Brucella abortus is a short, gram-negative bacillus, first described by Bang in 1897. Evans1 was the first to point out its close similarity to the organism described by Bruce in 1893 as Micrococcus melitensis. The organisms are indistinguishable morphologically, culturally or even by ordinary agglutination tests, but they can be distinguished by special agglutinin absorption tests. As would be supposed, the diseases caused by the two organisms cannot be differentiated clinically. Infection with Brucella abortus is widespread among the dairy cattle throughout the United States, and the organism has been isolated on several occasions from the milk of infected cows. The increasing number of case reports, beginning with Keefer's2 case in 1924, would tend to indicate that the infection in man is far from rare. Kern,3 in a recent article, has given a thorough review of the literature on the subject together with a very complete list of references.