SUMMARY1. Fresh sperm and DNP of spermic source from long‐standing schizophrenic patients were injected intravenously into rabbits to prepare anti‐serum. Intracutaneous reaction, precipitation reaction, and complement fixation reaction were performed with the said serum on mental patients and normal subject.2. In case of intracutaneous reaction, local rubor became the most extensive after 8–16 hours of injection. A reaction took place in schizophrenic patients especially potently. In anti‐serum cases against fresh sperm, significant differences were observed between reactions in schizophrenic group and normal group. In anti‐serum cases against spermic DNP there were also perceived significant differences between reactions in schizophrenic group and manic‐depressive psychosis, general paresis, psychoneurosis, toxic psychosis as well as normal group.3. There were observable no remarkable differences between sexes in cases of intracutaneous reaction.4. Precipitation reaction was performed between anti‐serum and both sperma exsudate and serum of schizophrenics, manic‐depressive psychosis and normal subject. There was hardly any difference between schizophrenia and manic‐depressive psychosis, but schizophrenia and manic‐depressives showed a little stronger reaction than the normal subject. Neither, it reacted with any serum.5. Complement fixation reactions were made between anti‐serum and both sperma exsudate and serum of schizophrenics, manic‐depressive psychosis and normal subject. As the result, anti‐serum reacted strongly with every sperma exsudates, though there were obtained no findings specific to schizophrenia. Also, there the reaction failed to occur between anti‐s