The Allen-Doisy vaginal cornification test is used almost exclusively for the biological assay of oestrogenic preparations. In its commonest form, from one to six injections of the test material are given to spayed rats or mice during the course of two or three days, and vaginal smears are taken on the third, fourth, and perhaps the sixth day. These smears are assessed according to their cellular composition, the simplest method of scoring being to record those with cornified or nucleated epithelial cells but no leucocytes as positive, and the rest as negative. Other methods are in frequent use, in which the various stages of the oestrous cycle are recorded and given key letters, or in which each smear is given a numerical value according to the degree of cornification, &c., observed. The main drawback to most of these more involved ways of assessing the smears is that the results cannot