1. An attempt has been made to standardize the cultural and the serological work on influenza bacilli. As technique and knowledge improve cultural and serological characteristics may be shown to be different from those reported here. The results are constant enough for comparison as they were obtained under as nearly similar conditions as possible.
2. Of thirteen meningitic strains of Bacillus influenzæ isolated by different workers during a period of 7 years, eleven are alike culturally and fall into two groups by absorption of agglutinin tests; seven are in Group 1, three in Group 2, with one intermediate strain. Two strains stand alone culturally and serologically.
3. Four blood culture strains from children with pneumonia differ from each other culturally and serologically. When these strains show a relation culturally to members of the meningitic group this is not confirmed by serological reactions. When more respiratory strains are studied there may be found among them some similar culturally and serologically to the meningitic group.
4. Evidence has been set forth in favor of the possibility that a certain group of influenza bacilli may have risen to a level of pathogenicity to produce a disease picture known as influenzal meningitis. If this be true an attempt should be made to obtain a potent serum for treatment.