~Breast Milk versus Cow's Milk.~--Consensus of opinion shows that breast-fed infants require less energy than the ones who must be nourished artificially. This is probably due largely to the fact that the constituents of human milk are in a more available form than those in cow's milk, the former requiring a lesser expenditure of energy on the part of the organism to become available than the latter. Very active babies, ones who kick and throw themselves about or cry violently, have a greater energy requirement than the more placid baby who sleeps more and is more quiet in movement and who cries less when awake. Breast-fed babies are generally more quiet than their less fortunate artificially fed brothers. It has been demonstrated that the artificially fed baby has a much harder fight for existence than the baby who receives his natural food; hence the necessity of using every available means to make the food digestible, and to lessen the danger arising from the additional work put upon the entire apparatus. Cow's milk contains practically the same chemical elements as are found in human milk, but these elements are combined in a slightly different manner, and are not so easily handled by the immature organs. The proteins of milk consist of casein, which is insoluble, and albumen, which is soluble. According to Van Slyke the proportion of insoluble to soluble protein in cow's milk is 3.6:1, while in human milk the proportion is only 1:1. The ash constituents in cow's milk are in excess of the needs of the infant organism, but since a great part of these salts is in an inorganic form they are not retained to the same extent as those contained in human milk, which are in an organic form. ~Rules and Regulations.~--It is not possible to lay down hard and fast laws to cover the subject of infant feeding. The food must be adapted to the individual needs of the baby in question. The nurse must see that the milk is obtained from a responsible dealer, certified milk being of course the safest. The bottles of milk should be wiped off carefully and placed directly on the ice as soon as they are received. The milk generally used in infant feeding has a fat content of 4%. That having a higher percentage of fat is technically cream. The following table showing the fat, sugar, and protein composition of whole milk, cream, skimmed milk, and whey was arranged by Morse and Talbot:[67] TABLE