An upper limit to the number of sodium channels in nerve membrane?

Abstract
A small volume of artificial sea water containing 300 nM tetrodotoxin (TTX) was applied successively to seven lobster nerve trunks and the cumulative uptake of toxin investigated by bio-assay. Light and electron microscopy indicated that the nerve trunks had a total axonal area of 0.7 x 104 cm2/g. Sodium analysis gave a sodium space for the nerve trunks of 30%. The. amount of toxin taken by up the cells in 1 g of nerve is less than 6 x 10-11 moles. There are probably fewer than 13 sodium channels/[mu]2 axon in lobster nerve.