The follicular hormone occurs in both amniotic and allantoic fluid of cattle in equal amounts. This is the richest source obtainable from slaughter houses. About 200 units per gallon of fetal fluid is obtained. The preparation is water soluble, non-toxic and has the physiological properties of the follicular hormone. It causes estrus in spayed rats, menstruation in ovariectomized monkeys and hastens sexual maturity as evidenced by the opening of the vaginal orifice.