This section is from the book "Practical Cooking And Serving", by Janet McKenzie Hill. Also available from Amazon: Practical Cooking and Serving: A Complete Manual of How to Select, Prepare, and Serve Food .
Chemical Composition Of Whole Milk (Atwater)
Water 87.3, protein 3.3, fat 4.0, carbohydrates .5, ash .7, calories 325.
Milk, though classed as a beverage, is in reality a food; and when it is used as a part of a meal the quantity of food ingested should be diminished accordingly. Milk is a perfect food for the young of all milk-giving animals, but on account of the large proportion of water in composition it is not so well adapted to the needs of the adult. Too much liquid would be taken in the effort to secure a proper amount of the needful food elements. Or, in other words, taken alone, milk is not a well-balanced food. The protein is represented by albumen and casein, the carbohydrates by milk sugar. When milk is taken into the stomach, rennin, a digestive ferment found in the gastric juice, coagulates the albumen and casein, thus forming what is called curds. If cow's milk be taken into the stomach, a glassful at a time, these curds will be large and not easily acted upon by the digestive fluids. To remedy this, milk should be "eaten" - that is, swallowed a teaspoonful at a time, or it may be diluted with lime-water, though barley-water is preferable. Lime-water by its alkalinity partly neutralizes the acid of the gastric juice, and thus weakened the curdling process goes on more slowly. But such interference with the natural process of digestion cannot be recommended. Eat the milk, or dilute it with barley-water, or, in the case of adults, sip the milk slowly, eating between the sips bread or some other form of farinaceous food. Adults living on milk have no color, the milk being without iron in composition. Infants have iron stored in the liver that supplies the system for a time.