Pneumococci, H. influenzae, and S. hemolyticus are known to be frequent inhabitants of the upper respiratory tract, but most workers have not recognized any definite relationships between their presence and coryza, sore throat, influenzal, and sinusitis attacks (2–5). Dochez, Shibley, and Mills, however, in their experimental studies of common cold, state that in both the spontaneous and experimentally induced "colds" in anthropoid apes, the "most significant change observed has been the increase of activity on the part of the potential pathogens habitually present in the throat flora. Coincident with the appearance of symptoms, pneumococci, S. hemolyticus, and B. pfeifferi have developed in greatly increased numbers and have spread over a wide area of the nasopharyngeal mucous membranes. These organisms became at this time conspicuous even in the nose, where they are seldom or never present under normal conditions. The same phenomena have not been observed in human beings" (6, 7).
The essential facts of the present observations are that persons free of pneumococci, H. influenzae, and S. hemolyticus are in general free of coryza, sore throat, influenzal and sinus attacks; that persons who are occasional or periodic carriers of these organisms may be negative on tests over long healthy periods, but generally become positive during or following attacks and subsequently become negative again; finally, that persons who are chronic carriers show during these illnesses increasing numbers of organisms in the throat and extension of the organisms to the nose.
That these organisms may be the actual incitants has been claimed by Park (8); that they are secondary invaders is the view of Shibley, Mills, and Dochez who state as a result of their experimental work on this subject that "the most important significance of viruses of this type [common cold] seems to lie in their capacity to incite activity on the part of the more dangerous pathogenic organisms that infect the upper respiratory tract" (7). The present observations bring out the intimate relationship between these pathogens and upper respiratory tract symptoms, but do not disclose the nature of this relationship.
Finally, an addition has been made to the knowledge of the mode of spread of these organisms. A focus of growth and dissemination has been determined in the nasal passages and throat of individuals with chronic upper respiratory tract disease and increases in numbers of the organisms at the focus and their spread to contacts have been related to the winter season and to the occurrence of symptoms in the carrier. The observations suggest that the dosage of these organisms in a community is controlled by the resistance of the carrier and of the contacts. This view is in agreement with the facts derived from studies of native animal infections (9).