In the hot climates of Asia, Africa, and America, girls are generally mature at ten years of age, and often at nine; and though the menstrual discharge is less copious in warm countries it is yet more early. The intervals between are nearly the same in every country, and in this respect there seems to be a greater difference between individuals than between nations. In the same climate and nation some women are subject to the menstrua at the end of every fifteenth day, while others are free from them for six weeks; but a month, however, two or three days over or under, is the usual period. The quantity of the discharge seems to depend on the quantity of nourishment, and of insensible perspiration. Women who eat much, and exercise little, have the most copious discharge? in warm countries it is always least, because the perspiration is great. As to its duration, it is generally from three to four or five days, though sometimes to six, seven, and even eight days. The _material_ causes of it are supposed to be a superfluity of blood and nutritive particles. The symptoms which precede are certain indications of repletion; as heat, tension, swelling, and the pains which women feel, not only in the parts themselves, and the adjoining ones, but also in the breasts, which swell and discover a surplus of blood by the _areolæ_, or the circle about the nipple, becoming of a deeper colour. The eyes are oppressed, and underneath their orbits the skin assumes a blue or violet tint; the cheeks are flushed; the head is heavy and full of pain; and the whole body in general is in a state of oppression from the surcharge of blood. At the age of puberty the body usually attains its full growth in length. Just before, young people sometimes increase several inches, but the quickness of growth is most sudden and perceptible in the genitals of both sexes. This growth in males is an expansion merely, but in females it is often attended with a contraction, to which different appellations have been given in explaining the signs of virginity.