STUDIES ON THE PHYSIOLOGY OF LACTATION. III. THE RECIPROCAL HYPOPHYSEAL-OVARIAN RELATIONSHIP AS A FACTOR IN THE CONTROL OF LACTATION†§

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Abstract
Nine pregnant guinea-pigs injected with anterior lobe extract (ALE) aborted and lactated. Of 25 females ovariectomized during pregnancy, 9 went to term. Lactation occurred only after fetal expulsion. Hysterectomy in pregnant females did not cause lactation unless ALE was administered. Hysterectomy and ovariectomy of 5 females did induce lactation. Removal of the ovaries and fertile horn only, in 4 cases of unilateral pregnancy, resulted in lactation. The administration of estrin in parturient females prevented lactation; additional administration of pituitary hormone induced lactation except when the dosage of estrin was greatly increased. Conclusion: estrin induces mammary growth during pregnancy, but inhibits lactation during that period. Large amounts of estrin in pregnant animals seem to inhibit the secretion of the lactation-inducing hormone of the anterior lobe, as well as to act directly on the mammary glands. At parturition estrin decreases, lactation-inducing hormone is secreted, and lactation occurs.