Investigations made during the past decade have brought forth a discovery of the utmost importance to the well-being of mankind. And the discovery is this: In the foods we eat or should eat there are present very small amounts of certain life-giving and disease-preventing bodies, the consumption of which is essential to growth and good health. Such bodies are called vitamins.

Before the day when the import of vitamins came to be recognized we were well satisfied to believe that an adequate supply of protein, fat, carbohydrate, mineral salts and water met our food requirements fully. Food charts were widely disseminated which made it apparent that the heat units of food, the " calories " available, were the essential factors in the control of a diet or ration. Women's clubs and other organisations were addressed on this score so often and emphatically that many a conscientious housewife kept scales in the kitchen to weigh protein, fat and carbohydrates and thereby compute the daily distribution and consumption of calories.

The common belief of past years, when the calorie or energy value of a diet was the theme, has since been modified. Fuel values are as important of consideration at the present time as they were in earlier yean, but it is now well established that in addition to the body-building and fuel components of foodstuffs, namely, the protein, fat and carbohydrates and also salts and water, we should consume the accessory food substances or factors known as vitamins. That substances playing' so vital a role in nutrition should until a decade ago have escaped discovery is surprising, so much so, in fact, that much incredulity was provoked over the announcement. The brilliant but necessarily laborious researches of investigators in this country supported by original as well as confirmatory work in England and elsewhere have largely overcome this scepticism, much of which apparently emanated from Germany, and have served to make the decade a monumental one in the dietary field. These revelations have made the question' of what to eat an even more necessary matter of "food for thought." With foodstuffs constantly increasing in cost many are disposed to replace one food by another cheaper one on a calorie basis. This cannot be done with impunity.

An understanding of the vitamin requirements of the human organism and of the occurrence of vitamins in edible products as well as the effect of cooking operations on such food factors is needful.

The pronounced differences existing in various proteins due to their varying content of amino acids is no less a vital consideration. The effects of amino acids and the potency of vitamins has become the subject of constant research by a rapidly expanding group of investigators and information is accumulating at a surprising rate concerning the evaluation of foods from new vantage points.

This volume is offered in the endeavor to supply such information in a readily accessible form. It aims to furnish all essential facts regarding vitamins and to bring together the literature on the subject, thus to supply not only a textbook, but also a reference volume of a thoroughly comprehensive nature on these special but highly important phases of the nutrition problem.

The usage of the term vitamin seemingly needs no apology. Criticisms directed towards those workers in the field who have elaborated its fundamentals have made writers cautious in regard to terminology. At present there is little or no knowledge of the actual chemical nature of vitamins but the study of their functions has made most convincing progress. Owing to this feeling of scientific caution, vitamins often have been referred to in very general terms such as " accessory food factors " and their specific forms as fat-soluble A, water-soluble B and the like.

In the light of our present knowledge of vitamins and amino acids, and the noteworthy advances occurring in this domain, the supporters of vegetarianism possibly may find cause for reflection over some of their more extreme theories. A lowering of body tone and subsequent occurrence of symptoms of grave disease may be caused by a lack of vitamins in a diet employed over a series of years. The effects are in a way cumulative. The value of the all-vegetable over the normal diet requires contemplation anew from the vitamin standpoint. In the following pages these and many other features are discussed briefly or expansively according as our present knowledge enables their consideration.

Physicians who have been, charging many of our ills to presence of toxins may have to retract the charges in some cases. It is becoming known that a number of maladies are caused, not by the presence of toxins but by the absence of vitamins. Such knowledge of " deficiency diseases" may lead to substantial changes in medical practice.

The authors have endeavored to make certain portions of the text of a character which would likewise furnish the general reader with a knowledge of the practical side of vitamins including the different requirements by children and adults of these food factors, and if the volume be commended for simplicity of exposition as well as comprehensiveness, the authors will be gratified.

Our thanks are due to the Connecticut Agricultural Experiment Station, the Journal of Biological Chemistry, Professor E. V. Mo-Collum, Professor J. F. McClendon, Dr. A. D. Emmett and associates, Professor H. Steenbock and associates for permission to use illustrations and charts relating to investigations on vitamins, and to Mr. B. Dass for various suggestions and for assistance in the reading of proof.

Ellis Laboratories, 92 greenwood avs, montclair, n. j.

Carleton Ellis.

Vassae College, Poughkenpsin, N. Y.

Annie Louise Maclbod.