All active transmissible agent present in the nasopharynx in early cases of influenza has been found to produce definite and characteristic clinical reactions and pathological effects in rabbits as already described in an earlier publication.
The experiments here reported indicate that this active agent has the following properties.
1. The agent as it exists in the nasopharyngeal secretions in man, and in the lungs of rabbits injected with the human secretions, passes through Berkefeld V and N candles.
2. The filtered material produces the same effects on the circulating blood and on the lungs of rabbits as the unfiltered material.
3. The peculiar effects described as arising in the inoculated rabbit may also be induced in guinea pigs inoculated with the agent.
4. The agent responsible for the reaction on the blood and the lungs of rabbits withstands the action of glycerol in a sterile 50 per cent solution, for periods up to 9 months. The question must be left open at present whether the agent can withstand longer contact with the chemical. In two experiments after 10½ months contact the agent induced no observable changes in the blood and lungs of rabbits.