Human reaction and animal reaction – that is the question

By Prof Pietro Croce †

All living organisms – from bacteria to human beings – have certain similiarities. For everything that lives on Earth has certain chemical elements and biochemical compounds in common in its physical make-up. But simply combining chemical substances does not create an organism or a living being. An organism is not defined solely by the organisational combination and effect of the countless assortment of molecules, substances and tissues; also required is the interaction between them, so far not explained scientifically and incapable of being reproduced, which has to have both meaning and purpose. This is commonly described as the organism's physiology, or as Life.

The more complex a living being is, the more incomparable it becomes with other living beings. Man is considered to be the most highly developed organism on Earth. Certain elementary physiological functions and biochemical reactions also certainly exist in the animal world. The overall purpose-designed organisation and the respective functions of a human being are, however, often entirely different from those of an animal, and a large part of the psychological effects and emotional and mental control – as well as additional undefined external influences – cannot be ascertained; in fact, they have not yet even been defined. The problem lies in the fact that one cannot conclude from observing the individual reaction of an animal organism that a human being will react in the same way. We only learn whether a human will react similarly to an animal once we are able to compare the results of the same experiment on a human being. The differences in effects and tolerability are frequently considerable, and the effects often just the opposite, which means that to apply the results of animal experiments to the human situation amounts to an absolutely incalculable risk.

Furthermore, the practice of 'animal research' impedes the discovery of important scientific knowledge. We cannot, for instance, avoid facts deduced from animal experiments being assumed to be important although they are in fact irrelevant, and truly important facts being rejected, or not followed up, because they do not produce results in the animal laboratory.

The following examples from widely different fields will serve to make this clear, and could be added to ad infinitum:

Human beings and animals: they could not be more different

• The amanita toadstall, deadly to humans due to its various toxins, does no harm to rabbits, hares and various rodents. Ruminant animals are also quite resistant to its poison.
• Lemon juice, a valuable part of our human diet with its beneficial effects on our digestion, is highly poisonous for cats.
• Parsley, which humans find so tasty and digestible, is deadly for parrots – although not for all breeds.
• Prussic acid (also known as cyanide) is so poisonous to humans that they can die simply by inhaling its fumes. But sheep, toads, porcupines and other animal species can tolerate large quantities of this poison without any problem.
• Morphine has a calming effect on human beings and dogs, promoting sleep and easing pain. However, high doses of it send cats into an uncontrollable frenzy of excitement.
• Penicillin is known as a relatively well tolerated medicine, very effective against infections. Guinea-pigs and hamsters can die from it.
• The porcupine can tolerate without any reaction a quantity of opium that would be lethal to a human being.
• Botulintoxin, which can develop in canned foods and is highly poisonous for consumers, has hardly any toxic effect on cats. For mice, however, it is one of the most rapidly lethal poisons.
• Methyl alcohol has caused blindness in thousands of humans, but has no harmful effects on the most commonly used laboratory animals and produces no reaction in their eyes. 
• Arsenic, highly poisonous for human beings, is tolerated in large quantities by sheep and other ruminants, with no ill-effect.
• A deficiency of vitamin C in the diet leads to death from scurvy in humans, most primates and guinea-pigs. Dogs, cats, hamsters, rats, mice and many other animals can produce the vitamin in their own bodies, and live out their entire lives without any vitamin C being included in their diet.
• One hundred milligrams of scopolamine is harmless to dogs and cats; yet just five (5!) milligrams are enough to kill a human being. Relative to weight, therefore, these animals tolerate four hundred times the dose that is lethal to humans.
• Strychnine is harmless to guinea-pigs, chickens and monkeys in amounts that would cause severe convulsions to an entire human family and probably kill every member of it.
• Hemlock, so well-known through the death of the famous Socrates, is eaten by horses, mice, goats and sheep without any ill-effects.
• Chloroform, used for many years in surgery as a narcotic for humans, is a deadly poison for dogs.
• Insulin causes deformities in rabbits, chickens and mice, but no such effects have so far been observed in humans.
• Cortisone likewise causes deformities in mice and other rodents, but clearly not in human beings. Cortisone precipitates birth in sheep and cattle, a side-effect not observed in humans.
• Regardless of its negative effects on blood formation, Novalgin relieves pain in human beings. In cats and various other animal species it causes irritability and aggressiveness, accompanied by pronounced salivation.
• The anti-inflammation drug phenylbutazone can be administered to dogs, pigs, horses and monkeys in high doses over long periods, because it is rapidly broken down in their bodies. In human beings, not only does it take 200 times longer for it to lose its toxic effect, it also accumulates in the body.
• The antibiotic chloramphenicol damages the blood-forming bone marrow of human beings and the hearing ability of their inner ear, but this is not the case with the most commonly used laboratory animals. Chloramphenicol can lead to circulatory collapse in new-born humans, but does not produce this effect in domestic and working animals.
• Mice, rats, rabbits and pigeons are largely insensitive to the atropine present in deadly nightshade and other species of solanum, because the enzyme atropinesterase enables these animals to break down this substance in their organisms. In the human body, dependent on the dose, atropine leads to severe symptoms of poisoning such as speech disturbances, fever, confusion, hallucination and coma.
• Methyl fluoracetate is poisonous for all mammals, including humans. Mice, however, can tolerate doses 50 times higher than the level that kills a dog. What dose can a human being tolerate – the same as a mouse or a dog? 
• Today, there are some 15 medical substances available for the treatment of people suffering from epilepsy. Of these, only potassium bromide and phenobarbital can be used to treat epilepsy in dogs; the others are rendered inactive very rapidly in dogs, induce fits instead of preventing them, cause liver damage, microscopic holes in the brain or other massive problems.

