Bodily Changes in Pain, Hunger, Fear and Rage

* The name "adrenalin" is proprietary. "Epinephrin" and "adrenin" have been suggested as terms free from commer- cial suggestions. As adrenin is shorter and more clearly related to the common adjectival form, adrenal, I have fol- lowed Schafer in using adrenin to designate the substance produced physiologically by the adrenal glands. tern precisely as if they were receiving nervous impulses. For example, -when adrenin is injected into the blood, it will cause pupils to dilate, hairs to stand erect, blood vessels to be constricted, the activities of the alimentary canal to be inhibited, and sugar to be liberated from the liver. These effects are not prfidueedJhy-action of the substance ' on the central nervous system, but by^ direct ac-j tion on the organ itself.'^ And the effects oc- cur even after the structures have been removed from the body and kept alive artificially. . The adrenals are glands of internal secretion, \ i. e., like the thyroid, parathyroid, and pituitary glands, for example ; they have no connection with the surface of the body, and they'' give out into^,^ the blood the material which they elaborate. /The blood is carried away from each of them by the lumbo-adrenal vein which empties either into the renal vein or directly into the inferior vena cava just anterior to the openings of the renal veins. The adrenal glands are supplied by preganglionic fibres of the autonomic group,* shown in solid line in Fig. 1. This seems an exception to the general rule that gland cells have an outlying neurone between them and the neurones of tho central nervous system. The medulla of the adre- nal gland, however, is composed of modified nerve cells, and may therefore be regarded as offering exceptional conditions.

The foregoing brief sketch of the organization of the autonomic system brings out a number of points that should be of importance as bearing on the nature of the emotions which manifest themselves in the operations of this system. Thus ' it is highly probable that the sympathetic division, because arranged for diffuse discharge, is likely to be brought into activity as a whole, whereas the sacral and cranial divisions, arranged for particular action on separate organs, may operate , in parts. Also, because antagonisms exist be- ^' tween the middle and either end division of the autonomic, affective states may be classified ac- cording to their expression in the middle or an end division and these states would be, like the nerves, antagonistic in character. And finally, since the adrenal glands are innervated by au- tonomic fibres of the mid-division, and since ad- renal secretion stimulates the same activities that are stimulated nervously by this division, it is possible that disturbances in the realm of the sympathetic, although initiated by nervous dis- charge, are .automatically augmented and pro- longed through chemical effects of the adrenal secretion.

" For a summary of his studies of the organization of the autonomic system, see Langley: Ergebnisse der Physiologie, Wiesbaden, 1903, ii^, p. 818. ^ See Cannon : American Journal of Physiology, 1905, xiii, p. xxii. * See Sherrington : The Integrative Action of the Nerv- ous System, New York, 1909, p. 19. As stated in the first chapter, the inhibition of gastric secretion produced by great excitement long outlasts the presence of the object which' evokes the excitement. The dog that was en- raged by seeing a cat for five minutes secreted only a few drops of gastric juice during the next fifteen minutes. Why did the state of excitation persist so long after the period of stimulation had ended? This question, which presented itself to me while reading Bickel and Sasaki's paper, fur- nished the suggestion expressed at the close of the last chapter, that the excitement might pro- voke a flow of adrenal secretion, and that the changes originally induced in the digestive organs by nervous impulses might be continued by circu- lating adrenin. The prolongation of the effect might be thus explained. Whether that idea is correct or not has not been tested. Its chief serv- ice was ia leading to an enquiry as to whether

the adrenal glands are in fact stimulated to action in emotional excitement. The preganglionic fibres passing to the glands are contained in the splanch- nic nerves. What is the effect of splanchnic stim- ulation? The Evidence that Splanchnic Stimulation Induces Adrenal Secretion It was in 1891 that Jacobi ^ described nerve fibres derived from the splanchnic trunks which were distributed to the adrenal glands. Six years later BiedP found that these nerves conveyed vaso-dilator impulses to the glands, and he sug- gested that they probably conveyed also secre- tory impulses. Evidence in support of this sug- gestion was presented the following year by Dreyer,^ who demonstrated that electrical ex- citation of the splanchnic nerves produced in the blood taken from the adrenal veins an increased amount of a substance having the power of rais- ing arterial blood pressure, and that this result was independent of accompanying changes in the blood supply to the glands. The conclusion drawn by Dreyer that this substance was adrenin has been confirmed in various ways by later observers. Tscheboksaroff * repeated Dreyer's procedure and found in blood taken from the veins after splanchnic stimulation evidences of the presence of adrenin that were previously absent. Asher ®

