_The Functions of the Uterus._—The function of the uterus is to provide a favorable place for the reception of the product of conception, where it may be protected and nourished during the period of its development. The purpose of menstruation is to keep the uterus in suitable condition for the reception of this product of conception at any time. It is now known that the menstrual flow is not the whole of menstruation, and that the changes going on in the uterus are almost as continuous as the process of digestion. _Average Duration of the Menstrual Flow._—The average duration of the menstrual flow is five days, although the variations are considerable in healthy women. A flow lasting any place from two to six days is perfectly consistent with health, but a flow continuing less than two days or more than six days generally indicates a local or general disease. _Character of the Menstrual Flow._—For the first few hours, or perhaps for the first day, the flow is usually slight in quantity and light in color; on the second and third day the flow reaches its height, and is profuse and dark in color, but it should never be clotted; after this it generally ceases. The amount of the flow varies from 5 to 10 ounces. If less than 5 or 6, or more than 18 napkins, are pretty well saturated through, the amount may be considered abnormal. _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 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 period all _cold_ baths must be strictly prohibited, whether tub-baths or cold sponges. The reason for 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 time of 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 throughout 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 local irritation.