384 IMMUNOLOGY 



former letter is now used to designate flagellar antigens, while 

 the latter is applied to the somatic ones. 



The extensive studies of Andrewes (1922, 1925) and of White 

 (1926) have thrown a great deal of light upon the complex anti- 

 genic pattern of the Salmonella group. According to White, E. 

 t]/p]iosa is related to ;S^. eiiteritidis tlirough a common somatic or 

 () antigen. 



Apparently the H antigens of E. typhosa, S. ixiratjjphi A, 

 and S. e7iteyritidis are type specific, while the H antigen of S. 

 paratyphi B, S. aertrycke and a few others are diphasic and 

 may occur in one of two forms. They may change from one H 

 form to another H form. The somatic antigens remain unaltered. 

 The latter, however, as in the case of >S'. cnteritidis, E. typhosa, S. 

 pullorum and *S'. sanguinarium, may be shared by a number of 

 organisms. 



This somatic antigenic relationship between E. tjijjhosa and S. 

 enteritidis must be kept in mind in interpreting a Widal designed 

 to test for fine-flocculating agglutinins. 



The H antigen is contained in cultures showing motility. To 

 prepare antigens, advantage is taken of the solubility of the H 

 antigens in alcohol. Bien and Gardner suggest adding an equal 

 volume of alcohol to thick suspensions of the motile organisms 

 and incubating the suspension at 37° C. for 24 to 36 hours. The 

 alcohol destroys the H antigen. They are not injured, however, by 

 formaldehyde. 



In Chapter VI a description of ''Vi" antigens discovered by 

 Felix and Pitt is given. This is a labile surface antigen that is 

 present in varying amounts in living virulent typhoid bacteria and 

 tends to interfere with agglutination. It is thought to be respon- 

 sible for inagglutinable strains of virulent E. typhosa. 



Variations in Ag"g"lutination Titer Following Vaccination. — In- 

 formation relative to the variation of agglutinin titer following 

 vaccination has been obtained by studying the antibody response in 

 the lower animals and in man following vaccination. Jorgensen 

 and Madsen (1902), Levin (1902), Staubli (1903) and others very 

 early in this century made notable contributions along these lines. 



More recently Felix (1924), Stuart and Krikorian (1928-29), 

 and Dulaney, Wikle, Stewart, Rayfield, et al. (1933), have in- 

 vestigated the relative agglutinin response following vaccination 



