Cocaine diffuses through the epineurium with remarkable rapidity. The coefficient of diffusion of cocaine in the epineurium cannot be less than 0.44 x 10–4 cm.2/min.; it probably is not less than 1.22 x 10–4 cm.2/min.
Lack of sodium markedly sensitizes the nerve fibers to the anesthetic action of cocaine.
With sodium-deficient A fibers the action of cocaine develops in two phases. During the first phase cocaine substitutes for sodium and restores to A fibers the ability to conduct impulses; during the second phase cocaine produces anesthesia.
It is suggested that cocaine anesthetizes the nerve fibers through the sodium mechanism; i.e., by interfering with some of those chemical reactions in which, directly or indirectly, the internal sodium takes part.