THE report by Cogan1 of the syndrome of nonsyphilitic interstitial keratitis and vestibuloauditory symptoms, in which the matter of etiology was permitted to remain unsolved, has stimulated interest in this subject. Because of the rarity of diagnosis of this syndrome and because of a suggested etiologic factor in the case to be reported, this paper is submitted as an introductory study of postvaccinial encephalitis. REPORT OF A CASE A man aged 30, who had served in the armed forces for slightly over four years, had onset of the acute episode of his illness on March 13, 1945, one hour after the noonday meal, which consisted of pork, vegetables, bread, butter, coffee and canned fruit. The initial symptom was nausea, which was followed shortly by retching and then by vomiting of projectile character. After the vomiting had ceased, the patient noticed a persistent dull nuchal ache, which did not keep