作者：Crile, George W.
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Origin and Nature of Emotions试读：
PREFACE
IN response to numerous requests I have brought together into this volume eight papers which may serve as a supplement to the volumes previously published[*] and as a preface to monographs now in preparation.
[*] Surgical Shock, 1899; Surgery of the Respiratory System, 1899; Problems Relating to Surgical Operations, 1901; Blood Pressure in Surgery, 1903; Hemorrhage and Transfusion, 1909; Anemia and Resuscitation, 1914; and Anoci-association, 1914 (with Dr. W. E. Lower).
In the first of these addresses, the Ether Day Address, delivered at the Massachusetts General Hospital in October, 1910, I first enunciated the Kinetic Theory of Shock, the key to which was found in laboratory researches and in a study of Darwin's "Expression of the Emotions in Man and in Animals," whereby the phylogenetic origin of the emotions was made manifest and the pathologic identity of surgical and emotional shock was established. Since 1910 my associates and I have continued our researches through— (a) Histologic studies of all the organs and tissues of the body; (b) Estimation of the H-ion concentration of the blood in the emotions of anger and fear and after the application of many other forms of stimuli; (c) Functional tests of the adrenals, and (d) Clinical observations.
It would seem that if the striking changes produced by fear and anger and by physical trauma in the master organ of the body— the brain—were due to WORK, then we should expect to find corresponding histologic changes in other organs of the body as well. We therefore examined every organ and tissue of the bodies of animals which had been subjected to intense fear and anger and to infection and to the action of foreign proteins, some animals being killed immediately; some several hours after the immediate effects of the stimuli had passed; some after seances of strong emotion had been repeated several times during a week or longer.
The examination of all the tissues and organs of these animals showed changes in three organs only, and with few exceptions in all three of these organs—the brain, the adrenals, and the liver. The extent of these changes is well shown by the photomicrographs which illustrate the paper on "The Kinetic System" which is included in this volume. This paper describes many experiments which show that the brain, the adrenal, and the liver play together constantly and that no one of these organs—as far at least as is indicated by the histologic studies—can act without the co-operation of the other two.
Another striking fact which has been experimentally established is that the deterioration of these three organs caused by emotion, by exertion, and by other causes is largely counteracted, if not exclusively, during sleep. If animals exhausted by the continued application of a stimulus are allowed complete rest for a certain number of hours, *without sleep, the characteristic histologic appearance of exhaustion in the brain, adrenals, and liver is not altered notably, whereas in animals allowed to sleep for the same number of hours the histologic changes in these organs are lessened— in some cases obliterated even.
This significant phenomenon and its relation will be dealt with in a later monograph.
Many of the arguments and illustrations by which the primary premises were established are repeated—a few in all—many in more than one of these addresses. It will be observed, however, that the APPLICATION of these premises varies, and that their SIGNIFICANCE broadens progressively.
In the Ether Day Address the phylogenetic key supplied by Darwin was utilized to formulate the principle that the organism reacts as a unit to the stimuli of physical injury, of emotion, of infection, etc. To the study of these reactions (transformations of energy) the epoch-making work of Sherrington, "The Integrative Action of the Nervous System," gave an added key by which the dominating role of the brain was determined. Later the original work of Cannon on the adrenal glands gave facts, and an experimental method by which Darwin's phylogenetic theory of the emotions was further elaborated in other papers, especially in the one entitled "Phylogenetic Association in Relation to the Emotions," read before The American Philosophical Society in April, 1911. GEORGE W. CRILE. CLEVELAND, OHIO, February, 1915.
The discovery of the anesthetic properties of ether and its practical application to surgery must always stand as one of the great achievements of medicine. It is eminently fitting that the anniversary of that notable day, when the possibilities of ether were first made known to the world, should be celebrated within these walls, and whatever the topic of your Ether Day orator, he must fittingly pause first to pay tribute to that great event and to the master surgeons of the Massachusetts General Hospital. On this occasion, on behalf of the dumb animals as well as on behalf of suffering humanity, I express a deep sense of gratitude for the blessings of anesthesia.
Two years ago, an historic appreciation of the discovery of ether was presented here by Professor Welch, and last year an address on medical research was given by President Eliot. I, therefore, will not attempt a general address, but will invite your attention to an experimental and clinical study. In presenting the summaries of the large amount of data in these researches, I acknowledge with gratitude the great assistance rendered by my associates, Dr. D. H. Dolley, Dr. H. G. Sloan, Dr. J. B. Austin, and Dr. M. L. Menten.[*]
[*] From the H. K. Cushing Laboratory of Experimental Medicine,Western Reserve University, Cleveland.
