54 



Studies in Bacterial Variability. — On the Occurrence and Develop- 

 ment of Dys-agglutinable, Eu-agglutinable and Hyper- 

 agglutinable Forms of Certain Bacteria. [A Report to the 

 Medical Research Council.) 



By E. W. Ainley Walker. 



(Communicated by Prof. Georges Dreyer, F.B.S. Beceived October 12, 1921.) 



(From the Department of Pathology, University of Oxford.) 



Introductory. 



That different cultures of an agglutinable bacterium may exhibit wide 

 differences in relative agglutinability when tested with the same agglutinating 

 serum is a familiar fact. But the conditions on which these differences 

 depend remain to a great extent obscure. Yet a number of facts which bear 

 upon the problem have come to light in the course of investigations carried 

 out by various observers. 



A good many years ago the present writer showed (1901) (1) that if a 

 series of strains* of B. typhosus be employed in preparing a corresponding 

 series of agglutinating serums, each such serum is found to act more power- 

 fully upon its homologous culture than upon any of the heterologous strains. 

 It was, therefore, stated that the serums were not only specific for the species 

 of bacterium in question, but also special in each case to the particular strain 

 employed in its production. It also appeared that, so far as the evidence 

 went, the heterologous strains always fell into the same order of relative 

 agglutinability when tested with the different " special " serums. 



Somewhat similar results have recently been published by A. D. Gardner 

 (1920) (2), in connection with his investigation of Paratyphoid A. serums, and 

 he has shown that the peculiar sensitiveness of a given strain to agglutination 

 by serum prepared with that particular strain, which I had indicated by the 

 term "special" is, in part at least, a matter of velocity of reaction. The 

 phenomenon (so far as it depends on reaction rate) was, therefore, spoken of by 

 him as a " super-specific acceleration " of reaction. 



Since my own experiments were made before the introduction of the present 

 accurately standardised methods of determining agglutination titre, I had 



* In the use of the terms " strains " nothing is implied with regard to the cultures so 

 spoken of save that they have been obtained from different sources, derived by different 

 methods of cultivation, or selected in any way for a particular purpose. If they show 

 differences, it is a matter for investigation in each case, whether such differences are 

 permanent or fleeting. 