observed a rise of blood pressure when tbe glands were stimulated in such, a ma-nner as not to cause constriction of the arteries — the rise was there- fore assumed to be due to secreted adrenin. Dilation of the pupil was used by Meltzer and Joseph « to prove secretory action of the splanch- nics on the adrenal glands ; they found that stim- ulation of the distal portion of the cut splanchnic nerve caused the pupil to enlarge— an effect char- acteristic of adrenin circulating in the blood. Elliott '^ repeated this procedure, but made it a more rigorous proof of internal secretion of the adrenals by noting that the effect failed to ap- pear if the gland on the stimulated side was re- moved. Additional proof was brought by myself and Lyman * when we found that the typical drop in arterial pressure produced in cats by in- jecting small amounts of adrenin could be ex- actly reproduced by stimulating the splanchnic nerves after the abdominal blood vessels, which contract when these nerves are excited, were tied so that no changes iu them could occur to in- fluence the rest of the circulation.

The problem of splanchnic influence on the ad- renal glands Elliott attacked by a still different method. Using, as a measure, the graded effects of graded amounts of adrenin on blood pressure, he was able to assay the quantity of adrenin in adrenal glands after various conditions had been allowed to prevail. The tests were made on cats. In these animals each adrenal gland is supplied only by the splanchnic fibres of its own side, and the two glands normally contain almost exactly the same amount of adrenin. Elliott ^ found that when the gland on one side was isolated by cutting its splanchnic supply, and then impulses were sent along the intact nerves of the other side, either by disturbing the animal or by artificial excita- tion of the nerves, the gland to which these fibres reached invariably contained less adrenin, often very much less, than the isolated gland. Results obtained by the method employed by Elliott have been confirmed with remarkable exactness in re- sults obtained by Folin, Denis and myself,^" using a highly sensitive color test after adding the gland extract to a solution of phosphotungstic acid.

All these observations, with a variety of meth- ods, and by a respectable number of reliable in- vestigators, are harmonious in bringing proof that artificial stimulation of the nerves leading to the adrenal glands will induce secretory ac- tivity in the adrenal medulla, and that in conse- quence adrenin will be increased in the blood. The fact is therefore securely established that in the body a mechanism exists by which these glands can be made to discharge this peculiar sub- stance promptly into the circulation.

As we have already seen, the phenomena of a great emotional disturbance in an animal indi- cate that sympathetic impulses dominate the vis- cera. When, for example, a cat becomes fright- ened, the pupils dilate, the activities of the stomach and intestines are inhibited, the heart beats rapidly, the hairs of the back and tail stand erect — from one end of the ailimal to the other there are abundant signs of nervous discharges along sympathetic courses. Do not the adrenal glands share in this widespread subjugation of the viscera to sympathetic control?

This question, whether the common excitements of an animal's life might be capable of evoking a discharge of adrenin, was taken up by D. de la Paz and myself in 1910. "We made use of the nat- ural enmity between two laboratory animals, the dog and the cat, to pursue our experiments. In these experiments the cat, fastened in a comfor- table holder (the holder already mentioned as be- ing used in X-ray studies of the movements of the alimentary canal), was placed near a barking dog. Some cats when thus treated showed al- most no signs of fear; others, with scarcely a movement of defence, presented the typical pic- ture. In favorable cases the excitement was al- lowed to prevail for five or ten minutes, and in

a few cases longer. Samples of blood were taken within a few minutes before and after tbe period. The blood was obtained from the inferior vena cava anterior to the opening of the adrenal veins, i. e., at a point inside the body near the level of the notch at the lower end of the sternum. To get the blood so far from the surface without disturbing the animal was at first a difficult prob- lem. We found, however, that by making anes- thetic with ethyl chloride the skin directly over the femoral vein high in the groin, the vein could be quickly bared, cleared of connective tissue, tied, and opened without causing any general dis- turbance whatever. A long, fine, flexible catheter (2.4 millimeters in diameter) which had pre- viously been coated with vaseline inside and out, to lubricate it and to delay the clotting of blood within it, was now introduced into the opening in the femoral vein, thence through the iliac and on into the inferior cava to a point near the level of the sternal notch. A thread tied around this tube where, after being inserted to the proper dis- tance, it disappeared into the femoral vein, marked the extent of insertion, and permitted a later introduction to the same extent. This slight operation — a venesection, commonly practised on