The scope of this paper may be explained by a concrete example. When a barefoot boy steps on a sharp stone there is an immediate discharge of nervous energy in his effort to escape from the wounding stone. This is not a voluntary act. It is not due to his own personal experience— his ontogeny—but is due to the experience of his progenitors during the vast periods of time required for the evolution of the species to which he belongs, i. e., his phylogeny. The wounding stone made an impression upon the nerve receptors in the foot similar to the innumerable injuries which gave origin to this nerve mechanism itself during the boy's vast phylogenetic or ancestral experience. The stone supplied the phylogenetic association, and the appropriate discharge of nervous energy automatically followed. If the sole of the foot be repeatedly bruised or crushed by a stone, shock may be produced; if the stone be only lightly applied, then the consequent sensation of tickling causes a discharge of nervous energy. In like manner there have been implanted in the body other mechanisms of ancestral or phylogenetic origin whose purpose is the discharge of nervous energy for the good of the individual. In this paper I shall discuss the origin and mode of action of some of these mechanisms and their relation to certain phases of anesthesia.
The word anesthesia—meaning WITHOUT FEELING—describes accurately the effect of ether in anesthetic dosage. Although no pain is felt in operations under inhalation anesthesia, the *nerve impulses excited by a surgical operation still reach the brain. We know that not every portion of the brain is fully anesthetized, since surgical anesthesia does not kill. The question then is: What effect has trauma under surgical anesthesia upon the part of the brain THAT REMAINS AWAKE? If, in surgical anesthesia, the traumatic impulses cause an excitation of the wide-awake cells, are the remainder of the cells of the brain, despite anesthesia, affected in any way? If so, they are prevented by the anesthesia from expressing that influence in conscious perception or in muscular action. Whether the ANESTHETIZED cells are influenced or not must be determined by noting the physiologic functions of the body after anesthesia has worn off, and in animals by an examination of the brain-cells as well. It has long been known that the vasomotor, the cardiac, and the respiratory centers discharge energy in response to traumatic stimuli applied to various sensitive regions of the body during surgical anesthesia. If the trauma be sufficient, exhaustion of the entire brain will be observed after the effect of the anesthesia has worn off; that is to say, despite the complete paralysis of voluntary motion and the loss of consciousness due to ether, the traumatic impulses that are known to reach the AWAKE centers in the medulla also reach and influence every other part of the brain. Whether or not the consequent functional depression and the morphologic alterations seen in the brain-cells may be due to the low blood-pressure which follows excessive trauma is shown by the following experiments: The circulation of animals was first rendered STATIC by over-transfusion, and was controlled by a continuous blood-pressure record on a drum, the factor of anemia being thereby wholly excluded during the application of the trauma and during the removal of a specimen of brain tissue for histologic study. In each instance, morphologic changes in the cells of all parts of the brain were found, but it required much more trauma to produce brain-cell changes in animals whose blood-pressure was kept at the normal level than in the animals whose blood-pressure was allowed to take a downward course. In the cortex and in the cerebellum, the changes in the brain-cells were in every instance more marked than in the medulla.
There is also strong NEGATIVE evidence that traumatic impulses are not excluded by ether anesthesia from the part of the brain that is apparently asleep. This evidence is as follows: If the factor of fear be excluded, and if in addition the traumatic impulses be prevented from reaching the brain by cocain[*] blocking, then, despite the intensity or the duration of the trauma within the zone so blocked, there follows no exhaustion after the effect of the anesthetic disappears, and no morphologic changes are noted in the brain-cells.
[*] Since the presentation of this paper, novocain has been substituted for cocain in operations under anoci-association.
Still further negative evidence that inhalation anesthesia offers little or no protection to the brain-cells against trauma is derived from the following experiment: A dog whose spinal cord had been divided at the level of the first dorsal segment, and which had then been kept in good condition for two months, showed a recovery of the spinal reflexes, such as the scratch reflex, etc. Such an animal is known as a "spinal dog." Now, in this animal, the abdomen and hind extremities had no direct nerve connection with the brain. In this dog, continuous severe trauma of the abdominal viscera and of the hind extremities lasting for four
hours was accompanied by but slight change in either the circulation or in the respiration, and by no microscopic alteration of the brain-cells (Fig. 1). Judging from a large number of experiments on NORMAL dogs under ether, such an amount of trauma would have caused not only complete physiologic exhaustion of the brain, but also morphologic alterations of all of the brain-cells and the physical destruction of many (Fig. 2). We must, therefore, conclude that, although ether anesthesia produces unconsciousness, it APPARENTLY PROTECTS NONE OF THE BRAIN-CELLS against exhaustion from the trauma of surgical operations; ether is, so to speak, but a veneer. Under nitrous oxid anesthesia there is approximately only one-fourth as much exhaustion as is produced by equal trauma under ether (Fig. 3). We must conclude, therefore, either that nitrous oxid protects the brain-cells against trauma or that ether predisposes the brain-cells to exhaustion as a result of trauma. With these premises let us now inquire into the cause of this exhaustion of the brain-cells.
