Whenever a soft swelling appears over that portion of the scalp which was foremost during the birth, the curiosity of the family is aroused; but the swelling is harmless and subsides quickly. It originates for the same reason that a finger swells if too tight a ring is worn, which, as everyone knows, is because of interference with the circulation. Just as the swelling of the finger disappears when the constriction is removed, so the swelling of the scalp subsides shortly after the child is born. Usually no trace of it can be found the next day; but even when more persistent it will always vanish after a short time. For the child the most notable result of labor relates to the revolutionary changes in its mode of existence. Up to the time of birth the fetus received nourishment by way of the placenta, but after separation from the mother another source of food must be found. The health of the tissues, perpetually in need of oxygen, requires that the lungs act very promptly. Contact with the air, which is cooler than the previous environment of the child, irritates the nerve-endings in the skin; in response to the sensation thus produced breathing is established automatically. Whenever the temperature stimulus proves insufficient, physicians employ a stronger one, spanking the child until it cries lustily. Crying not only expands the lungs, but also has a favorable influence upon needful alterations in the fetal circulation. The lungs, since they must from this time on provide oxygen for the infant, need to receive more blood than formerly. The vessels leading toward them must be widely opened, and structures which previously diverted the blood-stream to the navel must be closed. The intricate shifting of forces which produces the change cannot be understood without a knowledge of anatomy; it will suffice for us to know that the blood is drawn into the vessels of the lungs with each inspiration. Other changes also occur. On account of some of these, namely, certain alterations in the blood current through the heart, physicians once taught that newly born infants should always be laid upon the right side. Except in very unusual cases, that precaution is now regarded as unnecessary.