DR. CARL G. HARTMANN has recently pub lished* an account of his detailed investigation of menstruation and pregnancy in the monkey, Macacus rhesus. Corner's generalisations concerning the cellular content of the vagina of the monkey are fully corroborated; the leucocyte number falls near the middle of the cycle and the number of cornified cells rises to a peak near the end of the interval. Instead of the vaginal smear method, vaginal lavage has been adopted and has proved more instructive since it enables the cells to be studied in the living condition, vitally stained with methylene blue, which also affords a ready means of differentiating the kinds of cornified cells in the vaginal lumen. The amount of desquamation from the vaginal wall can be quickly read off, after lavage, in terms of the per centage of sediment in the collecting tube. Because of the constancy and reliability of the curve of vaginal desquamation as compared with the character of the cornified cells and leucocytes recovered, the latter are no longer studied and recorded; the amount of desquamation and of uterine bleeding are the two principal factors now studied in menstruating females. When the vagina is practically free of desquamated cells the animal is at a low ebb sexually, and the uterus and ovaries are small and hypo-functional.