The ability of some cultures of Eberthella typhosa to cause the production of an antibody not produced by some other cultures of the same species has been confirmed. With one marked exception it was found that fourteen cultures giving evidence of possessing the antigen responsible for this action retained their characteristics with minor fluctuations during two years of observation. The antigen was not found to be deleteriously acted upon by growing the cultures at room temperature. Killing the cultures with 0.4 per cent formaldehyde or the combined action of 0.5 per cent phenol and 33 per cent alcohol did not affect the agglutinogenic properties of the so-called “Vi” component. However, growing the organisms on agar containing phenol, 1:900, or killing them with heat, merthiolate, or phenol alone changed or destroyed this attribute.
It was found that twenty-four-hour agar cultures were better suited for the demonstration of hypoagglutinability in O antisera than four-hour broth cultures and were just as well suited for agglutination in “Vi” antiserum and reactivity to phage as the latter.
In a comparison of methods for determining the presence of the “Vi” antigen it appeared that sensitivity to the bacteriophage of Craigie, agglutinability by “Vi” antiserum, and the ability of the culture to kill one or more mice in a dose of 100 million organisms were well correlated, but that the phage reaction was most easily demonstrated. Quantitative relationships could not be shown to obtain by the simultaneous use of the methods tested.