The Cause of the Exhaustion of the Brain-cells as a Result of Trauma of Various Parts of the Body under Inhalation Anesthesia
Numerous experiments on animals to determine the effect of ether anesthesia per se, i. e., ether anesthesia without trauma, showed that, although certain changes were produced, these included neither the physiologic exhaustion nor the alterations in the brain-cells which are characteristic of the effects of trauma. On turning to the study of trauma, we at once found in the behavior of individuals as a whole under deep and under light anesthesia the clue to the cause of the discharge of energy, of the consequent physiologic exhaustion, and of the morphologic changes in the brain-cells.
If, in the course of abdominal operations, rough manipulations of the parietal peritoneum be made, there will be frequently observed a marked increase in the respiratory rate and an increase in the expiratory force which may be marked by the production of an audible expiratory groan. Under light ether anesthesia, severe manipulations of the peritoneum often cause such vigorous contractions of the abdominal muscles that the operator is greatly hindered in his work.
Among the unconscious responses to trauma under ether anesthesia are purposeless moving, the withdrawal of the injured part, and, if the anesthesia be sufficiently light and the trauma sufficiently strong, there may be an effort toward escape from the injury. In injury under ether anesthesia every grade of response may be seen, from the slightest change in the respiration or in the blood-pressure to a vigorous defensive struggle. As to the purpose of these subconscious movements in response to injury, there can be no doubt— THEY ARE EFFORTS TO ESCAPE FROM THE INJURY.
Picture what would be the result of a formidable abdominal operation extending over a period of half an hour or more on an unanesthetized human patient, during which extensive adhesions had been broken up, or a large tumor dislodged from its bed! In such a case, would not the nervous system discharge its energy to the utmost in efforts to escape from the injury, and would not the patient suffer complete exhaustion? If the traumata under inhalation anesthesia are sufficiently strong and are repeated in sufficient numbers, the brain-cells are finally deprived of their dischargeable nervous energy and become exhausted just as exhaustion follows such strenuous and prolonged muscular exertion as is seen in endurance tests. Whether the energy of the brain be discharged by injury under anesthesia or by ordinary muscular exertion, identical morphologic changes are seen in the nerve-cells. In shock from injury (Fig. 2), in exhaustion from overwork (Hodge and Dolley) (Fig. 4), and in exhaustion from pure fear (Fig. 5), the resultant general functional weakness is similar— in each case a certain length of time is required to effect recovery, and in each there are morphologic changes in the brain-cells. It is quite clear that in each of these cases the altered function and form of the brain-cells are due to an *excessive discharge of nervous energy. This brings us to the next question: What determines the discharge of energy as a result of trauma with or without inhalation anesthesia?
The Cause of the Discharge of Nervous Energy as a Result of Trauma under Inhalation Anesthesia and under Normal Conditions
I looked into this problem from many viewpoints and there seemed to be no solution until it occurred to me to seek the explanation in certain of the postulates which make up the doctrine of evolution. I realize fully the difficulty and the danger in attempting to reach the generalization which I shall make later and in the hypothesis I shall propose, for there is, of course, no direct final proof of the truth of even the doctrine of evolution. It is idle to consider any experimental research into the cause of phenomena that have developed by natural selection during millions of years. Nature herself has made the experiments on a world-wide scale and the data are before us for interpretation. Darwin could do no more than to collect all available facts and then to frame the hypothesis by which the facts were best harmonized. Sherrington, that masterly physiologist, in his volume entitled "The Integrative Action of the Nervous System," shows clearly how the central nervous system was built up in the process of evolution. Sherrington has made free use of Darwin's doctrine in explaining physiologic functions, just as anatomists have extensively utilized it in the explanation of the genesis of anatomic forms. I shall assume, therefore, that the discharge of nervous energy is accomplished by the application of the laws of inheritance and association, and I conclude that this hypothesis will explain many clinical phenomena. I shall now present such evidence in favor of this hypothesis as time and my limitations will admit, after which I shall point out certain clinical facts that may be explained by this hypothesis.
