CHEMICAL METHODS IN THE ANALYSIS OF ANTIGENIC STRUCTURE 279 



phase ; those that possessed the specific antigen only as being in the specific phase. 

 If repeated plate cultures were prepared from a strain that was in the specific 

 phase, bacilli in the group phase turned up sooner or later ; similarly a strain in 

 the group phase gave rise to sub-strains in the specific phase. The variations might 

 occur in either direction. Species or types of bacteria that show this curious 

 variation in their flagellar antigens are termed diphasic. For completeness, we 

 should note the association of one other type of bacterial change, not strictly a 

 variation, with change of antigenic structure ; namely, the transformation of a 

 vegetative form into a spore. Not only is there a transformation of antigenic 

 structure (Howie and Cruickshank 1940), but the characterization of the spore 

 antigens reveals relationships between bacteria that are not evident on the basis 

 of the vegetative forms of the antigens (Lamanna 1940). We do not know of 

 any example of true diphasic variation affecting the somatic antigens. 



In diphasic variation, the antigenic constitution of the flagella does not always 

 alternate between a " specific " and a " group " phase. In some of the diphasic 

 Salmonella types the alternate phase possesses antigens that characterize the 

 " specific " phases of other Salmonella types (Kauffmann 1936, Kauffmann and 

 Tesdal 1937, Kauffmann 1939). Kauffmann used the notation a — >-/S variation 

 to distinguish it from the commoner type of diphasic variation. The ^ phases 

 have nothing in common with flagellar " group " phases, but they are relatively 

 restricted in range, all being characterized by two antigens, and most of them 

 possessing one of three subsidiary antigens (see Chapter 30). It may be noted that 

 the H and antigens vary independently. Thus, Boivin and Mesrobeanu (1937) 

 induced the following six variants in Salm. typhi-murium— smooth + specific H, 

 smooth + group H, smooth ; and rough + specific H, rough + group H, 

 rough 0. (See also Boivin, Izard and Sarciron 1939.) 

 The Application of Chemical Methods in the Analysis of Antigenic Structure. 



A few examples will suffice us here, since the chemical constitution of the 

 antigenic components that characterize the various species of bacteria is described 

 more fully, where it is known, in the chapters devoted to systematic bacteriology. 



Zmsser and Parker (1923) isolated substances from pneumococci, staphylococci, the 

 influenza baciUus, the typhoid bacillus and the tubercle bacillus, which gave none of the 

 ordinary protein reactions, except a very weak xantho-protein reaction, but gave specific 

 precipitation and complement fixation with the corresponding antisera prepared by the 

 injection of whole organisms. These non-protein antigens failed to stimulate antibody 

 production on injection. 



In the same year Heidelberger and Avery pubhshed the first of a series of papers dealing 

 with a chemical study of the antigenic constituents of the pneumococcus (Heidelberger 

 and Avery 1923, 1924, Avery and Heidelberger 1923, 1925, Avery, Heidelberger and Goebel 

 1925, Avery and Morgan 1925, Avery and Neill 1925). From the three classical types of 

 pneumococci, in their normal smooth form, partial antigens were separated, which were 

 found to have the chemical structure of complex polysaccharides, failed to stimulate 

 antibody production in vivo, but gave specific precipitation at extraordinarily high dilutions 

 when mixed with antisera prepared by the inoculation of rabbits with the corresponding 

 strains of pneumococci. 



In rough variants, which are non-capsulated, these polysaccharide antigens are absent ; 

 but there remains a protein antigenic component which is common to the rough variants 

 of all types, and is also present in the smooth capsulated forms, though in these their 

 presence is masked by the type-specific capsular polysaccharide. 



The history of the pneumococcal polysaccharide illustrates one of the drawbacks of 



