The fairly extensive study that has been made of the incidence of B. influenzæ in normal men and in cases of measles has clearly demonstrated that the proportion of carriers found in any group depends upon the prevalence of influenza in the group studied and that with the progress of the epidemic the percentage of carriers has steadily increased. When one considers that the opportunity for the dissemination of B. influenzæ by contact infection is almost unlimited during an epidemic of the proportions of that which has swept over the country, this is not at all surprising. That such a large number of normal individuals became carriers of B. influenzæ during the epidemic would seem to be sufficient evidence that actual dissemination does occur and to controvert the theory that in actual cases of influenza, conditions are established in the respiratory tract whereby B. influenzæ, always present in small numbers, is enabled to “grow out” and become the predominant organism. From a consideration of all the observations made as to the incidence of B. influenzæ in various conditions it would appear that the carrier condition is quite analogous to that found with many other bacteria, and may be divided into three groups: (_a_) acute carriers, those having influenza, (_b_) contact carriers, those who during epidemic times become temporary carriers of the organism without contracting the disease, and (_c_) chronic carriers, the relatively small number of normal individuals or those with chronic respiratory conditions who carry B. influenzæ over long periods of time. From the facts at hand this would seem to be the most probable explanation of the conditions found. It is certainly true that the established presence of pneumococcus, B. diphtheriæ, meningococcus and many other organisms in a varying proportion of normal individuals is not regarded as sufficient evidence to exclude them as the etiologic agents of the diseases which they cause.