According to the doctrine of evolution, every function owes its origin to natural selection in the struggle for existence. In the lower and simpler forms of animal life, indeed, in our human progenitors as well, existence depended principally upon the success with which three great purposes were achieved: (1) Self-defense against or escape from enemies; (2) the acquisition of food; and (3) procreation; and these were virtually the only purposes for which nervous energy was discharged. In its last analysis, in a biologic sense, this statement holds true of man today. Disregarding for the present the expenditure of energy for procuring food and for procreation, let us consider the discharge of energy for self-preservation. The mechanisms for self-defense which we now possess were developed in the course of vast periods of time through innumerable intermediary stages from those possessed by the lowest forms of life. One would suppose, therefore, that we must now be in possession of mechanisms which still discharge energy on adequate stimulation, but which are not suited to our present needs. We shall point out some examples of such unnecessary mechanisms. As Sherrington has stated, our skin, in which are implanted many receptors for receiving specific stimuli which are transmitted to the brain, is interposed between ourselves and the environment in which we are immersed. When these stimuli reach the brain, there is a specific response, principally in the form of muscular action. Now, each receptor can be adequately stimulated only by the particular factor or factors in the environment which created the necessity for the existence of that receptor. Thus there have arisen receptors for touch, for temperature, for pain, etc. The receptors for pain have been designated nociceptors (nocuous or harmful) by Sherrington.
On the basis of natural selection, nociceptors could have developed in only those regions of the body which have been exposed to injury during long periods of time. On this ground the finger, because it is exposed, should have many nociceptors, while the brain, though the most important organ of the body, should have no nociceptors because, during a vast period of time, it has been protected by a skull. Realizing that this point is a crucial one, Dr. Sloan and I made a series of careful experiments. The cerebral hemispheres of dogs were exposed by removing the skull and dura under ether and local anesthesia. Then various portions of the hemispheres were slowly but completely destroyed by rubbing them with pieces of gauze. In some instances a hemisphere was destroyed by burning. In no case was there more than a slight response of the centers governing circulation and respiration, and no morphologic change was noted in an histologic study of the brain-cells of the uninjured hemisphere. The experiment was as completely negative as were the experiments on the "spinal dog." Clinically I have confirmed these experimental findings when I have explored the brains of conscious patients with a probe to determine the presence of brain tumors. Such explorations elicited neither pain nor any evidence of altered physiologic functions. The brain, therefore, contains no mechanism— no nociceptors—the direct stimulation of which can cause a discharge of nervous energy in a self-defensive action. That is to say, direct injury of the brain can cause no purposeful nerve-muscular action, while direct injury of the finger does cause purposeful nerve-muscular action. In like manner, the deeper portions of the spinal region have been sheltered from trauma and they, too, show but little power of causing a discharge of nervous energy on receiving trauma. The various tissues and organs of the body are differently endowed with injury receptors—the nociceptors of Sherrington. The abdomen and chest when traumatized stand first in their facility for causing the discharge of nervous energy, i. e., THEY STAND FIRST IN SHOCK PRODUCTION. Then follow the extremities, the neck, and the back. It is an interesting fact also that different types of trauma elicit different responses as far as the consequent discharge of energy is concerned.
Because it is such a commonplace observation, one scarcely realizes the importance of the fact that clean-cut wounds inflicted by a razor-like knife cause the least reaction, while a tearing, crushing trauma causes the greatest response. It is a suggestive fact that the greatest shock is produced by any technic which imitates the methods of attack and of slaughter used by the carnivora. *In the course of evolution, injuries thus produced may well have been the predominating type of traumata to which our progenitors were subjected. In one particular respect there is an analogy between the response to trauma of some parts of the body of the individuals of a species susceptible to shock and the response to trauma of the individuals in certain other great divisions of the animal kingdom. Natural selection has protected the crustaceans against their enemies by protective armor, e. g., the turtle and the armadillo; to the birds, it has given sharp eyes and wings, as, for instance, the wild goose to another species—the skunk—it has given a noisome odor for its protection. The turtle, protected by its armor against trauma, is in a very similar position to that of the sheltered brain of man and, like the brain, the turtle does not respond to trauma by an especially active self-protective nerve-muscular response, but merely withdraws its head and legs within the armored protection. It is proverbially difficult to
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