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1. Studies of the cultivation of the virus of common cold in tissue medium, and the capacity of the culture virus to induce infection in human volunteers are reported. 2. Detailed descriptions are given of the methods employed to isolate the virus, preserve and cultivate it, and to test its activity in human volunteers. 3. The virus of common cold can easily be isolated from properly selected patients and cultivated in tissue medium. 4. When kept in the original nasopharyngeal washings, the virus will survive at ice box temperature under anaerobic conditions for at least 13 days. 5. If the nasopharyngeal washings are frozen and dried in vacuo, the virus retains its activity for at least 4 months. 6. The virus of common cold has been proven to multiply in medium containing chick embryo tissue. Such cultures retain their capacity to produce typical infections in human beings for many transfers involving a period of several months. Attempts to cultivate the virus have been successful in seven out of eight instances. 7. Prolonged cultivation of the virus in tissue medium eventually leads to a loss of activity. 8. Strains of virus under cultivation maintain their potency best when transfers are made at 2 and 3 day intervals. 9. After removal from the incubator a culture of virus rapidly becomes inactive whether it be kept under seal in the ice box or frozen and dried in vacuo. 10. The destructive action of the medium can be prevented if the culture is mixed with gum acacia before freezing and drying in vacuo.

1. Evidence is presented indicating the presence of a filtrable virus in the nasopharyngeal secretions of individuals suffering from influenza. 2. An attempt to transfer influenza from one human being to another by means of filtered nasopharyngeal washings resulted in the production in the inoculated volunteer of a common cold. 3. A filtrable agent has been cultivated in tissue medium from the filtered nasopharyngeal washings of patients with influenza. 4. Inoculation of the cultivated virus into human volunteers results for the most part in the production of a severe common cold with a tendency to pronounced constitutional reaction. 5. In one instance following inoculation of culture virus an infection clinically resembling influenza has been produced. 6. The more closely the source of the virus approached the type of epidemic influenza, the more likely the virus was to provoke constitutional symptoms. 7. The presence of certain pathogenic bacteria in the upper respiratory tract of inoculated individuals was not observed to modify the course or character of the experimental infection. 8. On prolonged cultivation the virus loses the capacity to infect human volunteers.

Mice have been extensively employed in the study of the virus of human influenza since the discovery by Andrewes, Laidlaw, and Smith,1and by Francis2that these animals are susceptible to intranasal inoculation of ferret-passed virus. Francis3 has recently shown that influenza virus cultivated in the chorio-allantoic membrane of the developing chick embryo is pathogenic for mice and does not require ferret passage to raise its virulence. Many of the immunological studies of influenza virus have been made by means of protection tests using mice as test animals. It is obvious, therefore, that if the virus of the common cold could be made virulent for mice, a similar and valuable immunological study of this virus could be made.After a number of preliminary failures in attempts to infect mice by intranasal inoculation of the virus of common cold, we began, during the summer of 1936, to use virus for inoculation which was being cultivated in the chorio-allantoic membrane of the chick embryo. By this means, with comparatively little difficulty, 3 different strains of virus were established in mice and could be passed in series by intranasal inoculation of emulsions of infected lung. After the few passages necessary to establish the strains, all 3 produced fairly uniform lesions in the lungs. The mortality rate was much less than that reported for human influenza virus, only about 10% of the mice dying in 4 or 5 days. About 75%, however, showed fairly extensive pulmonary consolidation at autopsy. The areas of pulmonary consolidation were plum colored, often involving a whole lobe, and their gross appearance closely resembled that seen in mice infected with human influenza virus. The serological relationship to one another of the 3 strains of common cold virus was studied by means of protection tests in mice.

For many years the etiology of influenza has been the subject of an interesting and continuous discussion. A number of microscopically visible organisms have been assigned a certain causative relationship to this disease. The most important of these microorganisms is H. influenzae, the significance of whose relationship to influenza was first brought out by Pfeiffer. This organism has continued to hold a prominent position on the stage of debate concerning the disease. Another question that has led to much discussion is the degree of uniformity of nature of the pathological and clinical entity described as influenza. Interest in this regard has largely centered upon the identity or non-identity of the so-called pandemic and inter-pandemic forms of the disease. Clinically, examples of the disease in pandemic and in inter-pandemic periods may resemble each other so closely as to be indistinguishable. Whether they are the same condition from an etiologic standpoint can not, however, as yet be answered.In recent years, with increasing knowledge of filterable viruses, this group of micro-organisms has been prominently considered in discussions of the etiology of influenza. Some evidence1, 2, 3, 4, 5has already been brought out tending to implicate them in the disease and it is with this aspect of influenza that the present work is concerned.During an outbreak of influenza of the inter-pandemic type in the winter of 1930, an effort was made to communicate the disease to chimpanzees by means of bacteria-free filtrates of nasopharyngeal washings obtained from patients with typical attacks of the disease. The washings were obtained during the first 36 hours of the attack, passed rapidly through Seitz filters and inoculated intranasally in chimpanzees.

We have reported the successful cultivation of the virus of the common cold in an anaerobic medium containing chick-embryo tissue.1,2Our purpose in the present communication is to describe the cultivation of this virus in the chorio-allantoic membrane of the developing chick-embryo.This technic for the cultivation of the viruses of infectious diseases was developed by Woodruff and Goodpasture3for the propagation of fowl pox virus, and later successfully applied by them and others to a number of different viruses. Wilson Smith4reported the cultivation of a mouse-passage strain of human influenza virus by this means. A more elaborate series of similar experiments has already been recorded by Burnet.5Our own experiment was as follows: In September, 1936, a nasal washing was obtained from an individual with a typical acute head cold of less than 24 hours' duration. The washing was passed rapidly through a Seitz filter, and concentrated to one-fourth its original volume by vacuum distillation. Two-tenths cc. of this bacteria-free filtrate, almost immediately after its isolation from the human source, were inoculated into the chorio-allantoic membranes of 12-day chick-embryos according to the technic described by previous authors. At the end of 2 or 3 days the membranes were removed and ground up with non-toxic broth so as to make a suspension of approximately 20%; 0.2 cc. of this were inoculated into each of a second series of eggs. Similarly these membranes were ground up and inoculated into a third. It is noteworthy that the small opaque foci visible on the membranes and which Burnet5described as resulting from the cultivation of influenza virus were also observed by us.