23 days after the beginning of the last menstruation in 19 24 days after the beginning of the last menstruation in 29 25 days after the beginning of the last menstruation in 36 26 days after the beginning of the last menstruation in 56 27 days after the beginning of the last menstruation in 62 28 days after the beginning of the last menstruation in 73 ——— 275 === and in the remaining cases at other intervals than those stated. He is, therefore, of opinion that in the majority of Jewish women the type of menstruation is shorter then twenty-nine days. According to _Brierre de Boismont_, among 100 women menstruation recurred: Every 4 weeks in 61 women. Every 3 weeks in 28 women. Every 2 weeks in 1 woman. And at various irregular periods in 10 women. _Tilt_ found among 100 women that menstruation recurred: Every 4 weeks in 77 women. Every 3 weeks in 17 women. Every 2 weeks in 1 woman. Every 6 weeks in 5 women. _Foster_ instituted inquiries regarding this matter in 56 healthy women. In 380 periods, 45 recurred after an interval of 28 days, 225 after a shorter interval than this, 110 after a longer interval. The duration of the flow varied from 1 to 14 days; most commonly it lasted from 3 to 5 days. A peculiar change in the type of menstruation sometimes manifests itself in this way, that in women in whom the regular four-weekly type of menstruation has prevailed, exactly in the middle of this four-weekly period the menstrual molimina, with or without menstrual discharge, make their appearance; the patient suffers from pain in the lower belly, sacrache, sensation of weight, and bearing-down pains. _Courty_, _Dubois_, and _Pajot Négrier_ have described such cases of _molimen utérin intermenstruel_, which _Tilt_ denotes by the term _remittent menstruation_. From the earliest times the process of menstruation has attracted the attention of natural philosophers, and has led them to formulate hypotheses and to institute investigations, especially in order to ascertain whether the connection between ovulation and menstruation is one of temporal succession merely, or whether the relation is a causal one. From _Hippocrates_ and _Galen_ downwards until well beyond the middle ages, the view of the father of medicine was generally accepted, that menstruation is a purificatory process by means of which materials harmful to the organism are eliminated from the body—a view which finds expression also in the religious and legal ordinances of all times.