1. A strain of meningococci obtained directly from the spinal fluid of a patient has been propagated in serial passage in 10 to 12 day old chick embryos without change in its essential characteristics.
2. The chick embryo is susceptible to infection with the meningococcus, and, depending on its stage of development, reacts to the infection with more or less specific lesions.
3. In chick embryos of 15 days incubation, following the utilization of definite portals of entry, such as the nasopharynx, or by inoculation of the amniotic fluid or by inoculation of the body wall, the meningococcus is localized in specific areas, namely in the cranial sinuses, the lungs or meninges, or in all of these areas.
4. The lesions of the meningococcus infection in man, a septicemia, sinusitis, pneumonia and meningitis can be reproduced in the chick embryo by choosing embryos at the proper state of development and utilizing the various portals of entry experimentally available.