The Determination of the Median Body‐Weight at which Female Rats reach Maturity.

摘要: Summary. 1 . The same statistical methods which are used in the analysis of biological assays have been applied to certain data for females two species, Rattus norvegicus and R. rattus, order determine body-weights at on average individuals become sexually mature. 2 . In four samples rattus it was found that probits corresponding percentages with corpora lutea their ovaries were linearly related logarithms body weight. This relationship means body-weight individual mature can be regarded as being distributed normally. 3 . From regression line connecting log. an estimate may made weight 50% lutea, together range error attached this estimate. Similarly, from slope standard deviation distribution maturity obtained. Moreover, such lines tested any significant differences either position or slope, so results compared these respects. 4 . one series possible compare values parameters calculated similar estimates derived a small sample 27 had only ovulated once, After allowing fact probably observed some five days after they first ovulated, agreement between estimation satisfactory. 5 . One example is given successful application method male norvegicus. There are, however, difficulties regard criterion adopted defining fecundity more work needs done sex before said generally applicable. 6 . We conclude obtained far shows promise assistance study mammalian reproduction, particularly wild rodents.