By _leafy vegetables_ we mean lettuce, romaine, endive, cress, celery, cabbage, spinach, onions, string beans, asparagus, cauliflower, Brussels sprouts, artichokes, beet greens, dandelions, turnip tops and the like. Other foods which are rich in protective substances are fresh fruit, egg-yolks and glandular organs. Nearly all of the common foods are deficient in some respect, but as the shortcomings of the various groups are different, we can arrange entirely satisfactory diets by combining foods which supplement each other’s deficiencies. This explains to us why the meat-potato-peas-beans-bread-and-pie type of meals fails to supply adequate nourishment. These foods belong in the same general group and are deficient in about the same kind of food factors, thus tending to duplicate, rather than supplement each other. If such a fare is enriched by the addition of the protective foods, milk and leafy vegetables, we have a well rounded diet in which the deficiencies of one group of foods are supplied by the properties of the other groups. In fact, it is only by such a supplementing combination that an entirely satisfactory diet can be secured. Dr. McCollum points out that the mother on a faulty diet cannot nurse her baby to his advantage. “The mammary gland,” he says, “picks up from the blood both of the chemically unidentified food essentials, fat-soluble A and water-soluble B, and passes these into the milk, but it is unable to produce either of these substances anew. When one or the other of these is absent from the mother’s diet it is not found in the milk. We have shown the possibility of producing milk, poor or lacking in each of these substances and therefore not capable of inducing growth.”[12]