our ancestors — consumed only a few minutes, and as the only possibility of causing pain was guarded against by local anesthesia, the animal remained tranquil throughout. Occasionally it was necessary to stroke the cat's head gently to keep her quiet on the holder, and under such cir- cumstances I have known her to purr during all the preparations for obtaining the blood, and while the blood was being taken. The blood (3 or 4 cubic centimetres) was slowly drawn through the catheter into a clean glass syringe. Care was taken to avoid any marked suction such as might cause collapse of the vein near the inner opening of the tube. As soon as the blood was secured, the catheter was removed and the vein tied loosely, to prevent bleeding. The blood was at once emptied into a beaker, and the fibrin whipped from it by means of fringed rubber tubing fitted over a glass rod. Since this defibrinated blood was obtained while the ani- mal was undisturbed, it was labelled "quiet blood."

The animal was then exposed to the barking dog, as already described, and immediately there- after blood was again removed, from precisely the same region as before. This sample, after being defibrinated, was labelled "excited blood." The two samples, the "quiet" and the "excited," both obtained in the same manner and subse- quently treated in the same manner, were now tested for their content of adrenin. It was desirable to use as a test tissues to which the blood was naturally related. As will be recalled, adrenin affects viscera even after they have been removed from the body, just as if they were receiving impulses via sympathetic fibres, and further, that sympathetic fibres nor- mally deliver impulses which cause contraction of the internal genitals and relaxation of the stomach and intestines. The uterus has long been employed as a test for adrenin, the presence of which it indicates by increased contraction. That isolated strips of the longitudinal muscle of the intestine, which are contracting rhythmically, are characteristically inhibited by adrenin in dilu- tions of 1 part in 20 millions, had been shown by Magnus in 1905. Although, previous to our in- vestigation in 1910, this extremely delicate reac- tion had not been used as a biological signal for adrenin, it possesses noteworthy advantages over other methods. The intestine is found in all ani- mals and not in only half of them, as is the uterus ; it is ready for the test within a few minutes, in- stead of the several hours said to be required for the best use of the uterus preparation;" and it responds by relaxing. This last characteristic

is especially important, for in defibrinated blood there are, besides adrenin, other substances cap- able of causing contraction of smooth muscle," and liable therefore to lead to erroneous con- clusions when a structure which responds by con- tracting, such as uterus or artery, is used to prove whether adrenin is present. On the other hand, substances producing relaxation of smooth muscle are few, and are unusual in blood.^* We used, therefore, the strip of intestinal mus- cle as an indicator. Later Ho skins ^* modified our procedure by taking, instead of the strip, a short segment of the rabbit intestine. The seg- ment is not subjected to danger of injury during its preparation, and when fresh it is almost in- credibly sensitive. It may be noticeably inhibited by adrenin, 1 part in 200 millions!

The strip, or the intestinal segment, was sus- pended between minute wire pincers {serres fines) in a cylindrical chamber 8 millimeters in diameter and 5 centimeters deep. By a thread attached to the lower serre fime the preparation was drawn into the chamber, and was held firmly ; by the upper one it was attached to the short end of a writing lever (see Fig. 2). When not ex- posed to blood, the strip was immersed in a nor- mal solution of the blood salts (Einger's). The blood or the salt solution could be quickly with- drawn from or introduced into the chamber, with-

out disturbing the muscle, by means of a fine pipette passed down along the inner surface. The chamber and its contents, the stock of Ringer's Figure 2. — Diagram of the arrangements for recording con- tractions of the intestinal muscle. solution, and the samples of "quiet" and "ex- cited" blood were all surrounded by a large vol- ume of water kept approximately at body tem- perature (37° C). Through the blood or the salt solution in the chamber oxygen was passed in a slow but steady stream of bubbles. Under these circumstances the strip will live for hours, and will contract and relax in a beautifully regular rhythm, which may be recorded graphically by the writing lever.

The first effect of surrounding the muscle with blood, whether "quiet" or "excited," was to send it into a strong contraction which might persist, sometimes with slight oscillations, for a minute or two (see Figs. 4 and 5). After the initial short- ening, the strip, if in quiet blood soon began to contract and relax rhythmically and with each re- laxation to lengthen more, until a fairly even base line appeared in the written record. At this stage the addition of fresh "quiet" blood usually had no effect, even though the strip were washed once with Einger's solution before the second por- tion of the blood was added. For comparison of the effects of "quiet" and "excited" blood on the contracting strip, the two samples were each added to the muscle immediately after the Eing- er's solution had been removed, or they were ap- plied to the muscle alternately and the differences in effect then noted. The results obtained by these methods are next to be presented.

