THE AGGLUTININS 2Og 



combination with the bacteria. Further, it is clear that we may 

 distinguish two properties of agglutinin (that of uniting with antigen 

 and that of clumping), and that these are discharged at different 

 temperatures : the agglutinin unites at o, and only exerts its 

 specific action at higher temperatures. We may express this in 

 Ehrlich's terminology by saying that it possesses a haptophore 

 group which functionates at o, and an ergophore group which 

 only acts in the warm. 



Another proof is as follows : It was shown by Bordet that 

 agglutination only takes place when certain salts are present. Of 

 these sodium chloride appears to be the most generally efficient, 

 but Crendiropoulo and Amos have shown the calcium chloride 

 has a special adjuvant action in the agglutination of cholera 

 vibrios. To this subject we shall return. The proof of the union 

 between bacteria and their agglutinins is made as follows: 

 Bacteria are added to clumping serum, and the precipitate collected 

 and washed and shaken in a large quantity of distilled water. 

 No agglutination occurs until salt is added, when it takes place 

 rapidly, according to the thickness of the emulsion. In this case 

 also the two substances must have entered into the combination. 



The substance with which agglutinin combines i.e., that 

 which calls forth its production in the living animal is evidently 

 not a toxin, since an agglutinating serum has, as such, no protec- 

 tive action. We know some of its characters. It is formed, of 

 course, in the bodies of the bacteria, and in young cultures is 

 entirely intracellular. In older cultures, however, it diffuses out, 

 being probably set free by a process of autolysis, and passes into 

 solution. This is especially the case in broth cultures, and this is 

 one of the reasons why, if liquid cultures are used in agglutination 

 tests, they must be young ; in agar cultures there is less diffusion 

 of the agglutinable substance, and the need is not so great. Its 

 presence may be proved in two ways : In the first place, this 

 filtrate, if injected into animals, will bring about the production 

 of agglutinin, as we should expect. In the second place, this 

 fluid, when added to a powerful clumping serum, will cause a 

 precipitate. This is Kraus's reaction, and it is a most interesting 

 phenomenon. It is best seen when the fluid portion of broth 

 culture of B. typhosus or V. cholera (at least a month old and 

 filtered through a Berkefeld filter to remove all solid particles) is 

 added in various proportions to a strong immune serum. Under 

 such circumstances the fluid will gradually become opalescent, or 



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