Why, in a given species, puberty sets in at a fairly fixed period of time has always remained a mystery. In recent years various glands of internal secretion have, without real evidence, been credited with a restraining or accelerating influence. Clinical record of premature puberty has accumulated and has shown that pineal, suprarenal or ovarian neoplasms are most often causative, although cases in which no abnormality other than the precocious puberty is discoverable are also not unusual (Lenz;1Reuben and Manning2). Premature puberty can be experimentally induced by the injection of lipoid extracts of corpus luteum, placenta or follicle fluid. Such experiments have been performed since 1913 on rabbits, guinea-pigs and albino rats (Aschner;3Fellner;4Frank and Rosenbloom;5Frank;6Allen and Doisy;7Frank and Gustavson8). The effect shows itself in a marked hyperplasia of the female genital tubular system (vulva, vagina, uterus)