Epidemic encephalitis, also known as lethargic encephalitis, nona, infectious ophthalmoplegia and by various other designations, has only recently sprung into prominence but by reason of its rapid spread over the greater part of both hemispheres in less than two years, it has engrossed to an unparalleled degree the attention of scientists throughout the world. Although von Economo's first description of this disease only dates back to the spring of 1917 the amount of literature concerning it has already reached incredible proportions, a fact which has served promptly to vulgarize the symptomatology and diagnostic features of this newly isolated affection and also to provide us with a preliminary knowledge of the character and distribution of the underlying histologic changes.
It seems well established that the lesions involve with especial predilection the tegmentum of the pontopeduncular region and the basal ganglions, and give rise clinically, in the majority of cases, to a