144 ANTIGENS AND THE TECHNIC OF SERUM REACTIONS 



eventually clumping. Smith and Reagh 1 working with a non-motile 

 hog cholera bacillus have demonstrated both flagella and somatic 

 agglutinins, the former paralyzing the activity of the flagella, the 

 latter agglomerating the organisms themselves. Non-motile bacteria 

 usually agglutinate somewhat more slowly than motile organisms. 

 Small amounts of neutral salts are necessary for the clumping of 

 bacteria, 2 although a union of the specific organism and its agglutinin 

 will take place even if salts are absent. The specific substance (or 

 substances) of the bacterial cell which reacts with the specific antibody 

 of the serum (agglutinin) is known as agglutinogen. Closely related 

 bacteria, as typhoid and paratyphoid bacilli, may possess a certain 

 amount of agglutinogen in common, but, as a rule, the specific 

 organisms are clumped in immune sera at much, greater dilution than 

 related organisms are clumped. Also, the specific organisms will 

 remove the agglutinin completely from immune sera, while closely 

 related bacteria only remove that portion of the agglutinating sub- 

 stance which is common to both organisms, leaving behind the 

 specific agglutinin which will then agglutinate the specific organism, 

 but not its closely related fellow; that is to say, closely related 

 bacteria will react with the common or group agglutinin, but fail to 

 absorb the specific agglutinin. 



Experience has shown that the sera of normal adults frequently 

 contain agglutinin which will clump various bacteria and the potency 

 of these "normal" or natural agglutinins may even be sufficient to 

 clump moderate numbers of typhoid bacilli in dilutions as great as 

 1 to 30. The sera of normal nurslings contain only minimal amounts 

 of normal agglutinins as a rule, and the conclusion has been drawn 

 that normal agglutinin may be either: 



(a) Group agglutinin, derived from mild infection with closely 

 related organisms, or 



(6) True immune agglutinins resulting from mild or unrecognized 

 infection with the specific organism. 



No definite distinction has been noted between natural and immune 

 agglutinins; the latter are usually present in sera, however, in much 

 greater concentration than the former. 



The site of formation of agglutinins in the body is not definitely 

 known, although lymphoid tissues appear to be intimately concerned, 

 especially bone-marrow and the spleen. Pryzgode 3 states that 



1 Jour. Med. Res., August, 1903, x, No. 1. 



2 Bordet, Collected Studies in Immunity, 1909 (translation by Gay). 



3 Wien. klin. Wchnschr., 1913, xxvi, 84. 