Humans are not all the same

One therefore only needs to know which animal species to experiment upon in order to obtain a result that is white or black, high or low, good or bad, harmless or dangerous. It is equally obvious, however, that experimenting on an animal can provide no evidence as to the reaction and safety of an unknown substance when administered to a human being.

But even individual human beings show considerable differences with regard to their origins and genetic make-up, and for this reason they also react very differently to external stimuli:

• Approximately 10% of people of Caucasian origin are unable to tolerate milk sugar ( lactose) beyond the age of about 22, even though they have hitherto eaten it with great pleasure. This does not mean that they are ill – they are simply different in their reactions from the other 90% of the human race. 
• 65% of humans find that phenylthiourea (PCT) tastes bitter; for the remaining 35% it is tasteless.
• Most people do not eliminate beta-amino-isobutyric acid in their urine, but some 8% of people do so.
• Human blood contains at least 17 types of transferrins (the proteins which transport iron), but the proportions vary widely from person to person.
• 52% of the proteins in blood serum comprise albumin, but some individuals have two types of it: A1 and A2. 

Infections: sometimes lethal, sometimes harmless

Most of the known animal species do not fall victim to the most common human ailments. So how can the effectiveness of a medicine for a specific human disease be assessed? As the animal does not catch this disease, the disease is created in it artificially in the animal laboratory. This might seem relatively simple in respect of infectious diseases, but the reality is that it is full of imponderables and dangers, because animals react differently than humans to the same infection:

• The smallpox virus and yellow fever virus do not cause illness or any infection reaction in any known animal.
• The rabbit is very vulnerable to the causative agent of tuberculosis in cattle, but hardy susceptible at all to that of human tuberculosis. The situation is exactly the opposite in the guinea-pig. But in neither the guinea-pig nor the rabbit does the disease follow the same course as in human beings.
• The causative agent of cattle tuberculosis is relatively harmless to humans, and was therefore used for a long time as a vaccine. In the hamster, on the other hand, it causes a serious infection that results in death. In any other species?
• The mycobacterium leprae, responsible for leprosy, develops - apart from in man – in only one animal species, the armadillo. But even in that animal it does not develop spontaneously; only in the animal laboratory.
• The treponema pallidum bacterium causes syphilis only in human beings. When transmitted artificially to monkeys, it brings about an acute illness which follows a quite different course, and takes quite different forms, than in humans.
• The actinomyces bacterium results in a form of skin disease in cattle. In humans, it causes an inflammatory infectious disease of the internal organs which often proves fatal. It is hardly possible to infect any laboratory animal with this bacterium.

Cancer victim or top fit

I have provided above a few examples of the differences between human beings and animals with regard to infectious diseases. The animal experimenter is convinced that, by deliberately transmitting the causative agent to an 'animal model' in the laboratory, he can simulate a human disease and then work out therapeutic methods to cure it. In a similar way, by means of injecting cancer cells into an animal or transferring them on to it, attempts are made to discover how this deadly illness comes about. But in this case the differences between humans and animals are even greater, and an inextricable tangle of inconsistencies and contradictions becomes apparent. A cancer-causing substance can produce different effects and results not only in humans and animals, but also in different strains of the same species:

• It is fortunate that the epilepsy drug phenobarbital was not tested a century ago, because it causes liver cancer in rodents although certainly not in humans.
• Urethane causes cancer in the spleen, lymph nodes, lungs and other organs of the mouse strain CHF. In the mouse strain CBI it produces malignant lymph tumours. In man, it has been used as a medicine against leukaemia.
• Dimethyl-benzo-anthracene causes lymphomas in mice of the so-called „Swiss“ strain, but bronchial adenomas in the „Strong A“ strain of mice and liver cancer in other strains – but only in the males!
• Carbon tetrachloride leads to liver cancer in mice, but in rats it causes cirrhosis of the liver.
• Chloroform causes liver cancer in some strains of mice – but only in females, not in males.
• INH (isonicotinic acid hydrazide) causes bronchial cancer in some strains of mice. No similar reaction has so far been observed in human beings, even though enormous quantities of this substance have been used for decades in the treatment of tuberculosis.

Conclusion:

These few examples, of which there are very many more, serve to show that no substance is fundamentally poisonous: any substance only poisons certain species of animal (or only in certain doses). With animal experiments one can therefore prove, or disprove, whatever one wishes. So long as the right animal species is chosen, a medicine can be described as harmless or poisonous, effective or ineffective, according to whatever one wants. Animal experimentation is therefore an unscientific method, a methodological error. And any Science that is based on false methodology can only be bad Science. Our purpose is to put an end to this error.

Extract from the book ´Vivisektion oder Wissenschaft – Eine Wahl` (´Vivisection or Science – a choice to make`) by Prof. Dr. Pietro Croce, Milan, 1988, Buchverlag Civis.

The author

Prof. Dr. Pietro Croce studied and graduated in medicine at the University of Pisa, Italy, and did research work at the University of Colorado in Denver, USA and the University of Toledo, Ohio, USA. 1952-1982: head of the laboratory of clinical chemical analysis, microbiology and pathological anatomy at the L. Sacco Hospital in Milan, Italy. Visiting lecturer at the University of Milan. Author of several books, including "Vivisection or Science – a choice to make". He performed animal experiments himself for 20 years, until he recognised their unscientific nature in the early nineteen-eighties and then campaigned tirelessly against the vivisection system until his death in 2006.