Chapter I: Preface

The present book is the outcome of a course of eight lectures delivered before the Lowell Institute of Boston in the early part of 1907.

In this presentation of the subject the attempt has been made to give a systematic account of our knowledge regarding some of the more important processes of nutrition, with special reference to the needs of the body for food. In doing this, the facts accumulated by painstaking observations and experiments during recent years in our laboratory have been incorporated with data from other sources and brought into harmony, so far as possible, with the modern trend of physiological thought.

Numerous experimental results, hitherto unpublished, have been introduced, notably in Chapter VII, in which a few of the data recently obtained in our laboratory with dogs are presented in some detail, since they afford evidence of the error of the current arguments concerning the necessity of a high proteid intake by man, as based on the results of earlier investigators with high proteid animals.

It is hoped that the facts and arguments here presented will help to arouse a more general interest in the subject of human nutrition, as right methods of living promise so much for the health and happiness of the individual and of the community.

CONTENTS

CHAPTER I PAGE

FOODS AND THEIR DIGESTION 1

TOPICS: The purpose of nutrition. The food of man. Proteid foods.
Carbohydrate foods. Fats. Food as fuel. Composition of foodstuffs.
Availability of foods. Food as source of energy. Various factors in
the nourishment of the body. Processes of digestion. Secretion of
saliva. Function of saliva. Enzymes. Reversible action of enzymes.
Specificity of enzymes. Mastication. Gastric secretion. Components
of gastric juice. Action of gastric juice. Muscular movements
of stomach. Time foods remain in stomach. Importance of stomach
digestion. Processes of the small intestine. Secretion of pancreatic
juice. Chemical changes in small intestine. Destruction of proteid
food. Significance of the breaking down of proteid. Change of fatty
foods and carbohydrates in intestine. Digestion practically complete
at end of small intestine. Putrefaction held in check. Digestion a
prelude to utilization of food.