English: This is a heat exchange between vessels as one vessel gives heat and the other receives it. When part of a mammals body, in this case a duck foot, is submerged in a colder substance, in this case being water, the mammal starts counter current heat exchange. The vessel going down transfers it's own heat to the vessel that has lost heat.
1 - This is the outside of the ducks foot.
2a - Warm blood is flowing from the core of the body down the vein.
2b - The blood flowing up from the cold substance is receiving heat from the vein.
3 - The transfer of heat form the vein to the vessel.
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