_Retention of the milk in the breasts_ alters its character. The longer it is retained, the weaker and more watery it becomes. An acquaintance with this fact is of practical importance to every mother; for it follows from it, that the milk is richer the oftener it is removed from the breast. Therefore, if the digestion of the child is disordered by the milk being too rich, as sometimes happens, the remedy is to give it the breast less frequently by which not only is less taken, but the quality is also rendered poorer. On the contrary, in those instances in which the child is badly nourished and the milk is insufficient in quantity, it should be applied oftener, and the milk thus rendered richer. The milk which last flows is always the richest. Hence, when two children are nursed, the first is the worse served. INFLUENCE OF PREGNANCY ON THE MILK. Menstruation is ordinarily absent, and pregnancy therefore impossible, during the whole course of nursing, at least during the first nine months. Sometimes, however, mothers become unwell at the expiration of the sixth or seventh month; in rare instances, within the first five or six weeks after confinement. When the monthly sickness makes its appearance without any constitutional or local disturbance, it is not apt to interfere with the welfare of the infant. When, on the contrary, the discharge is profuse, and attended with much pain, it may produce colic, vomiting, and diarrhœa in the nursling. The disturbance in the system of the child ordinarily resulting from pregnancy in the mother is such that, as a rule, it should be at once weaned so soon as it is certain that pregnancy exists. The only exceptions to this rule are those cases in the city, during the hot months, in which it is impossible either to procure a wet-nurse or to take the child to the country to be weaned. In cold weather an infant should certainly be weaned, if it has attained its fifth or sixth month, and the mother has become pregnant. INFLUENCE OF THE MOTHER'S MIND OVER THE NURSING CHILD. We have spoken, in treating of mothers' marks, of the influence of the mother's mind upon her unborn offspring. The influence of the maternal mind does not cease with the birth of the child. The mother continues during the whole period of nursing powerfully to impress, through her milk, the babe at her breast. It is well established, that mental emotions are capable of changing the quantity and quality of the milk, and of thus rendering it hurtful, and even dangerous, to the infant.