Two

ASPECTS OF PAIN

1. THE NATURE OF ANIMAL SUFFERING

"Not Can They Reason? nor Can They Talk? but Can They Suffer?"

The French philosopher Descartes (1596- 1650), convinced that animals were mechanistic beings without reason, thought or language, opened the door to centuries of animal torture in the name of science. The 18th century philosopher Jeremy Bentham, whose oft quoted rejoinder heads this chapter, thought that reason and language were irrelevant to the fact of an animal's suffering. Although it is hard to imagine anyone nowadays thinking that a dog's yelp when kicked is merely the "creaking of the machine," there is still an attitude held by some that "animals don't feel pain as we do." In refutation, here is a forceful statement on the subject by two scientists, G.F. Poggio and V.B. Mountcastle (Poggio,C.,1960, p.302).

"We are well aware of the difficulty one faces in labeling as painful any stimulus delivered to an experimental animal, for no introspective report is available. Nevertheless, when a stimulus is by nature destructive of tissue, provokes a defense or escape maneuver accompanied by signs of an appropriate emotional change in the normal working animal, and evokes painful sensations when applied to man, it seems reason able to regard the stimulus as painful in nature to both animal and man. To label such stimuli as 'tissue-destructive, escape-provoking, and emotion-changing', but not to call them painful, seems to us a semantic triviality. There is no a priori reason to suppose that in evolution the perception of pain appears as a wholly new sensory phenomenon in man."

In fact, such a supposition would be quite illogical in view of the neurophysiological similarity between humans and animals. Neurons, synapses - the nerve cells and their connections - and the neuroendocrine mechanisms - the electrical and biochemical paths of communication - are functionally identical through many species; it is therefore inconceivable that there could be radical discontinuity between these patterns of nervous response and the consciousness of pain, mediated in humans by these very mechanisms and of such obvious value to most if not all animals for self-preservation. The ways of evolution are often devious and surprising but they are never unparsimonious1.


Misreading the Pain Signals

However, to say that organs have practically identical functions is not to say that they are identical in structure. A man and a mouse would both jump away from a hot iron, but men and mice are put together very differently and are not often mistaken for one another! Internally, too, although made out of the same materials, the architecture may be different. This may result in a misreading of the pain signals. "In animals," says Lumb "the fiber systems subserving pain perception are more diffuse than in man and are not so easily destroyed. Therefore, it should not be assumed that animals are not perceiving pain because man, in a similar situation, does not." (Lumb, W., 1973, p.67).

A further difficulty arises because animals may not communicate their distress in a sufficiently 'human' fashion. Dogs in pain may show much restlessness, but cats may simply sit in stoical silence.

Still another caution against equating pain-signalling in man with that in animals springs from the fact that man, a social being, has learned from earliest infancy that a display of fear and pain to others may bring help. But a similar display in many non-social animals is avoided because it is likely to attract aggression, especially from predators, rather than assistance. (Baker, J, 1948).

Fear and Pain

The failure to recognize the nature of pain or distress in animals, and probably the subconscious wish of many investigators to deny that their experiments are stressful, result in the reluctance to use pain-relievers to the extent that common humanity would demand. It is not only inhumane, it may distort research findings. M.R. Chance has shown that variations in the environment of rats, for example, will affect the results of tests - based on ovary weights - in standardizing gonadotrophic hormone. These variations included changing the rats' cages, changing the number of their cage-mates, putting them with strange rats rather than litter-mates, and so forth. When such comparatively minor environmental tensions can interfere with test results, it is obvious that unrelieved pain and fear will cause much wider variations. (Chance, M.,1956).

Harold Hillman, a physiologist at the University of Surrey, England, has enumerated the many physiological reactions of an animal in fear and pain.

