Of course, it will be necessary in preparing the supplementary feeding to take the same precautions as if the infant were on the bottle exclusively. To avoid contamination of the milk care must be exercised to have everything perfectly clean that comes in contact with it. And it will be necessary also to vary from time to time both the strength and the amount of the feeding. These alterations will be made most successfully if left to the judgment of a physician who is familiar with the development of the infant and who may be guided accordingly. WEANING.--Occasionally, even before they are delivered, women express the conviction that they will be incapable of nursing. A few mothers who take this attitude, which it would seem is becoming more and more common, make no attempt at nursing, and others give it up after a very short trial. Premature weaning is practiced among the women of two widely different classes: those who are unwilling to deny themselves social pleasures, and those who, because they must earn a living, cannot be encumbered with maternal duties. A still larger class, however, are those mothers who wean the baby for neither of these reasons, but rather because they become discouraged and conclude that there is something wrong with their milk. In this way many infants are weaned without sufficient reason. Before giving up nursing her child a mother should submit several samples of the milk for analysis. If it is unfit for the infant, reliable evidence of the fact will often be secured in this way. With the exception of tuberculosis, physicians recognize no condition that necessarily unfits a mother for nursing. As we have already seen, pregnancy is generally incompatible with lactation; in the event of conception the mother's milk almost always takes on qualities which render it unsatisfactory for the infant, and yet occasionally pregnancy advances several months before these changes in the milk occur. Meanwhile the infant suffers no inconvenience, and often in these cases the symptoms of threatened miscarriage give the first intimation of the mother's condition. Under all circumstances, however, nursing should cease as soon as the mother recognizes that she is pregnant, for probably no woman is strong enough to provide nourishment for her infant and for the development of the embryo simultaneously. Menstruation, on the other hand, rarely if ever provides a good and sufficient reason for weaning. In the great majority of instances this function is re-established before lactation ends. There may be a reduction in the amount of milk during menstruation, but if the infant has been given the breast as usual, the supply increases as soon as the period ends. Qualitative disturbances which would render the milk unfit for use are practically never a consequence of menstruation.