in 166, during the epidemic, the greek physician and writer galen traveled from rome to his home in asia minor. he returned to rome in 168 when summoned by the two augusti - the co-emperors marcus aurelius and lucius verus; he was present at the outbreak among troops stationed at aquileia in the winter of 168/69. galen briefly records observations and a description of the epidemic in the treatise "methodus medendi", and his other references to it are scattered among his voluminous writings. he describes the plague as "great" and of long duration and mentions fever, diarrhea, and pharyngitis, as well as a skin eruption, sometimes dry and sometimes pustular, appearing on the ninth day of the illness. the information provided by galen does not clearly define the nature of the disease, but scholars have generally preferred to diagnose it as smallpox.