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Toluidine-blue-stained sections showing the complex meshwork formed by the air capillaries (AC) and the blood capillaries containing red blood cells. Arrows, extravasated erthrocytes lying in the ACs; stars, sites where the ACs connect openly or through narrow channels. It is evidently difficult to infer the 3D shape of the ACs from sectional profiles. Scale bars, 10 μm.
