In concluding this chapter it may be well to epitomize the system of living by means of which we and our descendants may recover the physical prestige we are rapidly losing owing to changed conditions of living, especially with respect to our food habits. The system of diet which can be confidently recommended with assurances that it will go a long way toward improving the physical fitness of the nation is a very simple one, and its daily practice involves no great self-denial. It involves the borrowing of the best elements in those several systems of diet which have been thoroughly tested in human experience and have been found successful.

The first and most important principle is the extension of the use of dairy products. Instead of the present consumption of half a pint of milk a day there should be at least a quart per capita. Somewhat more than this would probably be nearer the optimum. This is the feature of the diet of all the pastoral peoples of the past and present, which made them superior in physical perfection to all other peoples. The second principle to be kept in mind is that there are dietary properties in the leafy vegetables, which are unique among foods of vegetable origin. These have been the "protective foods" for many of the Asiatic peoples. Their consumption in liberal quantities as regular constituents of the diet serves not only to provide the body with valuable nutrients it cannot secure in adequate amounts from milled cereals, tubers and muscle meats, but also serves to maintain the intestinal tract in a hygienic condition through promoting prompt elimination. Milk likewise serves, through its encouragement of the growth of lactic acid-producing organisms (which cause souring of milk), to bring about the disappearance from the intestine of those types of bacteria causing putrefactive decomposition of the food residues with the production of substances which are a physiological abomination. This principle, first enunciated by Metchnikoff, is shown by modern bacteriological studies, to be sound. Milk has, however, dietary properties which the famous bacteriologist did not discern, and which make it the one food for which there is no effective substitute.

It is essential to keep also in mind the third principle of great importance in nutrition, viz., that of taking regularly a certain amount of raw vegetable food for the specific purpose of providing the body with a sufficient amount of the anti-scorbutic substance.

If these simple principles are adhered to, the main features of an adequate diet will be fulfilled, and the remainder of the food supply may safely be derived from any of our ordinary milled cereal products, tubers, root vegetables, meats, etc. It is distinctly to be recommended on physiological grounds, however, that the consumption of meats be kept at a somewhat lower plane than is now the rule.

It would be beyond the scope of the present discussion of nutrition to discuss in an adequate way the details of putting into effect in the home the ideal system of diet. Miss Simmonds and the author have treated this subject adequately elsewhere from the point of view of the housewife (9). It must suffice here to say that aside from the liberal use of milk in the many ways in which it can enter into the diet without in any way disturbing our established food habits, the desired end is to be attained through the daily consumption of the vegetables we class as greens or pot-herbs, and through the practice of eating salad dishes twice a day.