All eight experiments summarised below are currently being used around the world and four of them - numbers 1, 3, 4 and 7 - were carried out recently in British laboratories. The other four were done in other countries and almost certainly would not be allowed here. But how is the line drawn?
1 Rabbits have an eye infected with herpes to study the effect of a new anti-viral drug. The eyes become "grossly inflamed, with injection of the conjunctiva, purulent discharge, opacity of the cornea and extensive ulceration."
2 Rats are tumbled in a rotating drum to produce in them a condition equivalent to the traumatic shock that people experience after a severe accident.
3 Yeast is injected into the paws of rats to cause inflammation. When pressure is applied, the rats respond with "shrill vocalisation" and "strong attempts to withdraw the paw." New pain-killing drugs are evaluated by their effect on this response.
4 The tooth pulp of dogs is stimulated electrically to cause pain in another experiment also used to test pain-killing drugs.
5 Young monkeys are isolated in conical containers known as "pits of despair" until they develop a condition akin to that sometimes found in human infants separated from their mothers.
6 Dogs are given repeated electric shocks from which they are unable to escape until they give up trying, a psychological condition known as conditioned helplessness, used to study acute depression in humans.
7 Rats have a leg bone broken with dental pliers under anaesthesia. After coming round, the rats are used to test the effects of an anti-inflammatory agent over a period of six days.
8 Dogs are infused continuously with substances which are known to cause pain when released naturally in the body - after physical injury, for example.
More than four million animal experiments are carried out annually in Britain. Two facts are fundamental to the debate about them. First: without animal experiments much medical and biological research would grind to a halt. Second: some experiments do cause suffering.
The 1876 Cruelty to Animals Act recognises the first and tries to minimise the effects of the second by prohibiting "severe pain which is likely to endure."
But inevitably this results in messy compromises - ones that the increasingly militant animal liberation movement find utterly unacceptable.
Different elements in the movement are prepared to take different actions to make their point. Most extreme are the letter-bombers of the Animal Rights Militia. Then there are the guerrillas of the Animal Liberation Front who risk prison for their break-ins into animal laboratories; the activists who recently took over the British Union for the Abolition of Vivisection (BUAV) who protest via civil disobedience - as does Animal Aid; the street campaigners of the National anti-Vivisection Society: and - most willing to accept compromises - The RSPCA.
"You can do medical research without animals," says Angela Walder of the BUAV. "Why do millions of experiments on cancer when we already know how to prevent the commonest form? The link between lung cancer and cigarettes was discovered without animals."
But the fact remains that huge areas of medical research would be impossible if all animal experiments were banned. Most research on the nature of, and cures for, cancer would be impossible. Work on organ transplantation and other forms of experimental surgery would cease. Above all there would be no new drugs.
"The last 20 years or so," says Sir William Paton, professor of pharmacology at Oxford and former chairman of the Research Defence Society, "have seen the development of polio vaccines, drugs for high blood pressure, anti-depressants, allopurinol for gout, the cephalosporin antibiotics, effective drugs for peptic ulcers, immunosuppressants for transplant surgery and the first useful anti-virals. Without animal experiments we would have had none of these."
Brigid Brophy the novelist, a campaigner for total abolition of animal experiments, faces this issue squarely. "The loss that might result is a loss humanity would have to bear," she says. We would not, she points out, experiment on 10 children to find a cure for a disease that would save the lives of a thousand. "If we abandoned experiments on other animals we might have to bear more losses of that kind. But I think the scientists could come up with alternatives."
But how many people would accept the death of a single child if animal experiments could save it?
The statistics of animal experimentation in Britain are set out in a booklet published annually by the Home Office. The most recent issue shows that in 1981 there was a grand total of 4,344,843 experiments. They include everything from trials of new pet foods involving no suffering whatsoever to experiments near the borderline like the examples described above.
(It should be noted that the examples are not widespread. They come from a list of experiments that the Animal Experimentation Research Department of the RSPCA regard as questionable).
The total number of experiments has declined in recent years from a peak of over 5.5 million in 1971. Tighter research budgets, mounting costs of drug development and general hostility to animal experiments have played a part. On the other hand, the increasingly elaborate safety testing required for drugs tends to keep the total high.
