Abstract
1. The development in typhus fever blood of agglutinins for a bacillus of the colon-paratyphoid group, which was isolated in 1921 from the faeces of a typhus case is shown to be a frequent occurrence in the disease as met with in Ireland, Poland and Syria. The bacillus has preserved its agglutina-bility up to the time of writing—a period of five years. Owing to its similarity to a bacillus previously isolated by the writer and which was designated bacillus “U,” this bacillus has been named B. agglutinabilis “U2.”2. It has been shown that bacteria preserved in alcohol even for 3 years are sensitive for use in the serological test, and that sera to which equal volumes of pure glycerine have been added retain their agglutinins for atleast 5 years.3. Five strains of B. proteus “X 19” fermented salicin with the production of acid and gas. Ordinary Proteus strains had no action on this glucoside and neither had the anindologenes strain “Kingsbury” although belonging to the “X 19” group.4. Strains of B. proteus “X 19” show great differences in their sensitiveness to typhus fever agglutinins.5. Views which have been advanced to explain the Weil-Felix reaction are discussed and the conclusion is reached that to label it as an instance of paragglutination does not account for the rise and fall of the agglutinins—agglutinins which are formed not only for B. proteus “X2” and “X 19” but for certain strains of the B. pyocyaneus and colon-paratyphoid-typhoid groups.