1. The relative synergic stimulating influence of anti-horse serum sensitivity, non-hemolytic streptococcal hyperergy and staphylotoxin intoxication have been determined in connection with rabbits' reaction to simultaneous injections of lens extracts. These three synergic states are increasingly active in the order named.
2. Heterologous lens extract is a much more powerful antigen than is homologous lens, even under conditions where the reactivity of the immunized animal has been much enhanced.