"An animal under stress, 1. secretes adrenalin from the suprarenal gland into the blood, which raises the blood pressure and heart rate, mobilizes glucose from muscle and liver glycogen; 2. has violent muscular contractions, breaking down creatine phosphate, and accelerating glycolysis, releasing lactic acid into the circulation; 3. hyperventilates, and thus lowers carbon dioxide and increases the blood oxygen tension; 4. increases its metabolic rate and temperature, and changes the pattern of a series of enzyme reactions, each of them dependent to different degrees on the temperature. In summary, there is hardly a single organ or biochemical system in the body which is unaffected by stress .... The changes in some of the parameters cited may be up to 300% of the normal values at rest. This would obviously invalidate painful experiments claiming to examine any changes less than those already known to be due to stress itself. It is almost certainly the main reason for the wide variation reported among animals upon whom painful experiments have been done." (Hillman,H.,1970).

An animal under stress shares all the above reactions with man. The actual perception of pain in man and presumably in animals is influenced by what H.K. Beecher has called the "reaction component," the psychological evaluation of the stress and its significance to the sufferer. Soldiers wounded in combat who interpret the trauma as a fortunate means of release from dangerous service often feel only minimal pain. Volunteers in painful experiments, since no serious outcome is anticipated, also, like the soldiers, suffer relatively little. Analgesics, since they act primarily on psychological distress, are not very effective in these cases.

But when the reaction component is fraught with fear and anxiety as in the case of "pathological pain" from conditions such as cancer - pain of serious and depressive significance - then suffering is much greater, although, fortunately, narcotics are correspondingly more effective. In animals all pain is serious and significant, like pathological pain in man. Therefore analgesics are especially needed in animals and are very effective. (Keele,C.,1962).


2. PAINFUL ELECTRICAL STIMULATION OF THE BRAIN

The term "vivisection," with its etymology derived from "alive" and "to cut," originated during an historical period when experiments were chiefly operations on unanesthetized animals. Although those who call themselves "anti-vivisectionists" today define it much more broadly, the term has greatly obscured the fact that the vast majority of modern pain-inflicting experiments use techniques unknown to our forbears. An example is the electrical probing and shocking ("stimulating" to use the more seemly language of the investigator) of areas, nerve cells or fibres in the brain which register pain. Antiquated laws to prevent "surgical" pain frequently result in the anomaly of an animal having to be carefully anesthetized for the implantation of electrodes through scalp and brain coverings, only to be brought out of anesthesia to experience the unimaginable suffering of direct electrical stimulation of the pain centers in the brain itself. For instance, consider the painful experiments performed on ten cats at the State University of Iowa, Iowa City, in 1976.

"These studies," the university reported, "involve the tracing of central pain pathways in chronically implanted electrodes in the brain of the cat. Tranquilizers or anesthetics would negate the pain and thus would prevent the fulfillment of the protocol of the research. The pain is produced only during 60 second or less time periods when the animals are either stimulated through chronically implanted tooth pulp or intracephalic electrodes." (USDA/APHIS,1976, Iowa,Univ.).

I wrote "unimaginable suffering", above, because humans are never subjected to such experiments (even specialists in political torture have not yet introduced the technique, although no doubt they will).2 Furthermore, pain suffered by an animal is always unmitigated by the 'philosophy' whereby man can often temper his perception of pain.

An experiment of this type by R.S. Kestenbaum of the State University of New York at Stony Brook, E.E. Coons of New York University and another investigator, used 19 rats, the pain receptors in whose brains were electrically stimulated by surgically implanted electrodes. To be sure that the implantation had reached a pain center, they only used those animals which showed "clearly aversive response to the stimulation, such as squealing, defecation, urination and running." Each "one-minute train of noxious midbrain stimulation" could be interrupted, but only for 3 seconds, if the rat pressed an escape lever. The investigators reported that "due to the stressful nature of the stimulation some subjects could only be tested for brief sessions. Thus, an experimental session consisted of 20-60 1-min. brain stimulation trials, each followed by a 1-min. rest." It is not stated just how "some subjects" made it known that the agony, prolonged sometime up to an hour, was more than they could bear. In such an experiment there was no question, of course, of using a pain relieving drug. (Kestenbaum, R., 1973).

