The Biologic Characteristics of the Normal Vagina

Summary 1. Extensive studies were made on the vaginal tract of more than 500 patients; included in this number were 37 normal patients in whom the studies were made three times weekly through one to three menstrual cycles. The special studies made included determinations of the pH of the vaginal mucosa, cytologic studies of vaginal. smears, examination of smears stained for glycogen content, determination of the bacterial flora, and the study of vaginal biopsies. 2. The role of the estrogens as the major factor in controlling the histologic and cytologic features of the vaginal epithelium is reviewed, but evidence indicating that progesterone and perhaps other steroid hormones have an important influence is presented. Certain cyclic histologic changes were frequently noted on the biopsies, but in the main these were not nearly so clear-cat as the changes noted from cytologic study of vaginal smears. 3. Present evidence indicates that the estrogens are the dominant factor in causing the mobilization of glycogen in the vaginal epithelium; progesterone may aid in this process. Androgens appear to be an inhibiting factor in glyconeogenesis. Glycogen is abundantly present in vaginal biopsies. A concentration of 2.5 to 3.0 mg. per cent was encountered in the upper part of the vagina and smaller concentrations in the lower part of the vagina. The metabolism of vaginal glycogen is not known, but various theories are discussed. Vaginal biopsies prepared with Best's carmine stain were found to be highly suitable for demonstrating distribution of vaginal mucosa. Cyclic changes in glycogen content were far more easily noted in vaginal smears stained by an iodine method. It was found that the glycogen content of the superficial vaginal epithelium showed a tendency to increase throughout the cycle and then to fall in the late premenstrual phase, thus roughly approximating the estrogen excretion through the cycle. 4. The various methods for determining the pH of the vaginal secretion and mucosa are reviewed. Direct determination of the pH of the vaginal mucosa by the glass electrode method was chosen as most accurate and reliable. A special glass electrode is described which has been found to be highly satisfactory for this purpose. In making 632 readings on 100 normal women, it was found that the pH varied from 4.0 to 5.0 in all except 3 per cent of the determinations. A pH gradient was found to exist in the vagina in most patients. The highest acidity was generally encountered in the anterior fornix. The next highest readings were obtained in the middle third of the vagina; these were generally quite constant and most nearly approximated the pH of the vaginal secretion. Lower values were obtained in the lower third of the vagina, while determinations made in the posterior fornix usually varied considerably. In the 37 cases studied at frequent intervals, a periodic variation in pH was observed in many instances. The average readings indicate that pH gradually falls to reach its lowest point at the midcycle and then gradually rises to meet the highest values at the premenstrual stage. 5. The factors which influence the character of the vaginal flora are discussed. From available evidence it would appear that the vaginal pH is the strongest immediate factor determining the type of organisms present in the vaginal tract. The vaginal pH and flora were correlated for a large series of patients and indicated that most of the patients with Grade I flora had a vaginal pH of 3.9 to 5.0 (range 3.9 to 6.0, average 4.56). Majority of patients with a Grade II flora-fell in the pH interval 4.6 to 5.5 (range 4.0 to 7.0, average 5.09). In Grade III type the majority of the patients had a pH of 5.1 to 6.0 (range 4.0 to 9.0, average 5.54).