The Experiments of Chittenden and of Benedict covered but approximately 1 per cent of the expectation of life of the young men who served as subjects. They can scarcely be expected to be used as a basis of deductions of a far-reaching nature concerning the dietary practices which man may safely adhere to throughout long periods. Our conclusions as to what is safe or unsafe must be arrived at through tests of special types of diets on animals, the life histories of which are carefully observed, and the vitality of whose offspring is carefully compared with a satisfactory standard of excellence, and the correlation of these results with the experience of man in various parts of the world, where groups are found whose dietary habits are of peculiar and restricted types. Such data will be set forth in later chapters of this book.