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concentrations, rise, while its oxygen, sodium ion, adenosine triphosphate, phosphocreatine,concentrations go down. These changes affect much of the tissue metabolism. It is hoped andnormally assumed that they will reverse during incubation. There is no realistic way of testingthis, since the volume and chemistry of the tissue changes during incubation. In thiscircumstance, it is worth asking whether cell biologists should use tissues in vitro at all. Perhaps,they should confine their experiments to working on intact animals and human beings, tissuecultures, unicellular organisms and plants.Teasing tissue breaks connections and also separates compartments which were formerlyadjacent. However, it is extremely unlikely that separating parts of cells, which were previouslyadherent to each other, would not affect the permeability of their membranes. Nevertheless, thequantity of energy injected into tissues by homogenisation and centrifugation is likely to beorders of magnitude greater than is used in teasing or micromanipulation.Microscopy of cells subjects them to a great deal of light energy, much of which isdissipated in the structures in focus. This may break down volatile compounds, and also cause oraccelerate intracellular chemical reactions. Photography is an important aid to microscopy, but,nowadays, electronics is often used to enhance micrographs, to highlight features, and toeliminate imperfections believed to be artefacts, etc. Electronic circuits 'improve' micrographs,but it would be useful if microscopists and bio-ethicists would discuss this practice to clarify itsmorality.6