This book is a popular presentation of a subject which concerns every one of us; for vitamines are substances, as yet ill-defined, whose presence in food is essential to our well-being: their absence makes life impossible. And what more pressing problem to-day than that of food!

The entire subject is not more than ten years old - we ate vitamines before 1910, but we were not aware of it - yet the mass of work that has been done during these few years has added enormously to our knowledge of the science of nutrition. But the results of such research work are securely hidden from the gaze of the layman by their publication in technical journals, and through the use of language which is well-nigh meaningless to the man who is not a food specialist. The aim of the present volume is to reinterpret, in terms of our everyday tongue, the language of the research worker. Though "popular," the book is, I believe, a very faithful account of the labors of our scientific friends.

Experience has taught me that by far the best method of approach to an entirely new subject is the historical or evolutionary. The reasons for each successive step in the process of reasoning and experimentation then become clear. That is why I have devoted the first part of the book to a survey of nutrition prior to the time when vitamines were introduced.

The summary will, I trust, be found to be a convenient brief review of the entire subject.

The bibliography has been prepared to satisfy those readers whose appetites I have whetted.

My thanks are due to Professor W. J. Gies (Columbia), Colonel W. P. Chamberlain (Medical Corps, U. S. A.), Dr. Casimir Funk (H. A. Metz & Co.), Dr. Arthur Harden (Lister Institute, London), Professor E. V. McCollum (Johns Hopkins), Professor L. B. Mendel (Yale), Dr. E. G. Miller, Jr. (Columbia) and Dr. T. B. Osborne (Connecticut Experimental Station). These gentlemen have helped me in a number of ways.

Professors Gies, Mendel and McCollum, Dr. Funk, Mr. J. E. Whitsit and Mrs. Nellie J. Waller-stein have been kind enough to read the manuscript and to offer many helpful suggestions.

My thanks are also due to the British Medical Research Committee and to the editors of the Journal of the American Medical Association, the Philippine Journal of Science and the Carnegie Institute of Washington for their permission to reproduce drawings.

Benjamin Harrow.

Preface To The Revised Edition

The distinctive features of this edition are (a) the inclusion of a number of experiments conducted at the Columbia laboratory of Physiological Chemistry, in order that certain fundamental facts discussed in this book may be further illustrated; and (b) additions to the work, so that the subject of vitamines may be brought up-to-date. References to all the important papers are given.

Instead of correcting and enlarging the body of the work, it has been thought advisable to include the new matter in the form of an appendix (pages 214 seq). In this way the reader may readily digest the more important advances made in the rapidly growing subject of vitamines during the several months that have elapsed since the appearance of the first edition.

For help in the preparation of this edition my thanks are especially due to Professor W. J. Gies and to Mr. Maxwell Karshan.

Benjamin Harrow.