No affection is more common in temperate zones, probably, than that group of conditions, varying largely in clinical type and manifestations, which are classed together as "common colds." Relatively little investigation has, however, been directed toward the determination of their etiology. Their usual mild course and the absence of a fatal termination doubtless account for this fact. The tremendous economic loss caused by the incapacitation for work, from time to time, of a considerable

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... ion of the population, gives them an importance not always recognized. The reduced resistance following colds is likewise important in that it often predisposes to more severe infections, not alone confined to the respiratory tract. It would seem desirable to obtain more exact knowledge of the cause and mode of spread of common colds and influenza. The varied flora of the upper respiratory tract, under both normal and pathologic conditions makes the problem of the bacteriologic investigation a most complicated one. Recent studies by Bloomfield 1 have contributed materially to our knowledge of the bacteria which are normally present in the throat, and to the conditions which govern invasion by organisms not commonly present. Some circumstance other than the mere presence of a given bacterium seems to be necessary for the initiation of disease. Large amounts of bacterial growth, from cultures of various organisms, Sarcina lutea, Staphylococcus albus, B. coli 2 B. influenzae of Pfeiffer,S B. mucosus capsulatus of Friedlander 4 and Streptococcus hemolyticus,t were smeared on the tongue, pharynx, nasal septum and into the tonsillar crypts of pers-ons free from unusual abnormalities of the upper air passages. The various organisms disappeared as a rule within 24 hours. In no case was any demonstrable lesion or general reaction set up. The mechanical flushing action of the secretions seems undoubtedly the most important element in the disposal of bacteria introduced into the