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Mr. H. R Deau. 



[Oct, 13, 



Bordet and Gengou (1911) published a paper dealing with a phenomenon 

 which they have named co-agglutination, and which they have expressly 

 stated is to be clearly distinguished from conglutination. They found that 

 a mixture of antigen and antibody is able to produce a very marked agglutina- 

 tion of the red cells of a third animal, the guinea-pig. The conditions under 

 which this co-agglutination occurs are carefully set forth by the authors. 

 Guinea-pig blood was found to be the only sort of blood which gave 

 satisfactory results. Defibrinated guinea-pig blood was, as a rule, employed, 

 but equally satisfactory results could be obtained by the use of a suspension 

 of washed corpuscles. Both the serum which contained the antigen and 

 the serum which contained the antibody were heated to 56° C. before use. 

 The co-agglutination was obtained with all the antigen-antibody systems 

 used by the authors. As the co-agglutination was obtained by the use of 

 heated sera and washed guinea-pig corpuscles, the participation of com- 

 plement could be excluded. Co-agglutination only occurred if a considerable 

 excess of antigen relative to antibody was present in the mixture. The 

 proportions most favourable to co-agglutination were such that the antigen 

 was present in such excess as to inhibit the formation of a precipitate. 

 When the proportions were such that a marked precipitate formed, 

 co-agglutination did not occur. The co-agglutination was not accompanied 

 by any marked fixation of complement. It was necessary that the guinea- 

 pig corpuscles should be present at the time when the antigen came into 

 contact with the antibody. To produce this result the corpuscles were 

 mixed with the antigen and the antibody was then added. Under the 

 proper conditions the agglutination of the red corpuscles was not only 

 very marked but very persistent, that is to say, the corpuscles could be 

 shaken up an indefinite number of times and invariably re-agglutinated. 



It would thus appear that the clumping or agglutination of red cells may 

 take place under three different sets of conditions : — 



(1) Agglutination. — By this is meant the well-known clumping of red cells 

 by a specific antiserum or by a normal serum which possesses agglutinins for 

 the red cells employed. 



(2) Conglutination. — This is produced by the action of ox colloid (con- 

 glutinin) on cells which have been treated with homologous antiserum and 

 with complement. In place of a serum prepared by the injection of an 

 animal with red cells, a normal serum which contains a normal agglutinin 

 for the red cells can, however, be employed. 



(3) Co-agglutination. — An antigen and homologous antibody can under 

 appropriate conditions agglutinate the red cells of another animal (preferably 

 a guinea-pig). 



