~Amount and Type of Alkali Used.~--The amount of alkali[70] necessary to bring about any change in the general effect of the formula must be determined by the amount of milk and cream in the mixture, since these constituents alone determine the acid content. However, it is impossible to judge exactly the amount of alkali to add, but an approximate estimate is made from the work done by the various investigators. It has been estimated that from 25 to 50% of limewater must be added to milk to change it to any marked degree. In using bicarbonate of soda, a much less quantity brings about the desired result, 1-1/2 grains of bicarbonate of soda being equal to one ounce of limewater. The action of these two alkalies is different. The soda acting upon the milk causes the curds to be more porous, and therefore more easily acted upon in digestion. Sodium citrate likewise tends to prevent the formation of tough curds. It is added in amounts of 1 to 2 grains to each ounce of milk or cream in the mixture whenever it is found necessary to use it at all. The addition of any alkali to the formula is resorted to if the symptoms indicate the need for it, but the type and quantity is entirely within the province of the physician, not the nurse. ~The Addition of Sugar.~--~Lactose~ is the form in which the carbohydrates are found in milk, and it has been a general rule to employ this sugar in making up the sugar content of a formula, using from 6 to 7% of the mixture in this form to cover the necessary energy requirements of the infant. Other sugars are used, however; and of late years malt sugar has been widely employed for this purpose. The form now generally accepted is known as ~dextri-maltose~, which is a combination of dextrin and maltose, both of which are readily acted upon by the sugar-splitting enzymes of the digestive juices. In digestion, lactose or milk sugar is split to dextrose and galactose and utilized in the body, both as a source of energy and as a food for the lactic acid bacteria which are active in the small intestine. ~Malted Foods.~--The addition of malted foods or malt sugar to the food of infants tends to bring about a more rapid gain, both in energy and in body weight, than is generally the case where other sugars are used. This sugar is used as a substitute for milk sugar in many formulas, especially in those cases in which the casein of cow's milk needs to be made more digestible in form. Malt sugar is indicated in the following conditions:[71] (1) in severe atrophies, (2) in cases of fat indigestion before the atrophic stage is reached, (3) in cases where there is slight curd indigestion, indicated by some vomiting and slow gain in weight, (4) in cases where excessive intestinal fermentation is manifested by gas and colic. ~Malt sugar~ (dextri-maltose) is contraindicated to a slight degree in cases "of simple acute diarrhea where lactose, by supplying fermentative media, more easily restores the normal bacterial balance."