When the disturbance is profound enough to produce a definite, recognizable condition, it is designated as a deficiency disease, of which there are three: scurvy, beri-beri and xerophthalmia. With these are sometimes included rickets and pellagra. The exact cause of the two latter disorders is not definitely known but both are associated with faulty nutrition. Poor hygienic conditions may enter into the causation of rickets, and infection may be a factor in the occurrence of pellagra, but neither disease appears in people who are suitably fed while both diseases may be produced by faulty diet and both may be cured with suitable food. But probably of graver importance to the public welfare than the well defined nutritional disturbances, themselves, is the fact that between a state of good health and the level upon which a disease is recognizable is a long scale, along which is ranged an uncounted army of under-par, half-sick people. These are the ones who are tired, nervous, susceptible to infections, with feeble recuperative powers, and in general are more or less ineffective in the business of life. It is this borderline state, or as Dr. Goldberger terms it, “the twilight zone,” which cannot quite be called disease but is not health, that is serious to the masses, for diagnosed disease is given treatment, but nervousness, lack of energy and endurance, weakness and inefficiency are not treated; as a rule they are merely tolerated. The sufferers fail to reach their highest possible development and they fail to be of highest value to society. This is the condition which can be so largely prevented by giving the baby a good nutritional foundation. This must be started during his prenatal existence, carried through the nursing period and then continued throughout the rest of his life. It will mean much to the coming generation if the expectant and nursing mothers at large are able so to compose their diets that they will provide not only the requisite fats, proteins, carbohydrates, minerals and water and yield the necessary calories, but will contain, also, all three protective substances: fat-soluble A, water-soluble B and water-soluble C. It can be demonstrated that when these food factors are not present in the mother’s diet, they will not appear in her milk, and accordingly will not be supplied to her baby. That is the crux of the whole question. If your diet is faulty, your milk will be faulty in the same respect and your baby, being incompletely nourished, will start life with tissues that are lacking in those substances that are needed to make them sound and to promote health. That is what we have in mind when we say that the mother’s milk must be satisfactory not alone in quantity but in quality as well, if the baby is to be well nourished.