The various tissues of the body and the bony skeleton are built by the proteins and salt. Accordingly Nature supplies these in greater abundance to the baby calf, who grows so fast as to double his birth weight in about forty-seven days, than to the baby boy who scarcely doubles his birth weight within 180 days. The calf begins life with a physical need for the large amount of proteins and salts which are present in cows’ milk and with digestive organs that can cope with them, but the baby needs less, can digest less and, therefore, should be given less. There are of course, other and finer differences between the two milks and an attempt is sometimes make to meet these. For example, mother’s milk is slightly alkaline and cows’ milk slightly acid and the curd of cows’ milk is larger, tougher and harder to digest than that formed by mother’s milk. Some doctors add lime water to cows’ milk, before giving it to the baby, to make it alkaline and have the curd made softer, finer and more digestible by boiling. =Articles Needed in Preparing the Baby’s Food.= A complete equipment for preparing and giving the baby’s milk should be assembled, kept in a clean place, separate from utensils in general use, and never put to any other service. A satisfactory outfit for this purpose comprises the following articles: One dozen graduated nursing bottles. One dozen nipples. Clean, new corks or a package of sterile, non-absorbent cotton for stoppers. Bottle brush. Covered kettle, capacity one gallon, for boiling bottles and possibly pasteurizing milk. Pasteurizer or wire bottle rack. Small kettle, about one quart size. Graduated pint or quart measuring glass. Pitcher, two-quart size. Long-handled spoon for mixing. Funnel. Measuring spoons—table and tea sizes. Double boiler. Thermometer which will register at least 212° F. Cream dipper (if ordered). Two small covered jars for sterile and used nipples. Sugar (lactose, maltose or cane sugar according to orders). Lime water (if ordered). Utensils of enamel or aluminum ware are probably the most satisfactory ones to use as they are easily kept clean, while bottles with wide mouths and curved bottoms and inner surfaces can be thoroughly washed more easily than those with small necks and sharp corners. Nipples that can be turned inside out to be washed should be selected as it is almost impossible to clean thoroughly those with tubes or narrow necks. New bottles will be rendered less breakable if placed in cold water, which is gradually heated, allowed to boil for half an hour and cooled before the bottles are removed.