=Pathogenesis.= By inoculation it infects chickens, pigeons and guinea-pigs, while rabbits and mice are refractory except to large doses. By ingestion it infects chickens and guinea-pigs but not pigeons. Infection takes place easily by the air passages. In all cases alike the lesions are concentrated in the intestines. _Lesions._ These are very similar in the different forms. The intestine is violently congested and contains a quantity of yellowish green mucopurulent or serous fluid. The mucosa is infiltrated, softened and even abraded by the desquamation of epithelium. The liver is greatly enlarged and softened and gorged with blood, and the gall bladder filled. The spleen is enlarged and pale, contrary to what is seen in fowl cholera, and the kidneys are congested. The heart is flaccid, soft, petechiated, and the pericardium is the seat of serous effusion. _Symptoms._ In the _acute form_ there is dullness, langor, inappetence, ardent thirst, pale comb, and greenish fæces. Later the feathers are erect, the wings and tail droop, the head sinks, the patient gapes frequently, walks unsteadily, and a liquid bluish green diarrhœa sets in, which later becomes yellow and bloody. The somnolence increases, the walk becomes more unsteady, or the patient sinks down with eyes half closed and refuses to rise. As the disease advances the comb becomes violet, the dark shade constantly increasing and a glairy grayish mucus is discharged from the nose and bill. The temperature which was at first raised 1° or 2°, falls 2° or 3° below the normal prior to death, which may be deferred to near the end of the second week. In the chronic cases the disease may drag along for three weeks, the emaciation, pallor and weakness constantly increasing and the feathers around the anus soiled and matted together by the fœtid liquid discharges. There may be remissions which go on to complete convalescence but more commonly an exacerbation occurs which proves fatal in a day or two. _Diagnosis._ From fowl cholera this may be distinguished by the fact that it is confined to one farm or flock of turkeys, chickens or ducks, proving most deadly in early summer, to the broods of the same spring, and at the commencement of the epizootic, and proving less and less so as time passes. The immunity of rabbits even when inoculated is a further distinguishing feature. From intestinal parasitism it is distinguished by the color of the discharges, and the absence of worms and their eggs from these liquids. _Mortality_ is often very high. Klein found it 80 per cent.