After injected once bovine's serum antigen toward the normal rabbit, and the rabbit with impediments in the reticulo-endothelial function due to ink injection and splenorectomy, I have pro kg 5 γ of Platonin in two groups injections three times every other day and the same amount once a day for the whole week continuously (7 times), and then have taken observations on such matters as Congo-red index, serum protein density especially γ-Globulin, precipitin value, and quantitative changes, and obtained the results as follows'. 1) In case of normal rabbit, the injections three times every other day has shown remarkable effect than that of once a day for the whole week continuously; in case of rabbit with impediments in the reticulo-endothelial function due to splenorect my and ink injection, the latter has indicated more remarkable results than the former. 2) Among every groups, antibody production has proved at its maximum in 14 days after antigen injection, but has gradually showed decrease. When the antibody production has proved at its maximum as quickened by injection of Platonin, it could be seen that the decline in precipitin value and quantitative changes has proved as slowly especially in former compared with others, and antibody in serum has kept for a long time. 3) In this chapter, the precipitin value and quantity has proved at its maximum as quickened in every groups compared with the case of no administration of Platonin as reported at Chapter One, and injection of Platonin has proved to quicken upon the antibody production. 4) Serum protein esp. γ-Globulin showed almost a parallel relation with antibody, while no definite changes could be seen. When the function of reticulo-endothelial system has proved as quickened by administration of Platonin, the quickened state of antibody production has kept for a long time and at a high level. Further, decline of the reticulo-endothelial function due to splenorectomy has equally showed decrease of γ-Globulin. Therefore, it may be roughly conduluded that a close correlation exists among the reticulo endothelial function, serum protein and γ-Globulin.