Abstract
Over 500 immature rats were used in expts. to compare the results of 5-day injections of varying doses of acid extracts made from sheep anterior pituitary glands (S.A.P.E.) and blood of pregnant women (P.B.E.). P.B.E. stimulated greater increase in uterine weights than S.A.P.E. at all doses. At comparable "luteinization" doses S.A.P.E. produced greater increase in ovarian weight than P.B.E. Histological ovarian pictures produced by the 2 extracts differed: S.A.P.E. produced many corpora lutea and many atretic follicles; P.B.E. produced corpora lutea, lutein cysts, graafian follicles, and few atretic follicles. These differences suggest that the ovary-stimulating hormone in the blood of pregnant women is not identical with that occurring in the anterior hypophysis of sheep.