In an extensive literature on the bacteriology of subacute bacterial endocarditis, there has been no mention of the hemolytic hemophilic bacilli. These organisms are closely related to the influenza bacilli, but they differ from them in one important property—their ability to hemolyze red blood cells. These influenza-like bacilli were first described in 1919 by Pritchett and Stillman,1who recovered them from the throats of healthy persons and grouped them under the term "Bacillus X." Rivers,2in 1920, suggested that they be considered hemolytic strains of B.influenzae. Later in the same year, Stillman and Bourne,3defined their cultural characteristics. Walker4encountered them in his work on hemolytic streptococcus carriers. Rivers and Leuschner,5in 1921, reported on their occurrence in normal throats. They recalled that in 1918, at Fort Sam Houston, members of the Pneumonia Commission had noted hemolytic colonies of gram-negative bacilli in throats of patients with measles. Bloomfield,6in