The Psychophysiology of Pain

The description of the above experiments brings us into the laboratory, and in the remainder of this chapter I shall examine a few of the procedures which are used in brain experiments to investigate the nature of pain. I have mentioned some of the psychological determinants of the pain experience in humans and what these are, presumably, in animals. But since many experimenters are preoccupied with neurophysiological and neuroanatomical explorations of the brain and central nervous system, I shall broaden the discussion and attempt to attach physiology to psychology as an introduction to these pain experiments.

If our skin is burned or traumatized two things happen: we are conscious of a very unpleasant sensation and we jerk or jump away from the source of the pain. We may quickly rub the skin, or run cold water on it to diminish the pain. If at the time of the hurt we had been under some strong emotion, or if our attention had been intensely fixed on something else, we might at first not have noticed the pain very much.

These reactions can be explained very roughly by the following: although the sensation of pain and the muscular reaction appear to follow the trauma almost instantaneously, in fact a good many things happen between the moment of trauma and the response. The feeling of pain, its intensity, can be decreased - and it can also be increased - by messages which rush down from the brain, messages moulded by the factors of memory, attention and emotion. (The messages conveying emotion, motivating "flight or fight," mostly come from the "limbic" system in the midbrain; attention and memory messages come chiefly from the higher cortical areas.) Hypnotic analgesia, for instance, is caused by the mind's attention being totally absorbed, through hypnotic suggestion, in something other than the sensation of pain. An impulse to flinch from a hypodermic can be inhibited by a memory that the anticipated pain will not be so bad after all. And the sensations from rubbing or chilling the skin can inhibit the pain, if the latter is not too intense, by moving much faster to the brain through the large-diameter fibers which convey them than does the pain sensation through its small fibers. Thus the brain can be triggered into inattention and the pain does not register. Acupuncture probably works via the same mechanism: pricking by needles travels as nerve impulses in large fibers and is felt in the skin as a discrete stimulus which is predominant over diffuse pain - again, if the latter is not too intense.

The neuroanatomical structures forming the substrate of these responses have been examined by researchers over many decades in both humans and animals. For example, K.V. Anderson and associates at Emory University, Atlanta, gave young cats electric shocks to the paws to activate the discrete pain pathways, and shocks to the upper canine teeth to activate the diffuse pain pathways. The cats were trained to jump over a small barrier to escape foot shock, but when the shocks to the teeth were given at the same time, the "animals assumed a fixed posture with limbs extended until both stimuli were terminated." In continued trials pairing tooth and foot shock, escape responses were absent, even though foot shock was raised to - "the maximum amount of current that could be generated by our apparatus." The experimenters convinced themselves that 1 mA shocks to the teeth did not hurt the cats too much, but apparently they hurt enough to reverse the acupuncture effect - the predominance of discrete over diffuse pain stimuli. (Anderson, K.,1976).


Painful Brain Stimulation in Humans

Memory was mentioned above as one of the contributions which the brain makes to the shaping of incoming pain sensations. When a limb has been amputated, sometimes the infusion of -memory appears in the shape of "phantom limb", which gives the patient the sensation that the amputated extremity is still present. Since this phenomenon is usually accompanied by severe pain, neurosurgeons attempt to relieve it by cutting one of the nerve tracts which formerly connected the brain and the limb. B.S. Nashold, Jr. and associates at Duke University Medical Center reported on several cases of phantom limb which had been unsuccessfully treated by this type of surgery, as well as others who were also suffering from intractable pain of central nervous system origin. All of these Nashold et al. planned to treat by interrupting the ascending pain tracts, but only after electrode exploration in the conscious patient of the exact areas involved in the pain sensations. Their report of these preliminary explorations has given us an invaluable insight into the character and degree of pain produced by electrical probing of the pain centers in the midbrain or "mesencephalon." The results can be summarized as follows: 1. stimulation of the gray matter immediately surrounding the central canal in the midbrain ("periaqueductal gray matter") produced diffuse pain with feelings described as "fearful", "frightful" or "terrible"- followed by refusal by the patient to allow it to continue. 2. Stimulation of the areas lateral to this caused a "brighter" or "sharper" sensation of pain, localized on the opposite side of the body, with the patient allowing repeated stimulation because the pain although intense was bearable. (Nashold, B.,1969).

