The relationship of Vi types E₃ and E₄ ofSalmonella typhi to Vi types E₁ and D₁

Summary and Conclusions

• 1. Vi phage II E₃ gives in the critical test concentration cross reactions with the Types E₁ and D₁; the specific resistance of Type E₃ is complex, and composed of the specific resistances E₁ and D₁.

• 2. Vi phage II E₄ gives in the critical test concentration cross reactions with the types E₃, E₁ and D₁.

• 3. Type E₄ differs from Type E₃ in phage reactions in that it is more sensitive to preparations of Vi phage II with the specific affinity E₁ and more resistant to preparations of Vi phage II with the specific affinities (E₁) and (D₁).

• 4. It is more difficult to adapt Vi phage II to Type E₄ than to Type E₃, not only if one starts from Vi phage II A (Desranleau, 1947) but also if one starts from Vi phage II D₁.