FITZGERALD AND FRASER 823 



wright, and the distinctive antigens of these variants, were concerned in the cross- 

 agglutination of the two bacterial species. As interpreted by serological relationships, 

 antigenic structure, if one may justifiably apply a solid term to such a delicate and 

 phantom fal^ric, has become kaleidoscopic — to use a simile of Andrewes. Tulloch,' 

 in reviewing the present position of bacterial agglutination, concludes in part: 



In the present state of ignorance it is inadvisable to employ the procedure known as 

 receptor anal\'sis in order to investigate bacterial genetics and the antigenic relationship of 

 micro-organisms to one another. The use of the procedure involves the assumption that each 

 reaction observed is referable to a separate constituent of antigen and a separate moiety of 

 antibody. There is no evidence whatsoever that this assumption is valid. 



It is largely by means of the phenomenon of agglutination, in respect of the as- 

 sumed correlation between the in vitro results of in vivo experiments, that a picture 

 of the apparent complexity of antigens is revealed — a picture which perhaps presents 

 today more the aspect of an incompleted jig-saw puzzle than the finished work of art 

 of tomorrow. 



SUMMARY 



In viewing the subject, agglutinins and their application, as a whole, certain facts 

 are apparent. First, the reaction is specific in that, when adequately controlled and 

 precisely carried out, differences in the identity of micro-organisms, too slight and too 

 subtle to be appraised by cultural and biochemical methods, may be established. 

 These dififerences have not only a theoretical interest but may, in certain instances, 

 serve as a basis of more selective and more rational serum therapy, on the one hand, 

 and, on the other, correlate epidemiological data with clinical findings. Further, 

 among certain other species of micro-organisms, strains with distinctive and definite 

 agglutinative characteristics are yet so closely related in their pathogenicity that one 

 measurable antibody response (antitoxin) is identical for all strains. Second, the 

 methods of the technique of measuring agglutination have been developed to an 

 extraordinary degree of delicacy. Third, the fact of bacterial variation, the interpreta- 

 tion of which is still incomplete, introduces a new problem in respect of the applica- 

 tion of the phenomenon of agglutination. Fourth, of recent years, much speculative 

 philosophy has been brought to bear in order to correlate the antibody response as 

 revealed by in vitro reactions with the structural components of its antigen. Fifth, 

 the fundamental fact of the specificity of antigen-antibody reaction is as much a 

 mystery as ever. 



' Tulloch, W. J.: /. Roy. Army M. Corps, 48, 435. 1927. 