1 Jacobi : Archiv f iir experimentelle Pathologie und Phar- makologie, 1891, xxix, p. 185. * Tscheboksaroff : Archiv f iir die gesammte Physiologie, 1910, cxxxvii, p. 103. ^^ See O'Connor : Archiv fiir die experimentelle Patholo- gie und Pharmakologie, 1912, Ixvii, p. 206. ^*Hoskins: Journal of Pharmacology and Experimental Therapeutics, 1911, iii, p. 95. If the secretion of adrenin is increased in strong emotional states and in pain, that constitutes a fact of considerable significance, for, as already mentioned, adremn is capable of_grodncing many IJf of the bodily changes which are characteristically manifested in emotional and painful experiences, rt is a matter of prime importance for further discussion to determine whether the adrenal glands are in fact roused to special activity in times of stress.

The Evidence that Adrenal Secretion Is Increased in Emotional Excitement That blood from the adrenal veins causes the relaxation of intestinal muscle characteristic of adrenal extract or adrenin is shown in Fig. 3. The muscle was originally beating in blood which contained no demonstrable amount of adrenal se- cretion ; this inactive blood was replaced by blood from the adrenal veins, obtained after quick etherization. Etherization, it will be recalled, is accompanied by a "stage of excitement." Re- laxation occurred almost immediately (at b). Then the rhythm was renewed in the former

FiGtTBB 3. — ^Intestinal muscle beat- ing in inactive blood, which was with- drawn from the chamber at a. Blood from the adrenal vein of an animal ex- cited by etherization was substituted at b, and withdrawn at c. Contrac- tions were restored in the original in- active blood which was removed at d. Blood from the renal vein (same ani- mal) was added at e. In this and subsequent records time is marked in half minutes. blood, and thereupon the muscle was surrounded with blood from the vein leading away from the left kidney, i. e., blood obtained from the same animal and under the same conditions as the adrenal blood, but from a neighboring vein. No relaxation occurred. By this and other similar tests the reliability of the method was proved.

In no instance did blood from the inferior vena cava of the quiet normal animal produce relaxa- tion. On the other hand, blood from the animal after emotional excitement showed more or less promptly the typical relaxation. In Fig. 4 is Figure 4. — Alternate application of "excited" blood (at 6 and/) and "quiet" blood (at d), from the same animal, to in- testinal muscle initially beating in Ringer's solution. represented the record of intestinal muscle which was beating regularly in Einger's solution. At a the Einger's solution was removed, and at b "ex- cited" blood was added; after the preliminary shortening, which, as already stated, occurs at the first immersion in blood, the muscle length- ened gradually into complete inhibition. At c the "excited" blood was removed, and at d "quiet" blood was added in its place. The muscle at once began, fairly regular rhythmic beats. At e the "quiet" blood was removed, and at / the "excited" blood was again applied. The muscle lengthened almost immediately into an inhibited state. In this instance the "excited" blood was taken after

The increase of effect with prolongation of the period of excitement is shown in Fig. 5. A is the Figure 5. — The effect of prolonging the excitement. A, the record in "quiet" serum; B, in defibrinated blood after eleven minutes of excitement; and C, in serum after fifteen minutes of excitement. record of contractions after the muscle was sur- rounded with "quiet" blood serum. B shows the gradual inhibition which occurred when the mus- cle was surrounded with defibrinated blood taken when the animal had been excited eleven minutes. And C is the record of rapid inhibition after fif- teen minutes of excitement. In other instances the effect was manifested merely by a lowering of the tonus of the muscle, and a notable slowing of the beats, without, however, a total abolition of them.

The inference that this inhibition of contrac- tion of the intestinal muscle is due to an increased amount of adrenal secretion in the "excited" blood de la Paz and I justified on several grounds : (1) The inhibition was produced by "excited" blood from the inferior vena cava anterior to the mouths of the adrenal veins, when blood from the femoral vein, taken at the same time, had no in- hibitory influence. Since blood from the femoral vein is typical of the cava blood below the en- trance of the kidney veins, the conclusion is war- ranted that the difference of effect of the two samples of blood is not due to any agent below the kidneys. But that blood from the kidneys does not cause the relaxation is shown in Fig. 3.

