THE ETIOLOGY OF INFLUENZA

The pandemic of influenza has been the subject of investigation to an unusual extent, not only because of its alarming character and widespread prevalence, but also because it has occurred at a time when great governmental agencies, like the medical departments of armies, were necessarily directed to the study. At the time of the pandemic of 1889-1890, the bacteriologic factors possibly associated with the disease were far from being recognized to the extent that is true at the present time. Pfeiffer's bacillus, the so-called B. influenzae, was not described until 1892. Even cursory acquaintance with the literature of influenza since that date cannot fail to indicate the uncertainty that has existed regarding the possible etiologic significance of this micro-organism. The most recent studies undertaken in connection with the outbreaks of influenza during the past year continue to give indications of this uncertainty.¹ Far from regarding the Pfeiffer bacillus as