L— THE INFLUENCE OF IMMUNE SERUM ON THB 

 BIOLOGICAL PROPERTIES OF PNEUMOCOCCAL 



By Fred. Griffith, M.B. 



More exact knowledge of the natural variations in virulence 

 and antigenic qualities which pathogenic bacteria may undergo 

 is needed for two main purposes. In the study of epidemiological 

 problems this information forms a necessary part of the data 

 which should be established ; and for the purpose of serum and 

 vaccine therapy it is equally important to know in what respects 

 immunological characters may be influenced by transfer of the 

 bacterium from the animal body to the test tube and by culture 

 on different media. 



The conception of a " pure culture " of a bacterium as a 

 number of absolutely identical individuals is no longer tenable. 

 Arkwright,* in a recent interesting and suggestive article on the 

 subject of variation in bacteria, with particular reference to 

 B. dysenterice (Shiga), B. typhosus, B. paratyphosus B. and 

 B. enteritidis, has shown that, in all the cultures he has worked 

 with, two forms almost invariably make their appearance under 

 certain conditions. These he has designated R (rough), and 

 S (smooth), owing to the distinctive characters of their colonies 

 on agar plates. Further important differences between the two 

 are that each form appears to have a different main antigen, both 

 of which are present in the parent stock; and the R form, unlike 

 the S, does not form a stable emulsion in 0*85 per cent, solution 

 of sodium chloride. In the bacterial species upon which Ark- 

 wright reports the normal, at any rate superficially, resembles 

 more nearly the S form, the R form being the " variant." 



Beniansf had previously recorded similar changes in a culture 

 of dysentery (Shiga) bacilli. 



Mary CowanJ has described similar varieties of colonies in 

 cultures of streptococci; she states that "individual strains of 

 streptococci can be ' dissociated ' into ' rough ' and ' smooth ' 

 types which show remarkable differences in virulence for labora- 

 tory animals." 



Andrewes,§ in his investigation of the serological types in 

 the Salmonella group, has also obtained two varieties of colonies 

 from the same strain. In this case the colonies are identical in 

 appearance but show differences in their immunological reactions ; 

 in the one form the antigen which evokes and reacts with the 

 specific agglutinins is dominant, whereas the capacity to produce 

 and react with the group -agglutinins is dominant in the other. 

 Although Andrewes finds that the colonies of the two types are 



* Journ. Path, and Bact., XXIV., p. 36, 1921. 

 f Journ. Path, and Bact., XXIII., p. 171, 1920. 

 X British Journ. Exper. Path., III., p. 187, 1922. 

 § Journ. Path, and Bact., XXV., p. 505, 1922. 



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