1. With the production of corresponding organ antibody, the complement titer generally showed slight decline on the immunization of normal rabit by heterologous oragan antiserum, i. e. the various organs of normal canine, liver, Kidney, spleen, stomach, duodenum, gallbladder and colon. The rise of the antibody titer matching to various organs, corresponding with the period of decline of decline of complement titer, was found since the observation of relation between the complement titer and corresponding organ antibody on the administration of antiserum obtained by the immunization to normal canine. 2, The decline of complement titer was observed on the cases with the administration of antiserum of the organ which was recognized to have no direct connection with the production of complement, since observing the Vicissitude of complement titer on the cases with the administration of various heterologous organ antiserum in the same manner. 3. The decline of complement titer was observed on the intraperitoneal administration of organ antigen and organ antiserum to guinea pig at the same time, and the action of complement combinative antigen antibody reaction was confirmed in vivo. 4. The decline of complement titer was observed on the normal rabit with the liver exclusion. 5. The decline of complement titer and the change of hemogram were observed on the administration of homologus anti-liver-rabit's serum previously produced to normal rabit, like their change on the administration of heterologous organ antiserum.