Responses of the Stromal Nuclei of the Macaque Endometrium to Estrogen and Progesterone *

The first clear description of the human endometrium in the several phases of the menstrual cycle (Hitschmann and Adler7) embodied the morphological features considered today to be characteristic of each stage of the cycle. These structural entities induded not only differences in the thickness of the endometrium but also heightening of the epithelium and edema, now known to be evoked by estrogenic hormone, and sacculation of the endometrial glands, now known to be dependent upon the presence of progestin. In addition to these conspicuous and universally known characters, Hitschmann and Adler also described and illustrated striking differences in the size and structure of the stromal cells of the endometrium at different stages in the cycle. These cells in the postmenstrual endometrium were described as being small with dense, frequently fusiform, small nuclei. During the growth period these cells enlarge somewhat and their nuclei become less dense and more vesicular. During the premenstrual period they become quite large and resemble young decidual cells. Early in the course of the endocrine analysis of the menstrual cycle in the human being and in the monkey emphasis was placed upon the more conspicuous tissue changes while cytological changes