We now know why the monkeys stimulated at Yale University by José Delgado in the same central midbrain area reacted with "high pitched vocalization accompanied by grimacing, restlessness, and attempts to grab and bite objects within reach... with signs of aggressiveness directed against the investigator." (Delgado, J.,1966).


Risks and Precautions in Experiments on Animals Paralyzed by Curariform Drugs

An Editorial Note entitled "Use of Curariform. Agents" in the journal Experimental Neurology (Doty,R.,1975), by R.W. Doty, contains the following admonitions, with a reference (4) to the Nashold article:

"At one time it was common practice to apply electrical stimulation to the brain stem of curarized animals ... with roving electrodes. A large body of evidence has now accumulated on experimental animals and human patients (4) showing that even moderate electrical stimulation of certain regions of the limbic system or mesencephalon can produce aversive effects of extraordinary intensity. While it is not common to strike such loci when using relatively weak stimuli, there is also no certain way of avoiding them, especially in the mesencephalon. The relative inaccuracy of stereotaxic placements and the need to use stimuli likely to be suprathreshold for the "aversive areas" should they be encountered, makes the risk significant that, sooner or later, such regions will be stimulated. In addition, there is probably no reliable method for knowing in the curarized animal whether the stimulation is aversive. Aware of these facts, few experimenters choose to move stimulating electrodes through the brain stem of conscious, curarized animals, any more than they would perform major surgery under these conditions."

Earlier in the editorial, Doty described how an animal's head, in these brain experiments, can be precisely positioned by metal clamps (stereotaxis), but warned that a paralyzing curariform drug will abolish the signs - dilatation of the pupils, response to pinprick stimuli, etc. - by which the presence of pain is indicated. He adds:

"The widespread success with extracellular or even intracellular recordings from single units in the brain of behaving animals clearly shows curarization is, in certain instances, no longer needed for these delicate and difficult procedures per se."

For just such an experiment, see description of E.V. Evarts' work on p.128,130,131.

The second reference (2) in this editorial directs the reader's attention to an experiment on squirrel monkeys which J.H. Bartlett and the writer of the editorial, Dr. Doty, performed at the Center for Brain Research of the University of Rochester, New York. Describing the technique actually used in the experiment, he says:

"Where it is necessary to stimulate the brain stem of the conscious, immobilized animal, the electrodes should first be implanted and subsequently the alert, freely moving animals should be carefully observed for any evidence of aversive effects, e.g., hypermotility, when stimulation is applied to these electrodes at the intensity to be used in the final experiment (2). With this precaution of stimulating through fixed electrodes with parameters demonstrated by the animal's behavior to be innocuous, the possibility of applying aversive stimuli to an immobilized preparation is precluded."

In spite of his editorial reservations about the use of curariform drugs, Doty apparently felt the monkeys in this experiment had to be paralyzed. Presumably this was to immobilize the eye and eliminate variables in the brain cells' response to light stimuli. The object of the experiment was to study the way electric stimulation of another part of the brain (the mesencephalon) could alter the response of the light-sensitive cells. Although the electrodes penetrated an area whose stimulation in man the investigators admit is "excruciatingly painful," they maintain that the precautions described above protected the animals from discomfort. (Bartlett, J.,1974).

The admission by a neurophysiologist of Doty's stature, confirmed by the editorial in Experimental Neurology, that excruciating suffering may be caused by these techniques unless careful precautions are taken, is certainly disturbing. J. Diner abstracts a series of experiments on animals paralyzed by curariform agents. (Diner,j.,1979,p.45-54). Typically, under general anesthesia, the animal's head is fixed to a stereotaxic instrument, tubes are passed into the windpipe and veins, the skull is opened and an electrode is introduced into the brain, and all wound edges are infiltrated with a local anesthetic. Then the general anesthetic is withdrawn and the animal is paralyzed with the curariform agent. The electrode produces recordings and/or stimulation, sometimes of single nerve cells. Often it is moved around, and it is here that the danger of hitting a pain center occurs.

