The menstrual flow is much later in appearing in some families than in others, so that this may be considered as a family idiosyncrasy; and if the girl's health is good, it need cause no anxiety. If, on the contrary, the girl has severe headaches, or suffers in any way, the physician should be summoned at once, as the absence of menstruation may be indicative of some serious pathologic condition, A scanty flow is often indicative of thinness of the blood; on the other hand, serious anemias often lead to profuse menorrhagias or metrorrhagias, as has already been stated. The cause of the profound anemia itself may be insufficient nutrition, overwork, or lack of exercise. Scanty menstruation is often seen to occur in fevers, in the later stages of consumption, in advanced Bright's disease, in malaria, or in any other very serious disease. In these cases it seems to be a conservative process on the part of nature in the run-down state of the system. As consumption progresses menstruation generally ceases absolutely, never to return again; and in this case nothing should be done to try to induce a return of the flow. Great shock sometimes causes a sudden cessation of the flow; and sometimes a sea-voyage, followed by the change of habitat, will cause an obstinate form of amenorrhea. But it cannot be too well understood that, after the menstrual flow has been regularly established, it continues with the greatest regularity throughout the child-bearing period, unless the exposure to wet or cold has been sufficiently severe to cause great indisposition on the part of the woman. In this case it is possible that, if the exposure took place just previous to the time of the expected flow, one period may remain out. But except in case of serious illness,-- as for example, typhoid fever,-- two or more periods do not fail to appear except in the case of pregnancy. Leucorrhea.-- Leuchorrhea, or "whites," is a mucous or mucopurulent discharge from the vagina; it may be a symptom of uterine or vaginal disease. Immediately after the menstrual flow there is a well-marked vaginal secretion which is whitish in appearance; it may be transparent or of a milky color, and is sometimes very acrid. This secretion may also precede the flow, and there is nothing abnormal in this. But any discharge occurring between the periods sufficient to stain the clothing-- the so-called whites or leucorrhea-- is abnormal, and is caused by an inflammation of the vagina or the neighboring parts. In addition to the discharge there is heat and swelling of the parts, more or less local distress, and generally intense nervousness. If the disease is not cured, it may become chronic. The pain, heat, and scalding disappear, but a copious discharge continues, and in this stage the disease may be very obstinate and greatly reduces the strength. The constant drain breaks down the system, producing pallor, debility, pain in the back, palpitation, indigestion, and so forth.