Wagner-Jauregg was led to adopt the treatment of general paralysis by malaria, following the preliminary observations he had made in 1887. He and many other investigators had noticed the tendency of paretics to improve after intercurrent affections, and he finally decided to use benign tertian malaria because he had satisfied himself that it could be controlled whenever desired. The publication of his results and those of Gerstmann, Weygandt, Kirschbaum, Delgado and others attracted considerable attention, and an increasing amount of literature on the subject is accumulating. Observations on this subject are being made in most European countries, in America and in this country. So far the treatment has been empirical; no one has been able to prove why infection with malaria should produce such striking results. Jahnel and Weichbrodt have shown the destructive influence of high temperature as such on the spirochætes, and it may be the case that the intermittent waves of high temperature may be more destructive to the spirochætes than a continuous temperature to which the organisms might have a better chance to adjust. Again it may be that spirochætes under these conditions would be more readily killed when arsenic is given. Muelilens and Kirschbaum hold the view that there is a great impoverishment of the blood following inoculation, and that the subsequent regeneration leads to a reactivation of the immunity process. In this connection it may be noted that some authorities, e.g., Brown and Pearce, believe that success in the treatment of neuro-syphilis by chemical preparations, e.g., tryparsamide, is due, not to the germicidal properties of the chemicals in question, but to the fact that these chemicals confer some form of protective reaction on the tissue cells which enables them to exercise a destructive effect on the spirochætes. Moore has pointed out that the relative infrequency of clinical neuro-syphilis in women as compared with men may be due to the incidence of pregnancy. It is known that pregnancy modifies the reaction to syphilitic infection, and it may be that the physiological process in pregnancy tends to prevent the disease.