Bodily changes in pain, hunger, fear, and rage

by Walter B. Cannon

The doctrine of human development from subhuman antecedents has done much to unravel the complex nature of man. As a means of interpretation this doctrine has been directed chiefly toward the solving of puzzles in the peculiarities of anatomical structure. Thus arrangements in the human body, which are without obvious utility, receive rational explanation as being vestiges of parts useful in or characteristic of remote ancestors—parts retained in man because of age-long racial inheritance. This mode of interpretation has proved applicable also in accounting for functional peculiarities. Expressive actions and gestures—the facial appearance in anger, for example—observed in children and in widely distinct races, are found to be innate, and are best explained as the retention in human beings of responses which are similar in character in lower animals.

From this point of view biology has contributed much to clarify our ideas regarding the motives of human behavior. The social philosophies which prevailed during the past century either assumed that conduct was determined by a calculated search for pleasure and avoidance of pain or they ascribed it to a vague and undefined faculty named the conscience or the moral sense. Comparative study of the behavior of men and of lower animals under various circumstances, however, especially with the purpose of learning the source of prevailing impulses, is revealing the inadequacy of the theories of the older psychologists. More and more it is appearing that in men of all races and in most of the higher animals, the springs of action are to be found in the influence of certain emotions which express themselves in characteristic instinctive acts.

The rôle which these fundamental responses in the higher organisms play in the bodily economy has received little attention. As a realm for investigation the bodily changes in emotional excitement have been left by the physiologists to the philosophers and psychologists and to the students of natural history. These students, however, have usually had too slight experience in the detailed examination of bodily functions to permit them to follow the clues which superficial observation might present. In consequence our knowledge of emotional states has been meager.

There are, of course, many surface manifestations of excitement. The contraction of blood vessels with resulting pallor, the pouring out of “cold sweat,” the stopping of saliva-flow so that the “tongue cleaves to the roof of the mouth,” the dilation of the pupils, the rising of the hairs, the rapid beating of the heart, the hurried respiration, the trembling and twitching of the muscles, especially those about the lips—all these bodily changes are well recognized accompaniments of pain and great emotional disturbance, such as fear, horror and deep disgust. But these disturbances of the even routine of life, which have been commonly noted, are mainly superficial and therefore readily observable. Even the increased rapidity of the heart beat is noted at the surface in the pulsing of the arteries. There are, however, other organs, hidden deep in the body, which do not reveal so obviously as the structures near or in the skin, the disturbances of action which attend states of intense feeling. Special methods must be used to determine whether these deep-lying organs also are included in the complex of an emotional[*] agitation.

[*]In the use of the term “emotion” the meaning here is not restricted to violent affective states, but includes “feelings” and other affective experiences. At times, also, in order to avoid awkward expressions, the term is used in the popular manner, as if the “feeling” caused the bodily change.

Among the organs that are affected to an important degree by feelings are those concerned with digestion. And the relations of feelings to the activities of the alimentary canal are of particular interest, because recent investigations have shown that not only are the first stages of the digestive process normally started by the pleasurable taste and smell and sight of food, but also that pain and great emotional excitement can seriously interfere with the starting of the process or its continuation after it has been started. Thus there may be a conflict of feelings and of their bodily accompaniments—a conflict the interesting bearing of which we shall consider later.

Emotions Favorable to Normal Secretion of the Digestive Juices

The feelings or affective states favorable to the digestive functions have been studied fruitfully by Pawlow,[1] of Petrograd, through ingenious experiments on dogs. By the use of careful surgical methods he was able to make a side pouch of a part of the stomach, the cavity of which was wholly separate from the main cavity in which the food was received. This pouch was supplied in a normal manner with nerves and blood vessels, and as it opened to the surface of the body, the amount and character of the gastric juice secreted by it under various conditions could be accurately determined. Secretion by that part of the stomach wall which was included in the pouch was representative of the secretory activities of the entire stomach. The arrangement was particularly advantageous in providing the gastric juice unmixed with food. In some of the animals thus operated upon an opening was also made in the esophagus so that when the food was swallowed, it did not pass to the stomach but dropped out on the way. All the pleasures of eating were thus experienced, and there was no necessity of stopping because of a sense of fulness. This process was called “sham feeding.” The well-being of these animals was carefully attended to, they lived the normal life of dogs, and in the course of months and years became the pets of the laboratory.

By means of sham feeding Pawlow showed that the chewing and swallowing of food which the dogs relished resulted, after a delay of about five minutes, in a flow of natural gastric juice from the side pouch of the stomach—a flow which persisted as long as the dog chewed and swallowed the food, and continued for some time after eating ceased. Evidently the presence of food in the stomach is not a prime condition for gastric secretion. And since the flow occurred only when the dogs had an appetite, and the material presented to them was agreeable, the conclusion was justified that this was a true psychic secretion.

The mere sight or smell of a favorite food may start the pouring out of gastric juice, as was noted many years ago by Bidder and Schmidt[2] in a hungry dog which had a fistulous opening through the body wall into the stomach. This observation, reported in 1852, was confirmed later by Schiff and also still later by Pawlow. That the mouth “waters” with a flow of saliva when palatable food is seen or smelled has long been such common knowledge that the expression, “It makes my mouth water,” is at once recognized as the highest testimony to the attractiveness of an appetizing dish. That the stomach also “waters” in preparation for digesting the food which is to be taken is clearly proved by the above cited observations on the dog.