The key method that Warburg had pioneered was to measure the escape of gases from thin slices of tissue, cut using a razor blade. When practised skilfully, the slice was thin enough for oxygen to penetrate fully by diffusion, while the cells in the centre of the slice were undamaged, functioning more or less normally. The slices were then placed in a solution with a similar composition to blood plasma, in a glass flask joined to a manometer (which measures gas pressure like a barometer) and sealed tight. Under these conditions, gases could bubble out of the tissue slice, which would increase
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