The precautions described by Bartlett and Doty are not often mentioned by other investigators. Therefore all journals that print reports of experiments using curariform agents should adopt the practice of Experimental Neurology, which states editorially that the following constitutes a requirement for consideration for publication:

"For any experiment in which curariform agents are employed, the necessity for their use must be justified and details provided as to steps taken to reduce or avoid distress to the animal, particularly with regard to electrical stimulation. (Doty, R.,1975, p.iv).



3. DRUGS WHICH RELIEVE PAIN

Since this book is about pain and how it can be relieved, the subject of drugs as pain-relievers naturally comes up for discussion. Below are brief descriptions of the principal drugs and their actions.

Analgesics are drugs used for the relief of pain without causing unconsciousness or sleep - e.g. aspirin; morphine (a narcotic analgesic).

Hypnotics or sedatives are drugs which depress the central nervous system; they do not relieve pain, they dull the conscious perception of it, tending to produce sleep or unconsciousness - e.g. barbiturates.

Tranquilizers alleviate agitation or anxiety, promote muscle relaxation, make pain more bearable, but do not dull mental acuity - e.g. meprobamate ("Miltown"); chlordiazepoxide hydrochloride ("Librium").

Anesthetics are drugs which combine any or all of the above actions, leading to the complete elimination of pain and the induction of unconsciousness - e.g. ether; halothane; barbiturates in large ("anesthetic") doses, or in repeated, smaller doses. The first two are inhalant gases, particularly suitable for long operations since the anesthetic level can be kept constant by altering the inspired concentration; barbiturates are injected, so-called "fixed agents." "Morbidity and mortality in animals are much greater following the fixed rather than the inhalation agents, probably due to the long recovery time, heat loss, pneumonia, etc., aggravated by lack of postoperative care." (Barnes, C.,1973).

Curariform agents are drugs which produce generalized muscular relaxation or paralysis but which have no effect on pain sensibility - e.g. curare; succinylcholine; gallamine triethiodide ("Plaxedil"). When they are appropriately combined with an anesthetic, muscle relaxation is obtained which is desirable in surgical procedures, but there is a risk of causing extreme suffering with curariform drugs, as described on p.20ff., if analgesia is inadequate or absent. That there is real cause for concern is illustrated by the finding that of 110 applicants for grants proposing to use curare in animal experiments, only 7% indicated that it would be accompanied by an anesthetic. These were approved and funded applications made in 1972 and 1976 to either the National Science Foundation or to one of the institutes of the Alcohol, Drug Abuse and Mental Health Administration. (Fox, M.,1979, p.11).


Postoperative Analgesia

In general, the various stages of recovery from an operation proceed in this fashion. The immediate postoperative period, even with the return of consciousness, is usually not pain-filled. Later, if discomfort begins, light analgesia may be tried. Still later, if pain increases, perhaps betrayed after chest surgery by an animal's shallow respiration in an attempt to "splint" the thorax, a stronger narcotic is called for. By this time any respiratory depression caused by drugs used during the operation itself should have worn off, thus reducing the chance of pneumonia. (Rackow, H., 1979).

Barbiturates, often used for animal anesthesia, need special attention, because, as they are metabolized, excreted and as they decline to less than anesthetic levels, they actually increase pain sensitivity. If no postoperative analgesic has been given, an animal may experience considerable pain as the barbiturate concentration in the brain diminishes. The same is true for halothane. (Croft, P.,1964).


Withholding Postoperative Analgesics

During 1973, postoperative analgesics were rarely if ever ordered at New York State Veterinary College at Cornell. (Rubin, N., 1974). No doubt it was the same in other years. Animals there are used for multiple procedures, so the repeated experience of recovery without pain-relief adds up to considerable suffering. In 1966, testifying before a subcommittee of the House Committee on Agriculture, Ralph Mayer stated that during his employment as a technician at the Minneapolis Veterans Administration Hospital no postoperative pain relievers had "ever been given ... to any dog, including the major surgery cases, such as gastrectomies, lung transplants, kidney transplants, bowel anastomoses, open-heart surgery and brain surgery." (US Congress, House of Reps.,1966).

