Reactions of immature monkeys (Macacus rhesus) to injections of ovarian hormone

Series of injections of ovarian hormone have been made into normal and ovariectomized immature animals. Injections were made twice daily for twenty‐two days. The total dose exceeded 1000 rat units per animal. Effects noted in the living animals were the appearance of reddening and swelling of the ‘sexual skin’ and change of the cell content of the vaginal smear to the interval type of the mature animal. Measurements made at operation, before and after injections, indicated considerable enlargement of both the cervix and body of the uterus. The thymus glands of the injected animals weighed significantly less than those of the controls. Histologic study of the genital tract showed extreme thickening of the vaginal walls, considerable growth of the uterine epithelium and glands, hypertrophy of the muscle layers of the uterus, and advanced differentiation of the epithelium of the uterine tubes. The ovaries of the injected normal animal were smaller and contained fewer primordial and medium‐sized follicles than those of the controls. The presence of large numbers of atretic follicles, especially large flattened scars from former relatively well‐developed follicles also suggests a harmful effect of this amount of ovarian hormone upon follicular development. Several stages of elimination of ova from polyovular follicles were also observed. There was marked growth in the ducts and an increase in the number of alveoli of the mammary glands.