_Incubation._ This varies from 18 to 48 hours, the usual being 24 hours. _Symptoms._ In some _fulminant cases_ the animal is found dead a few hours after apparently blooming health; it may even have died on the nest or fallen dead from the roost. Cadeac speaks of transient symptoms even in such cases—extreme dulness, prostration, somnolence, seclusion in a cool, dark place, ruffling of feathers, sinking of the head between the wings, drooping, trailing wings and tail, violet comb, gaping, discharge of glairy mucus from the bill, convulsions and death. These symptoms last from two to five hours. In _acute_ but less fulminant forms there is loss of appetite, depression, debility, apathy, erection of the feathers, sinking of the head, swaying when made to walk, drooping wings and tail, sitting on the breast, convulsive tremblings, discharge of filmy or frothy mucus by the nose or mouth, vomiting, hyperthermia (108° to 111° F. ), sighing, breathing, inflation of the crop, violet colored comb, wattles and mucosæ, great thirst and diarrhœa, at first pultaceous and light yellow, later glairy, green and fetid. The feathers round the anus become soaked and matted with the discharge. Temperature becomes subnormal, the patient falls and is unable to rise, and finally dies in a stupor or convulsions, the illness having lasted 1 to 3 days. _Milder cases_ occurring chiefly towards the end of an outbreak when the less susceptible animals only are left, or when the microbe has become less virulent, show a larger ratio of recoveries. These show a lack of spirit and vigor, impaired appetite, diarrhœa, emaciation, dulness, prostration, moping, ruffling of the plumes, dark discoloration of the comb, and often swelling of one or more important joints (femoro-tibial, etc.). These may burst and discharge a reddish pus, or simply form dark or grayish swellings. These cases may drag along for a week or more and finally die in marasmus. The minute bacillus is not obtainable from these (Lignieres). Cases inoculated in the pectoral muscles with only one or two microbes usually have only a circumscribed slough, with loss of condition, and after the elimination of the slough and the healing of the sore the bird proves immune.