At the same House Hearing, Dr. Donald McQuarrie, Director of Experimental Surgery at the Minneapolis hospital, attempted to defend the withholding of analgesics on the grounds that "narcotics in a dog depress the respiration ... so that pneumonia occurs very frequently, and death is common."

Dr. McQuarrie's comment is surely relative to special circumstances at his hospital. In what condition were the dogs preoperatively? Were they random- source animals, obtained by the hospital from pounds, perhaps already suffering from respiratory disease or anemic from worms? Were his animal-care facilties understaffed, so that postoperative observation was not available to check on the dogs' condition? Were "fixed" rather than inhalation anesthetics preferred by the surgeons, with their greater risk of postoperative complications? Were analgesics given too soon after surgery, before recovery from the anesthetic was well advanced? Was there good rapport with the animals before the operation? Barnes and Eltherington's text comments on this:

"'Making friends' with the animal will contribute much to a smooth anesthetic induction. Attempting to anesthetize a frightened, struggling animal, often made that way by undue restraint, may lead to fatal consequences due to the use of more anesthetic than normally required." (Barnes, C.,1973, p.15).

Although it is probable, for a variety of reasons ranging from the matter of expense to sheer inhumanity, that postoperative analgesics are often withheld from animals when they would have been prescribed for human patients, it would nevertheless be unreasonable to insist on their use in every case. For instance, it has been found that, in a consecutive series of over 1000 human patients who had had general surgical or urological operations, 36% had no need at all for any analgesic drug in the entire postoperative period. (Jaggard, R., 1950). Furthermore, the proportion of patients requiring analgesia postoperatively correlates with the site of the operation, as follows: chest cavity, 74%; upper abdominal, 63%; lower abdominal (excluding gynecological), 51%; limb operations, 27%; inguinal, 23%; body wall, 20%; neck, 12%. (Loan, W.,1967).

Other factors also influence the severity of postoperative pain. They include fear, nausea, drainage tubes, abdominal distension and adequacy of dressings.

These matters must all be weighed by those ordering pain-relieving drugs. Each case is different and there is no simple solution to relief of suffering in animals under experiment. In the operative and postoperative situation there are some fairly precise do's and don'ts, as the above outline suggests. There are less precise indications in nonsurgical cases: for instance, in attempting to relieve the chronic pain of cancer. And unfortunately there are many experiments such as pain, stress, and behavior studies; toxicity tests; safety and potency assays of drugs; addiction studies and investigations of many diseases; in which pain-relieving drugs are withheld on the grounds, sometimes valid but often merely traditional or statutory, that giving them would "defeat the purpose of the experiment." Comments on this will be found throughout the book.

4. THE MOST PAINFUL, DISTRESSING, FEAR-INVOKING EXPERIMENTS

In this book many types of painful experiments are described, some at greater length than others. It is in fact a survey of such experiments throughout the 1970's. For the sake of at least relative completeness, a listing follows of procedures or induced maladies which have been singled out by various authorities as particularly painful, distressing or fear-invoking.

The sources drawn upon variously described these procedures as ones causing "Pain or distress," or "gave concern," or in some cases were "not acceptable," especially if carried out too rigorously or for too long a time or without appropriate pain-relieving drugs. The experiments or illnesses cited inflict a degree of suffering on animals which, depending on the circumstances, ranges all the way from "severe" to the extremity of torture. The authorities include a group of research facilities listing experiments - in their Annual Reports for 1976 under the Animal Welfare Act - which caused pain or distress to animals without the benefit of pain-relieving drugs; a spokesman for the Inspectorate of the British Home Office; Dr. J.R. Baker and a group of British scientists; the Universities Federation for Animal Welfare; the Animal Welfare Foundation of Canada and the Canadian Council on Animal Care; the National Society for Medical Research; the Animal Welfare Institute, as sponsor of Physical and Mental Suffering of Experimental Animals (Diner, J.,1979), and Dr. Alice Heim, recently Chairman of the Psychology Section of the British Association for the Advancement of Science. These groups represent either research-associated scientific bodies or animal welfare organizations identified with a reformist rather than an anti-vivisectionist position; thus their selection of experiments as ones which often lead to undue suffering is particularly significant.

