Most young girls have a return of the discharge after a month, the menses afterwards recurring regularly; some do not become regular until after several months. Sometimes the function is imperfectly performed; such cases are accompanied with considerable distress. In some young girls the precursory symptoms of the first appearance of the menses may not be followed by a flow of blood, and there is an apparent effort of nature recurring monthly for several months before the courses become established. There are occasional examples of retarded menstruation. I am acquainted with one woman who at the age of twenty-five years has not menstruated. The absence of the menses does not render conception impossible, in every case. After the menses are established, until the time of their cessation, they generally return every month, unless interrupted by pregnancy or nursing. The average of the catamenial period is about twenty-eight days; in a large number it is thirty days; in some instances they recur every fifteen days. The duration of the flow varies from one to eight days; three or four days is the most usual duration. The quantity of blood lost is variable; from three to five ounces is said to be the average. When the ovaries are congenitally absent, or have been removed, or have become disorganized, menstruation is absent, or ceases. The cause of the menses is the successive evolution of the Graafian vesicles; but the regular process may go on in the ovary without the regular sanguineous discharge. The menses continue in the majority of cases until about the age of 46 years, or perhaps in this country 48 years. According to Dr. Robertson, of England, the periods at which it closed in 77 individuals was, in 1 at the age of 35 years, 4 at 40, 1 at 42, 1 at 43, 3 at 44, 4 at 45, 3 at 47, 10 at 48, 7 at 49, 26 at 50, 2 at 51, 2 at 52, 2 at 53, 2 at 54, 1 at 57, 2 at 60, and 1 at 70. The average duration of the menstrual function is about 30 years. The cessation of the ovarian function is generally announced several years in advance by irregularities of the menses. Besides the intermissions and irregularities, there are other symptoms; a general and indefinite feeling of uneasiness, pelvic pains, itching at the genital parts, flashes of heat in the face, alterations of chilliness and perspiration, leucorrhœa, etc. These troubles are usually slight, and disappear promptly. The time of life has been called the CRITICAL PERIOD, because there has been an opinion prevalent that peculiar dangers attend it. However, the mortality is not greater between the ages of 45 and 50 years than at any other period of life. Yet it is true that in some instances diseases that had been latent previously, declare themselves at this period. THE FUNCTION OF THE OVARIES. We will now consider the physiological action of the ovaries and its intimate connection with the action of the uterus in menstruation, etc.