Milk taken slowly into the stomach usually forms curd in small particles, so is digested thoroughly. Crackers and crumbed bread in milk also prevent the formation of a large clot and thus make milk more digestible. When milk is used as a food-ingredient, this is also effected. The lime salts in milk keep the casein in solution. Lime-water added to milk acts similarly in preventing an indigestible clot's forming in the stomach. Barley-water in milk also does this.

Protein in milk forms the scum when milk is heated. It is the change in the protein in milk that makes boiled milk less digestible (when it is so) than uncooked milk. Hutchinson, the food-scientist, claims that milk heated even to the boiling point for 30 min. is as fully digested by infants as raw milk. Many others say it is less so. But to insure its safety when its source is not securely sanitary, it is heated to destroy all germs possible.. (See pasteurized and certified milk, p. 118).

Fat in milk (cream) is broken up into fine globules. This facilitates its digestion. (Fat particles are visible under the microscope; see them if possible.) Cream and butter are both digestible, indeed the most generally digestible fats. Fat is the constituent that varies most in milk. Four per cent is the average; it ranges from 2 to 6 %. This is sometimes a natural difference due mainly to the difference in feeding cows and the breed. Adulteration may also alter the quantity of cream.

Carbohydrate in milk is in the form of milk-sugar (lactose). This sugar is less sweet and less fermentable than other sugars; it is therefore in less danger of disturbing digestion.

Salts of milk (chiefly potash, lime, phosphates) aid in holding the solids in solution. In the body these salts build bone, besides furthering digestion. In illness involving bone-deterioration these salts act as repair agents.