The purpose of this book is to present the principles of the chemistry of food and nutrition with special reference to the food requirements of man and the considerations which should underlie our judgment of the nutritive values of foods. Food is here considered chiefly in its relations to nutrition, the more detailed description of individual articles of food and the chemical and legal control of the food industry having been treated in another volume.

The present work is the outgrowth of several years' experience in teaching the subject and is published primarily to meet the needs of college classes. It is hoped that the book may also be of service to other readers who appreciate the importance of food and nutrition as factors in health and are interested in the scientific foundations which have been so greatly broadened and strengthened by the investigations of the past few years.

While the small size, to which the book is limited by its main purpose, permits little of either historical or technically critical treatment, yet a limited number of original investigations and of controverted views have been discussed in order to give an idea of the nature of the evidence on which our present beliefs are based, and in some cases to put the reader on guard against theories which, while now outgrown, are still sometimes encountered.

Special attention has been given to the difficult task of attempting to present the striking results of some of the most recent investigations in nutrition in such a manner as to make clear their importance without giving exaggerated impressions and with due emphasis upon the fact that on many significant points any interpretation which can now be offered is necessarily tentative. It is hoped that study of the text will be supplemented by consultation of the references suggested at the close of each chapter, which should serve to put the reader in touch with much of the more significant literature and make him familiar with the scientific journals in which the future developments of this rapidly growing subject may be followed as they appear.

The author desires to express his indebtedness to the colleagues and former students who have contributed many helpful suggestions and specifically to Doctors A. W. Thomas and M. S. Rose, Miss L. H. Gillett and Miss H. M. Pope for valuable criticism and assistance in the preparation of the present revision of the work.

H. C. S.

November, 1917.