Over 75 per cent of the animals used were mice or rats. Over half the experiments were concerned with development of drugs and similar products. About 20 per cent involved use of anaesthetics. All "vivisection" experiments come into this group.
Control of experiments is the responsibility of a team of 15 Home Office inspectors, all doctors or vets, who visit laboratories regularly without warning. They have to approve all premises and license individual scientists. At the last count 527 premises were registered. Most are academic institutions, but most experiments are carried out by commercial organisations.
The inspectors also vet most experiments in advance. If they do not like the look of one, they may suggest modifications or reject it completely. Controversial cases may be referred to the Advisory Committee on Animal Experiments. All experiments require a special certificate unless they are carried out under anaesthaesia and the animals are killed before they come round. No operative procedure more complicated than inoculation or taking a blood sample from a vein may be performed without an anaesthetic.
But as the examples quoted at the beginning of this article show, some permitted experiments do cause suffering. Just how many is difficult to estimate from the statistics but there must be some chance of suffering in the 17 per cent of experiments in which animals are anaesthetised and then allowed to recover, and in acute toxicity testing when some animals are poisoned to death.
The 1876 Act includes an absolute prohibition on severe and enduring pain, and inspectors can order the immediate killing of any animal they think is suffering in this way. But even moderates in the animal rights movement are not happy with the so-called "pain condition".
"What do 'severe' and 'enduring' mean in practice?" asked Dr Judith Hampson of the RSPCA.
"It is mainly a matter of humanity and common sense," says Mr Michael Richards, the chief Home Office inspector, "though we always interpret the pain condition liberally from the animals point of view."
But once a certificate has been issued it is left to the experimenters to judge whether their animals are suffering severe and enduring pain. The number who would be prepared to sacrifice perhaps months of work in the interests of their animals is anybody's guess, but those without active consciences have a lot to lose by failing to follow the spirit of the Act. Anyone breaching it risks losing the licence to experiment on which his livelihood may depend. His colleagues will be against him in case the laboratory loses its registration and they lose their livelihoods too. And moast labs have large enough staffs to include people prepared to report transgressions.
But for the animal welfare campaigners the controls are not tight enough. If they cannot get a total ban on animal experiments they at least want reforms. After the appearance next month of a European Convention on animal experiments they may get some.
One contentious issue is "useless" experiments of little scientific merit of practical value. Scientists would fight hard to prevent a definition of useful or painful being written into any new legislation. "It is not possible to define nasty experiments without including some that should be done," says Professor Sam Shuster of Newcastle University, "and you can't legislate stupidity out of the laboratory any more than you can legislate it out of the legislature." However, there is wide support for some kind of advance refereeing system in which other scientists expert in the field would have to endorse any proposed animal experiment.
One area where there is wide agreement on the need for reform is in the statutory safety testing of drugs, pesticides and the like. "At least half the statutory tests on drugs cold be dropped without affecting safety" says Shuster. "They just aren't productive. Thousands of animals are sacrificed for a negligible gain."
The so called LD50 test is a notorious example. The initials stand for "lethal density" and the test is an estimate of the amount of a substance that will kill 50 per cent of a batch of animals. It is required by law for drugs, pesticides, and food additives; and it can be useful. But if, say, it is safe to consume a thousand times more of a food additive than anyone is actually likely to insure, what is the point in knowing that a million times that amount is the LD50 for rats? A "limit test" to establish that there is an adequate safety margin would do just as well and might not, harm any animals at all.
Around 10 per cent of animals experiments are LD50 and other tests of acute toxity. Not all the animals die, but substantial numbers do, often unpleasantly.
However LD50 are enshrined in numerous regulations, and getting rid of them will be a slow business even if everyone agreed.
Then there is the problem of similar regulations overseas. The British pharmaceutical industry exports รบ600 million worth of drugs annually. If an importing country requires an LD50 test it has to be done somewhere. There is little point in saving British rats if it means that Ruritanian rats are sacrificed instead.
The whole field of safety testing cries out for international action. With world-wide harmonisation, and acceptance of one country's tests by an other, vast numbers of animals (and money) could be saved.
Another much canvassed possibility is the use of tissue cultures, and simple life forms instead of whole animals in the laboratory.
But such tests have highly limited validity and it is extremely unlikely that there will ever be a total escape from the stark choice between human suffering and animal rights.
