It acts as a countercurrent heat exchanger, cooling blood in adjacent arteries. Rete mirabile function as countercurrent heat exchangers that prevent metabolic heat loss at the gills. VV ECMO trials are performed by eliminating all countercurrent sweep gas through the oxygenator. Seabirds distill seawater using countercurrent exchange in a gland with a rete mirabile. Diffusion between these opposing flows increases the separation by the principle of countercurrent multiplication. A countercurrent exchange system is utilized between the venous and arterial capillaries. In countercurrent flow, the two flows move in opposite directions. Inducing a countercurrent flow uses countercurrent multiplication to enhance the separative effect. Complete separation is effected by using a countercurrent exchange method. In industrial applications the liquid and vapor streams can have co-current or countercurrent flows. The blast furnace operates as a countercurrent exchange process whereas a bloomery does not. The medullary cones function as countercurrent units that achieve the production of hyperosmotic urine. The device's looping channels strives to simulate the countercurrent mechanism of the loop of Henle. A countercurrent heat exchange with forced cooling air does the job. Complete separation can be achieved continuously by use of countercurrent exchange methods.