The hemophilic and hemolytic organisms described by Davis, which he isolated from pathological urine, were non-symbiotic and non-pathogenic. Koch has described a similar organism from puerperal infection. Whether the hemophilic organism described by Thalhimer from the uterus in a case of puerperal infection, those found by Cohen in urethral discharge in one case and the pelvic exudate of another, and the findings of Kretz in pyelitis, Wright in pyelonephrosis and Klieneberger in cystitis cases, possibly refer to this same bacillus is, of course, uncertain. Pritchett and Stillman found a somewhat similar bacillus, which they called Bacillus X, from the mouths of 24 persons. It was hemophilic and hemolytic, stouter than B. influenzæ and showed long tangled threads in blood broth. It was non-pathogenic and is probably the same as Davis’ organism. Davis described another hemophilic bacillus from a patient with purulent foci which was non-hemolytic and non-symbiotic. It was grown from an abscess of the shoulder joint, the blood and the bronchial secretion of an infant. Cyanosis was a marked feature of this case. Paranhos described a hemophilic bacillus from meningitis, which, however, was Gram positive, and Moon reported an anærobic hemophilic bacillus from an infection of the ethmoid sinus. The work of Jordan would suggest that there may be two groups of B. influenzæ based on the indol production. _Morphology._—The morphology of B. influenzæ has received more than usual attention. In what we consider its characteristic form, it is an extremely small bacillus, usually single but sometimes in pairs, and not infrequently exhibiting polar staining. In direct smears, where there are many bacteria present, they are frequently arranged in the schools so frequently described. The development of thread forms is today considered quite characteristic for B. influenzæ. The organisms vary from moderately long bacillary forms to very long twisted or curled threads suggesting leptothrix. In such cultures chains of tiny bacilli are also quite often noted. At the other extreme we have exceedingly tiny coccoid forms, resembling in size the B. bronchisepticus, which, as Ferry has shown, are small enough to pass through many grades of filters.