaltered agglutinins. Since these 

 so-called "proagglutinoids" are relatively small in amount, their 

 action is masked when considerable dilution has sufficiently di- 

 minished their quantity, in proportion to the more plentiful un- 



51 Eisenberg and Volk. Zeitschr. f. Hyg., Vol. 40, 1902. 



