During the past four years there has been conducted, in the Harvard Physiological Laboratory, a series of investigations concerned with the bodily changes which occur in conjunction with pain, hunger and the major emotions. A group of remarkable alterations in the bodily economy have been discovered, all of which can reasonably be regarded as responses that are nicely adapted to the individual’s welfare and preservation. Because these physiological adaptations are interesting both in themselves and in their interpretation, not only to physiologists and psychologists, but to others as well, it has seemed worth while to gather together in convenient form the original accounts of the experiments, which have been published in various American medical and physiological journals. I have, however, attempted to arrange the results and discussions in an orderly and consecutive manner, and I have tried also to eliminate or incidentally to explain the technical terms, so that the exposition will be easily understood by any intelligent reader even though not trained in the medical sciences. My first interest in the conditions attending pain, hunger and strong emotional states was stimulated during the course of a previous series of researches on the motor activities of the alimentary canal. A summary of these researches appeared in 1911, under the title, “The Mechanical Factors of Digestion.” The studies recorded in the present volume may be regarded as a natural sequence of observations on the influence of emotional states on the digestive process, which were reported in that volume. W. B. Cannon. CONTENTS CHAPTER I PAGES THE EFFECT OF THE EMOTIONS ON DIGESTION Emotions favorable to normal secretion of the digestive juices--Emotions unfavorable to normal secretion of the digestive juices--Emotions favorable and unfavorable to contractions of the stomach and intestines--The disturbing effect of pain on digestion 1-21 CHAPTER II THE GENERAL ORGANIZATION OF THE VISCERAL NERVES CONCERNED IN EMOTIONS The outlying neurones--The three divisions of the outlying neurones--The extensive distribution of neurones of the “sympathetic” or thoracico-lumbar division and their arrangement for diffuse action--The arrangement of neurones of the cranial and sacral divisions for specific action--The cranial division a conserver of bodily resources--The sacral division a group of mechanisms for emptying--The sympathetic division antagonistic to both the cranial and the sacral--Neurones of the sympathetic division and adrenal secretion have the same action 22-39 CHAPTER III METHODS OF DEMONSTRATING ADRENAL SECRETION AND ITS NERVOUS CONTROL