A strain of fowl coryza of slow onset was carried through 20 successive passages in susceptible birds over a period of approximately 19 months. During this period it retained its initial characteristics as did also a coryza of rapid onset which was similarly maintained. 88 per cent of 72 birds infected with the coryza of slow onset showed a nasal discharge after an incubation period of 12 days or more; the actual limits being 9 to 31 days. 98 per cent of 54 birds infected with the coryza of rapid onset showed a nasal discharge on the 1st or 2nd day after injection. The duration of both coryzas was prolonged.
Bacteriological examination indicated that Hemophilus gallinarum which is invariably present in the nasal exudate of birds infected with the coryza of rapid onset is not associated with the coryza of slow onset.