Aphthous lesions of the mouth have been frequently described since the time of Hippocrates. Many opinions have been offered as to the cause, and the methods of treatment have been as varied as the authors. In a field in which opinions are so varied it is apparent that nothing conclusive is known or there would be more unanimity of opinion. Aphthae have been divided into many types, with fine points of differentiation, but nothing had been offered to bring the associated groups together until 1915, when Schamberg1 grouped "canker sores" with herpes simplex. Between 1919 and 1924 Goodpasture and Teague,2 Löwenstein3 and Gans,4 in their experimental work on viruses, stated the opinion that the herpes virus caused aphthae. These investigators, however, were unable to produce immunity in experimental animals to a known herpes virus, although lesions of the cornea and brain on inoculation were similar. Dodd,