Countercurrent Heat Exchange in Arctic Legs

Arctic foxes, reindeer, and wading birds keep their core warm on ice by running the artery and vein of each limb side by side, so heat leaks continuously from outbound warm arterial blood into inbound cool venous blood along the whole length of the limb. This chart solves that real countercurrent heat-exchanger balance along the limb's length, plotting artery and vein temperature from body core to extremity as you tune blood flow, vessel contact efficiency, ambient cold, and insulation — and lets you switch the exchange off to see the real, dramatic jump in heat loss without it. Drag to pan, scroll to zoom, and click either curve to read its local temperature.