SHEILA Brennan's claims (Letters, July 18) that animal experiments are useless, misleading, cruel, and that there are alternatives, are simply wrong.

Those involved in animal research care just as much about animals as anyone else. For this reason, and because there are very strict controls, animals are only used in research when absolutely necessary.

The so-called alternatives to animals - tissue culture, computer modelling etc - are actually used much more than animal studies, but alongside them, not instead of them.

It is wishful thinking to believe that these methods could replace the use of animals on any large scale. We only get part of the picture by studying molecules, cells, tissues or isolated organs. To begin to see the whole picture we need to look at the complex interactions that take place in whole living animals.

It would be impossible, for instance, to measure blood pressure in a test tube, or develop new intensive care techniques using a computer. With present day technology, and even in the foreseeable future, this is simply not possible.

Animals do not provide perfect models for human diseases, but they are still the best we have. It is a fact that most major medical advances have depended crucially on animal studies - vaccines, antibiotics, insulin for diabetes and kidney transplants are just a few examples.

We still face many unsolved medical problems such as AIDS, Alzheimer's disease, motor neurone disease and cystic fibrosis. Medical research must use all appropriate methods, including a small proportion of humane animal experiments, in the struggle to conquer these diseases.

BARBARA DAVIES, Deputy Director, Research Defence Society, Great Marlborough Street, London.

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