3. The diseases resulting from a lack or deficiency of the protective substances, fat-soluble A, water-soluble B and water-soluble C, respectively, are xerophthalmia, beri-beri and scurvy. With these are often included pellagra and rickets, the causes of which are not definitely known but result from diets that are poor in certain respects. The serious aspect of the deficiency diseases, however, does not lie entirely in those conditions which are well enough developed to be recognizable, thus prompting treatment; but also in the wide prevalence of malnutrition, of some form, which is not severe enough to be diagnosed as disease, and which is caused by a sustained diet that is poor in one or more essential food factors. This condition is serious because it produces a legion of individuals who are spoken of as being “not strong.” They are tired, nervous, susceptible to infections, have poor recuperative powers and in general fall short of a normal state of health and efficiency. 4. Although the breast tissues are capable of converting into milk certain substances which they extract from the blood, and may, for example, convert poor proteins into proteins of higher value, they cannot create the protective substances which we have been considering. They can merely excrete these substances if they are contained in the mother’s diet. The absence, or shortage of these food essentials in the mother’s diet, and therefore in her milk, may result in rickets or other malnourished conditions in the baby, or in a degree of faulty nutrition which is not marked enough to be diagnosed, but enough to keep him frail. Enough to give him the poor start that is so likely to put him, ultimately, in the class of those adults who are more or less unfit, though not actually ill. We must see to it, therefore, that our selection of food for the expectant and nursing mother provides those substances which are necessary to promote growth and development and preserve health, if we are to live up to our claim that the aim of obstetrical nursing is to aid in building a strong, vigorous and buoyant race. The nurse may find herself feeling a bit dismayed at the prospect of trying to remember at all times which foods contain fat-soluble A, for example, and which are poor in water-soluble C, but she can remember in general, that milk and leafy vegetables are the great protective foods and that any diet which is poor in these is incapable of nourishing satisfactorily; and by calling to mind the deficiency diseases, previously described, she will be impressed anew by the seriousness of faulty nutrition. By _milk_ we mean, in addition to fresh milk, cream, butter, butter-milk, cream-soups and sauces, custards, ice-cream and all dishes and beverages made of milk.