This section will concentrate on one example of a discursive essay. Read the essay over carefully. Study it and work out how it has been written.
A rabbit and a rodent in a scientific laboratory
1 A subject which always arouses strong feelings on both sides of the argument is the use of animals in medical research. I believe that, though this may have been necessary in the past, other ways can be developed to test drugs and, in the future, animals should not be used.
2 One of my main reasons for saying this is that living tissues can be grown in test tubes and new drugs can be tested on these. Computers can also be programmed to show how medicines will react in the human body.
3 Moreover, animals are not always like humans. They do not suffer from all human diseases, so scientists have to give them the illnesses artificially. The joints in rabbit legs are inflamed with chemicals to help research in rheumatism. These tests do not always work because animals do not react to drugs in the same way as humans. Aspirin, for example, damages pregnant mice and dogs, but not pregnant women. Arsenic, which is a deadly poison for humans, has no effect on sheep, while penicillin, which is so valuable to humans, kills guinea pigs.
4 In addition, I believe that animal experiments should not be used because of the unnecessary pain that they cause to animals. The government introduced new rules about the use of animals in experiments in 1986. Scientists claim that these rules safeguard animals because they state that discomfort must be kept to a minimum and that painkillers must be used where necessary and appropriate. Surely this means, however, that scientists can still decide not to use painkillers in the animal experiments because they do not consider them appropriate. The British Union against Vivisection claims that 75% of animals experimented on are given no anaesthetic.
5 In spite of the claims of some scientists about the effectiveness of animal research, the death rate in this country has stayed the same over the last thirty years. There is also more long-term sickness, even though greater numbers of animals are being used in research.
6 On the other hand, scientists claim that some experiments are so small, for example giving an injection, that painkillers are not needed. They also argue that experiments on animals have been very useful in the past. For instance, the lives of ten million human diabetics have been saved because of experiments with insulin on dogs. Dogs also benefited, as the same drug can be used on them. In fact, a third of medicines used by vets are the same as those used by doctors.
7 It is argued by researchers that the use of animals in experiments cannot be replaced by methods using living tissue which has been grown in test tubes. These tests do not show how the drugs work on whole animals and so they only have limited effectiveness.
8 Although I accept that some drugs can be used on animals and humans, this does not mean that they have to be tested on animals in the first place when alternative methods are available. Alternative methods do work. Various groups have been set up to put money into other ways of researching. For example the Dr. Hadwen Trust has shown how human cartilage can be grown in test tubes to study rheumatism. Similar research is being done into cancer and multiple sclerosis. Tests can be done on bacteria to see whether a chemical will cause cancer. There is even a programme of volunteer human researchers, where people suffering from illnesses offer to help in research.
9 In conclusion, I accept that animal experiments have brought great benefits in the past, but now money needs to be spent on developing other methods of testing drugs and medical procedures, so that the use of animals can be phased out altogether.