The best food for an infant, under ordinary circumstances, is the milk of its mother. The best substitute for the mother is a wet-nurse. Woman's milk ought not to be dispensed with when there is the slightest opportunity to obtain it, particularly when the family history is not good and nutritive disorders are known to exist, or to have existed, in any of its members. When it cannot be had, artificial food must take its place, and it is in the selection of it where most mistakes are constantly made. This much is certain, that without animal's milk no infant can or ought to be brought up; as ass's milk can be had only exceptionally, and dog's milk, which has been said to cure rachitis, is still less available, the milk of either goat or cow must be utilized. The former ought not to be selected if the latter is within reach, mainly for the reason that it contains, besides other objectionable features which it possesses in common with cow's milk, an enormous percentage of fat. Cow's milk differs in this from woman's milk, that it contains more fat, more casein, more potassium, and less sugar than the latter, and that its very casein is not only different in quantity, but also in chemical properties. Even the reaction of the two milks is not the same, woman's milk being always alkaline, cow's milk often either neutral or amphoteric, and liable to acidulate within a short time. Thus, the dilution of cow's milk with water alone yields no equivalent at all of woman's milk, though the dilution be large enough to reduce the amount of casein in the mixture to the requisite percentage of one, and one only, in a hundred. The addition of sugar (loaf-sugar) and of table-salt, and sometimes alkali (bicarbonate of sodium or lime-water, according to special circumstances), is the least that can be insisted upon. Besides, the cow's milk must be boiled to prevent its turning sour too rapidly, and this process may be repeated to advantage several times in the course of the day. Instead of water, some glutinous substance must be used for the purpose of diluting cow's milk. As its casein coagulates in hard, bulky curds, while woman's milk coagulates in small and soft flakes, some substance ought to be selected which keeps its casein in suspension and prevents it from curdling in firm and large masses. Such substances are gum-arabic, gelatin, and the farinacea. Of the latter, all such must be avoided which contain a large percentage of amylum. The younger the baby, the less is it in a fit condition to digest starch; thus arrowroot, rice, and potatoes ought to be shunned. The very best of all farinacea to be used in diluting cow's milk are barley and oatmeal. A thin decoction of either contains a great deal of both nutritious and glutinous elements, the former to be employed under ordinary circumstances, the latter to take its place where there is, on the part of the baby, an unusual tendency to constipation. The decoction may be made of from one to