The picture of the “mouse with the ear” surfaces again in the wrong context (TES Extra RE, December 6). This startling image has embedded itself in the public mind as an example of “genetic engineering”, which it is not.

The mouse is an example of experiments on animals - an ear shape has been grown in culture using human cartilage cells. The cartilage matrix thus formed is implanted under the skin of people with missing or damaged ears. It is important to test that an implant does not cause unexpected tissue reactions. This test was performed by inserting the cartilage under the skin of a mouse. The resulting data enabled medical researchers to make the best possible estimate of the safety of the technique before applying it to people.

The issue of animals used for medical research is contentious, and arouses much interest from pupils and teachers. Science teachers who would like further information about this would be welcome to visit our stand at the forthcoming ASE meeting in Birmingham January. Teachers from other disciplines are welcome to contact me at the address below.

By the way, the current alternative to an implanted ear is a foam-rubber ear. The NHS permits the supply of two foam-rubber ears, and a bottle of spirit gum, each year, to people in this unfortunate position. I know which of the alternatives I would prefer.

SIMON BROPHY Director Biomedical Research Education Trust, Suite 501, International House, 223 Regent Street, London W1.