Herpes zoster, or zona, is a common nervous disease known since ancient times but still possessing many enigmatic features. From the contributions of von Bärensprung,1Head and Campbell,2Lhermitte and Nicolas3and many others the broad outlines of this condition may be sketched. The present day conception of herpes zoster embraces the following assumptions and facts: The disease is probably due to a filtrable virus, similar to, if not identical with, that of varicella, which provokes an acute inflammatory reaction in isolated spinal or cranial sensory ganglia, the posterior gray matter of the spinal cord and the adjacent leptomeninges. The clinical manifestations are a vesicular cutaneous eruption, radicular neuralgia and, less often, segmental palsies and sensory loss. The association of the cutaneous eruption with a disease of the peripheral nerves was brilliantly deduced from clinical data by von Bärensprung1ain 1861, and in 1862 he described