Definition of Menstruation.-- Menstruation may, then, be defined as the periodic discharge of blood from the uterus, accompanied by the shedding of the epithelium of the body, as well as that of the uterine glands near their orifices. The sanguineous discharge is due partly to the oozing of blood from the surfaces denuded of epithelium, and partly to active congestion. The discharge from the uterus is largely augmented by mucus secreted in increased quantity at this period from the enlarged uterine glands. The tubes take some part in the process of menstruation; their mucous membrane is swollen, the epithelium is shed in places, and they are filled with a thin bloody fiuid, containing blood-corpuscles and cast-off epithelium cells. The menstrual wave continues from puberty to the menopause; it is a nervous phenomenon. Ovulation is a progressive, non-periodic process; it begins before birth and continues till the ovarian tissue is atrophied or worn out. Premonitory Symptoms of the Flow.-- The premonitory symptoms of the monthly flow should not be so marked as to cause the individual any discomfort. The first indication of the return of the period should be the appearance of the flow. There is generally a feeling of abdominal fulness with some lassitude, and sometimes slight headache. The temperature is lower and the pulse is slower than at other times. This lowered tone of the system is an additional reason for increased care against exposure in wet or cold weather. Hygiene of Menstruation.-- During the menstrual periods all cold baths must be strictly prohibited, whether tub-baths or cold sponges. The reason of this is that the application of cold to the surface causes a driving in of the blood from the exterior of the body to the internal organs; and at the menstrual periods there is already a congested condition of the pelvic organs, and it must be remembered that congestion is the first stage of inflammation. Hot or warm sponge-baths may be taken throughout the period; and the vulva should be bathed with warm water twice a day through the entire period of the flow, as this not only removes the clotted blood before it decomposes and becomes the source of irritation, but also removes other irritating matters, and prevents the nervousness that is caused by a local irritation. It is strange how women who are scrupulously neat in all other respects will allow the smegma to collect in and about the vulva; as a matter of fact, for the purpose of cleanliness it is much more necessary that the external genitals should be washed twice a day with soap and water all through life than that the face should be washed that often. Another question which is still sub judice is the necessity for and the frequency with which vaginal douches should be taken; all physicians are agreed that a vaginal douche taken immediately after the menstrual period is beneficial, as it removes all the debris of the flow, which is sometimes very irritating.