After the discharge has become established it recurs periodically while in health; and its recurrence is so regular, that it can be calculated with great exactness. The usual period of its visitations is from twenty-seven to thirty days. As to the time of its continuance, this is various in different women; but it seldom continues longer than six days, or less than three, and does not cease suddenly, but in a gradual manner. Its approach is generally preceded by certain feelings of oppression or deviation from the ordinary state of health, which warn the individual of what is to happen. There is, in particular, a sensation of fulness about the lower part of the belly, and a relaxation about the uterine system which can scarcely be overlooked by the most heedless. The appetite becomes delicate, the limbs tremble and feel weak, the face becomes pale, and there is a peculiar dark streak or shade under the eyes; sometimes great restlessness, slight fever, headache, heavy and dull pain in the small of the back and bottom of the belly, swelled and hardened breasts, &c. All of which are sometimes instantly relieved by a trifling discharge from the vagina, and this not necessarily colored. It must at the same time be admitted, that in some few constitutions these feelings are so inconsiderable as to be little attended to; so that the woman mixes in society as usual without any apparent inconvenience. The period at which the menses make their appearance, is various; it is much influenced by constitution, climate and mode of life. As a general rule, it takes place at puberty, or at that period at which the female is capable of propagating her species; and this period varies as climate may differ. They constantly, however, keep pace with the development of the body; where this is rapid, they will appear proportionably earlier; where this process is slower, they will appear later: but whenever the menses appear as regular evacuations, they mark the period of puberty: thus, in hot countries, women commence to menstruate at eight or nine years of age, and are not unfrequently mothers at ten.[1]