The Squid Giant Axon

The experimental arrangement diagrammed in Figure 7-1 was technically feasible only because nature provided neurophysiology with an axon large enough to allow experimenters to thread a pair of wires down the inside. The axon used by Hodgkin and Huxley was the giant axon from the nerve cord of the squid. This axon can be up to 1 mm in diameter, large enough to be dissected free from the surrounding nerve fibers and subjected to the voltage-clamp procedure described above. The axon is so large that it is possible to squeeze the normal ICF out of the fiber like toothpaste out of a tube and replace it with artificial ICF of the experimenter's concoction. This allows the tremendous experimental advantage of being able to control the compositions ofboth the intracellular and the extracellular fluids.

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