Sheets of human skin, grown from skin cells of volunteers, are living in dishes at the University of Michigan as part of a search for toxicity-testing methods that require no laboratory animals.

The Michigan experiment will determine how human skin reacts when in contact with potential toxins in cosmetics, detergents, industrial chemicals and other substances. Most testing is now done on rabbits, mice, pigs and other animals.

In the past, skin tissue cultures have been submerged in nutrient fluids that interfere with the action of the substance being tested. Michigan scientists Frizell Vaughan and Isidore A. Bernstein have found a way to make the cells proliferate and form a sheet, about an inch across, with its upper surface exposed to the air.

As a result, the epidermal cells, progeny of a few shaved from the skin of a volunteer, can form a more natural skin with living cells underneath and dead cells on top. It is the layer of tough, dead outer cells in human skin that protects the body from toxins and microbes in the outside world.

Although skin cultures cannot entirely replace testing on living animals, Vaughan and Bernstein say that they expect them to prove useful in telling which chemicals are able to penetrate the epidermis and reach the bloodstream.

The skin cultures can also be used for studies of wound healing.