They are only for healthy infants. Begin always with a weak formula, especially with an infant previously nursed at the breast, with one just weaned and with infants who have poor digestive powers, or whose digestive powers are unknown. Should the first formula tried be too weak the food can be strengthened every three or four days until the right formula is found. If the food is made too strong at first an attack of indigestion is liable to follow.
How shall I increase the strength of the food? This should be done very gradually. Do not advance more than one formula in the given series. It is frequently better to make the increase in half steps. Say when it is from three to four, give three and one-half, and then four.
How rapidly can I increase the quantity of food? This should not be more than one-fourth ounce in each feeding, one to one and one-half to two ounces daily.
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When should the amount of food be increased? An increase may be necessary every few days in the early weeks, but the same formula is often continued for two or three months during the later months.
What signs in the infant demand an increase? The infant is not satisfied, does not gain in weight, but it has good digestion—that is, it does not vomit and has good stools.
When should I not increase the food? So long as the child is satisfied, gains four to six ounces weekly, even when the quantity and strength of the food is considerably below the average.
Should you then increase the food if the child seems somewhat hungry, but still gains from eight to ten ounces weekly? It is not always a safe rule to be guided by the appetite.
How can I know whether to increase the strength or the quantity of the food? In the early weeks it is well first to increase the strength, the next time the quantity of the food, then the strength, then the quantity, etc. The quantity chiefly should be increased after the fourth or fifth month.
Should a slight stomach discomfort or disturbance follow after the food has been strengthened, what shall I do? If the disturbance is marked and continues and the infant does not seem able to accustom itself to the new food, you should go back to the weaker one and the next increase should be smaller.