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PHYLOGENETIC ASSOCIATION IN RELATION TO THE
BY GEORGE W. CRILE, M.D.
(Read April 22, 1911.)
To the surgeon every variety of the human emotions in the various stations of life, from infancy to senility, in health and in disease is presented. Not only does the surgeon come in intimate contact with emotions displayed by the victims of disease and accidents but he also observes those manifested by the remainder of the family circle and friends. Then, too, he is unhappily forced to notice the effects upon himself when he is waging an unequal battle against death—the strain and worry at a crisis when a life is in the balance and a single false move may be fatal is an experience unknown to others as it is to the operating surgeon.
My personal experience as a surgeon and an experimental research of my associates, Dr. H. G. Sloan, Dr. J. S. Austin, and Dr. M. L. Menten, and myself furnish data for this paper.
On this occasion I shall limit my discussion mainly to the strongest emotion, viz., fear. I believe that it can be shown that the emotion of fear can be elicited only in animals that utilize a motor mechanism in defense against danger or in escape from it. For example: the defense of the skunk is a diabolic odor which repels its enemies. The skunk has no adequate equipment for defence or escape by muscular exertion. The skunk has little or no fear. Again certain species of snakes are protected by venom. They possess no other means of defense nor adequate motor mechanism for escape. They show no fear. Other animals because of their prowess have but few fears. The lion, the grizzly bear, and the elephant are examples. Animals having armored protection, as the turtle, have little fear. It is therefore obvious that fear is not universal. The emotion of fear is felt only in those animals whose
self-preservation is dependent upon an uncertain adequacy of their power of musçular exertion either in defense or in flight.
What are the principal phenomena of fear? They are palpitation of the heart, acceleration of the rate and alteration of the rhythm of the respiration, cold sweat, rise in body temperature, tremor, pallor, erection of the hair, suspension of the principal functions of digestion, muscular relaxation and staring of the eyes. The function of the brain is wholly suspended except that which
The expression in this picture, copied from “Outing,” shows the participation of the facial muscles in physical action-perhaps it may indicate the origin of the activity of the facial muscles in ancient fighting with teeth.
relates to the self-protective response to the object feared. Neither the brain nor any other organ of the body can respond to any other lesser stimulus during the dominance of fear.
From the foregoing it would appear that under the influence of fear, most, perhaps all of the organs of the body, are divided sharply into two classes: first, those that are stimulated, and second, those that are inhibited. Those that are stimulated are the entire muscular system, vasomotor and locomotor systems, the senses of per
ception, the respiration, the mechanism for erecting the hair, the sweat glands, the thyroid gland, the adrenal gland (Cannon), and the special senses. On the other hand the entire digestive and procreative functions are inhibited. What is the significance of this grouping? So far as we know the organs stimulated increase the efficiency of the animal for fight or for flight. It is through skeletal muscles that the physical attack or escape is affected; these muscles alone energize the claws, the teeth, the hoofs, and the means for flight. The increased action of muscles of the heart and the blood vessels increases the efficiency of the circulation; the secretion of the adrenal gland causes a rise in the blood pressure; the increased action of the thyroid gland causes an increased metabolic activity; there is evidence that glycogen is actively called out, it being the most immediately available substance for the production of energy; the increased activity of the respiration is needed to supply the greater requirements of oxygen and the elimination of the increased amount of waste products; the dilation of the nostrils affords a freer intake of air; the increased activity of the sweat glands is needed to regulate the rising temperature of the body from the increased metabolism. The activity of all of the organs of perception -sight, hearing, smell—are heightened for the purpose of more accurately perceiving the danger. It can not be a mere coincidence that the organs and the tissues that are stimulated in the emotion of fear are precisely those that are actually utilized in the percep
of danger in a physical struggle for self-preservation.
Are there any other organs stimulated by fear except those that can or that do assist in making a defensive struggle? I know of
On the other hand, if an animal could dispense with his bulky digestive organs, whose functions are suspended by fear, if he could, so to speak, clear his decks for battle, it would be advantageous. Although the marvelous versatility of natural selection apparently could devise no means of affording this advantage, it shut off the nervous current and saved the vital force these noncombatants ordinarily consume in the performance of their functions. Whatever the origin of fear is, its phenomena are due to a stimulation of all of the organs and tissues that add to the efficiency
of the physical struggle for self-preservation through the motor mechanism and an inhibition of the function of the leading organs that do not participate—the non-combatants, so to speak. Fear arose from injury, and is one of the oldest and surely the strongest emotion. By the slow process of vast empyricism nature evolved the wonderful defensive motor mechanism of many animals and of man. Now the stimulation of this mechanism leading to a physical struggle is action, and the stimulation of this mechanism without action is emotion.
We may say that fear is a phylogenetic fight or flight. On this hypothesis all the organs and parts of the entire animal are integrated, connected up or correlated, for self-preservation by activity of its motor mechanism. We fear not in our hearts alone, not in our brain alone, not in our viscera alone; fear influences every organ and tissue-each organ or tissue is stimulated or inhibited according to its use or hindrance in the physical struggle for existence. In thus concentrating all or most of the nerve force on the nerve muscular mechanism for defense alone, a greater physical power is developed. Hence, it is that animals under the stimulus of fear are able to perform preternatural feats of strength. Then, too, for the same reason the exhaustion following fear will be the greater, as the powerful stimulus of fear drains the cup of nervous energy, though no visible action may result. An animal under the stimulus of fear may be likened to an automobile with the clutch thrown out but whose engine is racing at top speed. The gasoline is being consumed, the machinery is being worn, but the machine as a whole does not move, though the power of its engine may cause it to tremble.
Applying this conception to human beings of today certain mysterious phenomena are at once elucidated. It must be borne in mind that man has not been presented with any new organs to meet the requirements of his present state of civilization-indeed not only does he possess the same type of organs as his savage fellows but also the same type of organs possessed by even the lower animals. In fact the present status of civilization of man is now operated with the primary equipment of brutish organs. Perhaps the most
striking difference is the greater control man has gained over his primitive instinctive reactions. Contrasted with the entire duration of organic evolution, man has come down from his arboreal abode and assumed his new rôle of increased domination over the physical world but a moment ago. And now, though sitting at his
Fig. 2. Note the resemblance between the facial expression in the great efforts of the athlete and the expression of the strong emotions. The relation of motion and emotion becomes more obvious as strong motor and emotional acts are compared. From “Outing.”
desk in command of a complicated machinery of civilization, when he fears a business catastrophe it is in the terms of his ancestral physical battle in the struggle for existence. He cannot fear intellectually, he cannot fear dispassionately, he fears with all of his