_First appearance of menstruation._ _Average age at _Duration of which menstrual menstruation activity._ ceased, in years._ In 5 cases in the 12th year 47.80 35.80 years. In 10 cases in the 13th year 45.89 32.89 years. In 50 cases in the 14th year 44.98 30.98 years. In 34 cases in the 15th year 45.56 30.56 years. In 38 cases in the 16th year 44.13 29.13 years. In 36 cases in the 17th year 43.00 26.00 years. In 49 cases in the 18th year 44.96 26.96 years. In 33 cases in the 19th year 44.79 25.79 years. In 38 cases in the 20th year 45.36 25.36 years. In 10 cases in the 21st year 44.10 23.10 years. In 4 cases in the 22d year 43.50 21.50 years. In 3 cases in the 23d year 44.33 21.33 years. In 4 cases in the 24th year 39.50 15.50 years. Totals: In 412 cases the average age at the menopause was 44.82, and the average duration of menstrual activity was 27.973 years. From the tables of _L. Mayer_, _Krieger_ has instituted a comparison between the duration of menstrual activity in 101 women who began to menstruate early and 180 women who began to menstruate late, finding in the case of the former a mean duration of 33.673 years, and in the case of the latter a mean duration of 27.344 years, showing therefore a sexual life longer on an average by 6.429 years in those in whom puberty was early as compared with those in whom puberty was late. From the tables of _Tilt_, based on the observation of 164 cases, 76 women in whom menstruation appeared early and 88 in whom it appeared late, we learn that among the former the shortest duration of menstrual activity was 18 years, among the latter 12 years; among the former the longest duration was 37 years, among the latter only 33. The majority of those who began to menstruate early continued to menstruate for 28, 31, 32, 33, 34, 35, 36, 38, or 39 years; those who began to menstruate late, for 23, 27, 28, 30, or 31 years. The mean duration of the sexual life in those who began to menstruate early was 33.66 years; in those who began to menstruate late it was 28.28 years. Since the average duration of the menstrual function is given by _Tilt_ as 31.33 years, those who began to menstruate early exceeded this average by 2.33 years, while those who began to menstruate late exhibited a duration of menstrual activity of at least three years less than the average.