The experiments are listed alphabetically; the reference numbers refer to the above-mentioned authorities (cf. key on
p.30); the letters "AP" identify citations in this book (cf. Index) .

Anaphylactic shock. 4; AP.

Aggression, induced (often by electric shock - resulting in fighting, wounding, killing). 2, 9; AP.

Blinding. 9; AP.

Brain stimulation, electrical, painful. 6, 7, 9; AP.

Burns. 2; AP.

Cancer, chronic. 1, 2, 7; AP.

Cannula, chronically implanted. 5; AP.

Cold, prolonged exposure to. 2, 7; AP.

Coronary constriction, induced. 9; AP.

Defense research (radiation, ritants, fire, explosives, etc.). 7; AP.

Drowning, following swimming toexhaustion. 7, 8; AP.

Drug addiction (withdrawal symptoms) 8.

Fear ("conditioned emotional reaction."). 8, 9; AP.

Fractures. 2.

Grooming disruption. 9; AP.

Heat, prolonged exposure to. 2.

Heart failure, stress induced. 9; AP.

Helplessness, learned (usually via electric shock). 8; AP.

Infectious disease, chronic. 2, 7; AP.

Inhalants, toxic. 5; AP.

Irritants, corrosive, of digestive tract. 4, 9; AP.

Irritants, eye.1, 4, 5, 9; AP.

Irritants, joint (injected) 4, 5; AP.

Irritants, skin. 4, 5; AP.

Isolation, social, or from mother.8, 9; AP.

Electric shock, painful. 6, 9; AP.

Pain, postoperative, unrelieved. 2, 7; AP.

Pain research. 9; AP.

Pain, unrelieved, combined with curariform paralysis. 2, 7, 9; AP.

Pathogens (Rabies, Tetanus, etc.), virulence challenge. 4; AP.

Punishment (usually electric shock) in behavior conditioning. 5; AP.

Radiation sickness. 1, 9; AP.

Repeated use of same animal (especially in painful brain exploration). 7; AP.

Restraint, physical, prolonged. 2, 7; AP.

Seizures, convulsive, induced by chemical or electrical brain stimulation. 9.

Sleep deprivation, prolonged. 8.

Sound, loud, prolonged exposure to. 2, 9.

Starvation, prolonged. 2; AP.

Stress. 6, 9; AP.

Thirst, prolonged. 2; AP.

Tooth-pulp stimulation, painful. 4, 9; AP.

Toxicity Testing, in general. 2, 4, 5, 7; AP.

Toxicity Testing, lethal dose ("LD/50") 5; AP.

Toxicity Testing, metal poisoning. 7; AP.

Toxicity Testing, rodenticides. 6.

Trauma (battering in drum; crushing, striking) without pain relief. 2, 3, 9; AP.

Ulcers, gastric, stress induced. 8; AP.




REFERENCES


1. U.K. Home Office, 1974.

2. Canadian Council on Animal Care, 1978.

3. Baker, J., 1949.

4. USDA/APHIS, 1976.

5. Anon., 1975.

6. Universities Federation for Animal Welfare, 1963.

7. Hughes, T., 1976

8. Heim, A., 1978.

9. Diner, J., 1979.


NOTES:

1. These comments refer to vertebrates, but invertebrates exhibit defensive movements which suggest that they experience pain. Some, like the octopus, have a highly developed nervous system. The degrees of consciousness among the more primitive organisms are unknown, but anesthetics have been developed and should be used at least for all multicellular forms of macroscopic dimensions. (Kaplan, J.,1969).
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2. Nashold et al. probed pain centers in the brains of conscious patients, but only as long as the latter would endure it. (cf. p.19-20).
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