The streaks indicate the situation of small breaks in the deeper layer of the skin, which is less elastic than the upper layer. They are not painful, and should never cause anxiety. Their size and number vary with the degree of abdominal distention, which in turn depends upon various factors, such as the size of the child and the quantity of amniotic fluid. Although these streaks are most frequently located upon the lower part of the abdomen, they may extend to the outer sides of the thighs; and occasionally appear over the breasts, since they too enlarge during pregnancy. Stretching of the skin, of course, is not confined to pregnancy; consequently, the same kind of streaks often appear in people who are growing stout. Attempts to prevent or limit the pregnancy streaks prove futile. There is a common belief that they may be prevented by the use of vaselin, goose-grease, mutton-fat, or some one of a variety of lotions; but this teaching is not borne out by experience. None of these applications, however, are harmful, and there can be no objection to using them except that they cause needless soiling of the clothing. After the child is born the streaks fade of their own accord, though they rarely disappear entirely. In certain localities the skin grows darker during pregnancy. We have already referred to the deepening of the color around the nipple as one of the signs of pregnancy; a similar but much less pronounced discoloration occurs about the navel, which also becomes shallow and may begin to pout in the latter months of pregnancy. About this time, with very few exceptions, there appears a more or less intense brown line which runs downward from the navel in the middle of the abdomen. Sometimes, though not very often, small dark areas, which have been called "liver spots," appear elsewhere over the body. The name is unfortunate, for the spots do not indicate a disorder of the liver. At present it is generally admitted that alterations in the color of the skin during pregnancy are due to deposits of iron. This mineral substance, among others, as we have learned, is required for the development of the embryo. The child is born with a supply of iron calculated to meet its needs for about a year. Such a reserve is necessary, as Bunge has pointed out, because human milk does not contain enough iron to satisfy the infant's requirements. During pregnancy, therefore, the mother's blood transports iron to the placenta, where it can be absorbed into the child's system; and while being thus transported some of it is deposited in the maternal tissues. The deposits are especially frequent, as I have mentioned, in the middle line of the abdomen, on account of the arrangement of the blood vessels there. Deposits elsewhere may depend upon other conditions; but whatever their cause the pigmentation vanishes a short time after the birth.