It has been quite satisfactorily settled that the discharge of the ovum from the ovary generally takes place about the time of the cessation of the flow. Immediately after the discharge, the sexual desires of the female are more intense than at other times. This fact is particularly manifest in lower animals. The following remark by Prof. Dalton is especially significant to those who care to appreciate its bearing:-- "It is a remarkable fact, in this connection, that the female of these [domestic] animals will allow the approaches of the male only during and immediately after the oestrual period [rut]; that is, just when the egg is recently discharged, and ready for impregnation. At other times, when sexual intercourse would be necessarily fruitless, the instinct of the animal leads her to avoid it; and the concourse of the sexes is accordingly made to correspond in time with the maturity of the egg and its aptitude for fecundation." The amount of fluid lost during the menstrual flow varies greatly with different individuals. It is estimated at from three ounces to half a pint. In cases of deranged function, it may be much greater than this. It is not all blood, however, a considerable portion being mucus. It is rather difficult to understand why the discharge of so considerable a quantity of blood is required. There is no benefit derived from a very copious discharge, as some suppose. Facts seem to indicate that in general those enjoy the best health who lose but small quantities of blood in this manner. A Critical Period.--As the first occurrence of menstruation is a very critical period in the life of a female, and as each recurrence of the function renders her especially susceptible to morbid influences, and liable to serious derangements, a few hints respecting the proper care of an individual at these periods may be acceptable. Important Hints.--1. Avoid taking cold. To do this, it is necessary to avoid exposure; not that a person must be constantly confined in a warm room, for such a course would be the surest way in which to increase the susceptibility to cold. Nothing will disturb the menstrual process more quickly than a sudden chilling of the body when in a state of perspiration, or after confinement in a warm room, by exposure, without sufficient protection, to cold air. A daily bath and daily exercise in the open air are the best known means of preventing colds.