The reappearance of cases of epidemic encephalitis in Europe and America in the last few months has served to emphasize the sinister character, as well as our imperfect knowledge, of the disease. Moreover, it has served to remind us of the notable fact that within a period of about twenty years, several epidemic diseases having their chief seat of injury in the central nervous organs have prevailed widely in America and in other parts of the world.
Indeed, the two decades of the new century have witnessed destructive outbreaks of epidemic meningitis, epidemic poliomyelitis, and latterly epidemic encephalitis. This list does not include an epidemic disease presenting peculiar features which arose in 1917 and 1918 in New South Wales, Queensland and Victoria. According to different reporters, this malady was regarded merely as an unusual form of poliomyelitis or as a mysterious disease to which the name Australian X disease has