The ordinary method of the biological direct assay has been described by many authors and most investigators being engaged in the biological assay have practiced the method for a long time. It seems, however, to us that the method is in need of large number of subjects and the fiducial limits appling Fieller\u27s theorem are mostly too wide to be useful for the consideration of the relative potency of test preparation, in spite of that the principle of Fieller\u27s theorem itself contains a kind of discussion. In this paper, an extensive method of the direct assay is proposed and its analysis is shown with the numerical illustrations. Because of that our preferable circumstances assumed in section 2 is satisfied naturally as our situation performing the considerable kinds of biological assay, and the analytical method is devised sufficiently from the theoretical and practical viewpoints, it seems that our extensive direct assay may be advantage to estimate and test the potency of test preparation for some direct assays in aid of the above appeals for the improvement of the customary direct assay
