It seems almost impossible to get milk from the cow as clean and free from bacteria as it should be and therefore sterilization and pasteurization are resorted to almost universally. Various substances such as formaldehyd, boric acid, and salicylic acid are used by dealers to preserve the milk. These all have a deleterious effect on the child. Therefore the safety of the child demands that the mother choose a reliable dairy. The milk may be analyzed occasionally to make sure of its purity. [Sidenote: Top-Milk] A very popular milk preparation and one frequently prescribed by physicians is the top-milk method as originated by Dr. Holt. Top-milk is that at the top of milk bottles in which milk has been allowed to stand for five or six hours. The cream at the top contains the most fat. For instance, in a quart of milk that has been permitted to stand, the Upper 4 ounces contain 20 per cent. of fat. ” 6 ” ” 16 ” ” ” ” ” 8 ” ” 12 ” ” ” ” ” 10 ” ” 11 ” ” ” ” ” 12 ” ” 9 ” ” ” ” ” 14 ” ” 8 ” ” ” ” ” 16 ” ” 7 ” ” ” ” ” 20 ” ” 6 ” ” ” ” ” 24 ” ” 5 ” ” ” ” To remove the top-milk, the first ounce is taken out with a spoon and the remainder with a Chapin milk dipper which contains one ounce. The following formula is considered a good top-milk mixture, although it is not supposed to meet the needs of all infants and would therefore have to be modified in some cases and made stronger in others. TOP-MILK MIXTURE Top-milk (upper 8 ounces) 2-1/2 ozs.; Bottom-milk 1 oz.; Limewater 1/2 oz.; Milk-sugar 1 measure (1/2 oz.); Water, sufficient to make 8 ozs. The sugar is dissolved by boiling it in the quantity of water to be used for the mixture. If not perfectly clear, it is strained through cheesecloth. The one thing to be particularly guarded against is overloading the stomach with rich food. On account of the high percentage of fat, digestive disturbances often occur when top-milk is used. Some infants can dispose of an abundance of fat from the beginning and most of them can after six or nine months, but many infants have difficulty in digesting fat. The condition called “fat rickets” may exist, though the child may seem to thrive and increase in weight. Its flesh, however, is not hard and firm as it should be in health. The cream from Guernsey and Jersey cows is usually too rich for infants and therefore the best milk for the baby is that from Holstein or grade cows. The mixed milk from various cows is usually best. The physician can determine from the stools if the fat ratio is too high, in which case it is best to use top-milk lower in percentage of fat, and lengthen the feeding intervals to four hours. * * * * * [Sidenote: Certified Milk]