The occurrence of substances in bacilli of the Salmonella group, 1 inducing in rabbits the formation of sheep hemolysins, so-called Forssman antibodies, has been described by various authors (4), (5), (6), (7). 2 Such antigens have been found by Seiffert (6) in strains of B. paratyphosus (Schottmüller and Freiburg) and of B. enteritıdis Gaertner, and by Meyer in the types Newport and Berlin. Other bacilli which have been shown to contain Forssman antigens, are B. dysenteriae Shiga (9), (10), a particular strain of B. leptisepticus (11), and pneumococci (12), (13). That the various bacillary antigens are not identical, has been shown by Jungeblut and Ross for B. paratyphosus B and B. dysenteriae Shiga, and Meyer has demonstrated that immune sera containing sheep lysin, produced by four different strains of the Salmonella group (B. paratyphosus B, B Berlin, B Newport, and B. enteridıtis Gaertner) were absorbable only by the homologous organisms (see Eisler (14)).