Methods: To assess the perimenopausal state of 11-month-old mice, estrous cycles of natural ageing mice were comprehended through observing cast-off cells of the vagina.

• 方法：通过观察阴道脱落细胞了解11月龄自然衰老小鼠的动情周期情况，判定11月龄小鼠进入围绝经期；