FiGTJRB 6. — Failure of the cava blood (added at a) to produce inhibition when excitement has occurred after removal of the adrenal glands. The muscle later proved sensitive to adrenin in blood in the ratio 1:1,000,000. The only other structures which could alter the blood between the two points at which it was taken are the adrenal glands, and the material secreted by them would produce precisely the inhibition of contraction which was in fact pro- duced.

(2) If in ether anesthesia the blood vessels leading to and from the adrenal glands are first carefully tied, and then the glands are removed, ex- citement four or five hours later, before the weak- ness that follows the removal has become promi- nent, does not alter the blood so that the typical inhibition occurs (see Fig. 6). Thus, although the animal shows all the characteristic signs of sympathetic stimulation, the blood, in the absence of the adrenals, remains unchanged.

duced by the "excited" blood was prompt inbibi- tion, sometimes tbe inhibition followed only after several beats, and sometimes a slowing and short- ening of contractions, with a lower tone, were the sole signs of the action of adrenin. All these degrees of relaxation can be duplicated by adding to inactive blood varying amounts of adrenin. Fig. 7 shows the effects, on a somewhat insensi- tive muscle preparation, of adding adrenin, 1:1,000,000 (A), 1:2,000,000 (B), and 1:3,000,000 (C), to different samples of blood joreviously with- out inhibitory influence. These effects of adrenin and the effects produced by blood taken near the opening of the adrenal veins are strikingly analo- gous.

(4) Emden and v. Furth ^ have reported that 0.1 gram of suprarenin chloride disappears almost completely in two hours if added to 200 cubic centimeters of defibrinated beef blood, and the mixture constantly aerated at body temperature. "Excited" blood which produces inhibition loses that power on standing in the cold for twenty-four hours, or on being kept warm and agitated with bubbling oxygen. This change is illustrated in Fig. 8 ; the power of the "excited" blood to inhibit the contractions of the intestinal muscle when rec- ord A was written was destroyed after three hours of exposure to bubbling oxygen, as shown by record B. The destruction of adrenin and

the disappearance of the effect which adrenin would produce are thus closely parallel. Figure 8.— The effect of bubbling oxygen through active blood. A, re- laxation after active blood applied at a; B, failure of relaxation when the same blood, oxygenated three hours, was appHed to a fresh strip at b. that sympathetic impulses increase secretion of the adrenal glands, and taken also with the evidence that, during such emotional excitement as was em- ployed in these experiments, signs of sympathetic discharges appeared throughout the animal from the dilated pupil of the eye to the standing hairs of the tail-tip, led us to the conclusions that the characteristic action of adrenin on intestinal mus- cle was in fact, in our experiments, due to secre- tion of the adrenal glands, and that that secretion is increased in great emotion.

As mentioned in the first chapter, stimulation of sensory fibres in one of the larger nerve trunks is known to result in such nervous discliarges along sympathetic paths as to produce marked inhibi- tion of digestive processes. Other manifestations of sympathetic innervations — e. g., contraction of arterioles, dilation of pupils, erection of hairs — are also demonstrable. And since the adrenal glands are stimulated to activity by sympathetic impulses, it was possible that they would be af- fected as are other structures supplied with sym- pathetic fibres, and that they would secrete in greater abundance when sensory nerves were irri- tated.

The testing of this possibility was undertaken by Hoskins and myself in 1911. Since bodily changes from "painful" stimulation can in large degree be produced in an anesthetized animal, without, how- ever, an experience of pain by the animal, it was possible to make the test quite simply. The sen- sory stimulus was a rapidly interrupted induced current applied to the sciatic nerve. The current was increased in strength as time passed, and thus the intensity of the effect, indicated by continuous dilation of the pupils, was maintained. There was no doubt that such stimulation would have caused very severe pain if the animal had not been anes- thetized. Indeed, the stimulus used was probably much stronger than would be necessary to obtain a positive result in the absence of the anesthetic (urethane), which markedly lessens the irritabil-

ity of visceral nerve fibres.^ In different in- stances the stimulation lasted from three to six minutes. Throughout the period there was mark- edly increased rapidity and depth of breathing. As Fig. 9 shows, the normal blood, removed FiGXTEB 9. — Intestinal mus- cle beating in normal vena cava blood, removed at 1 and re- newed at 2. At 3 normal blood removed. At 4 contraction in- hibited by vena cava blood drawn after sensory stimula- tion; at 5 removed. At 6 Rin- ger's solution substituted.