1. From a comparison of the results with arthritis deformans recorded in tables III, IV, and VI, and with the control cases recorded in table VII, one is justified in concluding that Streptococcus viridans is an infectious agent and excites the production of a complement-fixing substance (fixateur) in the organism in cases of arthritis deformans, and, therefore, Streptococcus viridans is the probable causative agent of the disease in many cases of arthritis deformans. Probably 40 per cent. and more of cases of arthritis deformans should be considered as chronic infective deforming arthritis.
2. Rarely the clinical manifestations of arthritis deformans may be due to gonococcus infection.
3. The serum from one case may react positively to two different organisms, most frequently to Streptococcus viridans and to gonococcus, when the reaction to the former should be considered the indicator of the causative agent, since with the latter infection is often latent in the genito-urinary tract. Incidence of gonococcus infection is high and the clinical manifestations of arthritis deformans are rarely produced by gonococcus infection.