An unusual epidemic of diphtheria occurred in Austin, Texas, in the spring of 1922. Austin has about 40,000 inhabitants, including 4,200 students at the University of Texas. During January and February, ten cases of diphtheria in all were reported; eleven new cases developed by March 20, and twenty-three more by March 30. The disease was of extraordinary virulence, and laymen early called it black diphtheria. Very early in the disease, the appearance of the throat was peculiar. Both tonsils were covered with a thin, milky-looking membrane that shaded gradually into tissue that appeared normal without any sharp line of demarcation. The mucous membrane was not of the usual vivid red. The membrane which appeared in several parts of the throat simultaneously involved an unusual area, and it quickly developed a dirty, black appearance. In cases appearing early in the epidemic, repeated large doses of antitoxin were required, which in many